walsender.c File Reference

#include "postgres.h"
#include <signal.h>
#include <unistd.h>
#include "access/timeline.h"
#include "access/transam.h"
#include "access/twophase.h"
#include "access/xact.h"
#include "access/xlog_internal.h"
#include "access/xlogreader.h"
#include "access/xlogrecovery.h"
#include "access/xlogutils.h"
#include "backup/basebackup.h"
#include "backup/basebackup_incremental.h"
#include "catalog/pg_authid.h"
#include "catalog/pg_type.h"
#include "commands/defrem.h"
#include "funcapi.h"
#include "libpq/libpq.h"
#include "libpq/pqformat.h"
#include "libpq/protocol.h"
#include "miscadmin.h"
#include "nodes/replnodes.h"
#include "pgstat.h"
#include "postmaster/interrupt.h"
#include "replication/decode.h"
#include "replication/logical.h"
#include "replication/slotsync.h"
#include "replication/slot.h"
#include "replication/snapbuild.h"
#include "replication/syncrep.h"
#include "replication/walreceiver.h"
#include "replication/walsender.h"
#include "replication/walsender_private.h"
#include "storage/condition_variable.h"
#include "storage/aio_subsys.h"
#include "storage/fd.h"
#include "storage/ipc.h"
#include "storage/pmsignal.h"
#include "storage/proc.h"
#include "storage/procarray.h"
#include "storage/subsystems.h"
#include "tcop/dest.h"
#include "tcop/tcopprot.h"
#include "utils/acl.h"
#include "utils/builtins.h"
#include "utils/guc.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/pg_lsn.h"
#include "utils/pgstat_internal.h"
#include "utils/ps_status.h"
#include "utils/timeout.h"
#include "utils/timestamp.h"
#include "utils/wait_event.h"

Include dependency graph for walsender.c:

Go to the source code of this file.

Data Structures
struct	WalTimeSample
struct	LagTracker

Macros
#define	WALSENDER_STATS_FLUSH_INTERVAL   1000
#define	MAX_SEND_SIZE   (XLOG_BLCKSZ * 16)
#define	LAG_TRACKER_BUFFER_SIZE   8192
#define	READ_REPLICATION_SLOT_COLS   3
#define	WALSND_LOGICAL_LAG_TRACK_INTERVAL_MS   1000
#define	PG_STAT_GET_WAL_SENDERS_COLS   12

Typedefs
typedef void(*	WalSndSendDataCallback) (void)

Functions
static void	WalSndShmemRequest (void *arg)
static void	WalSndShmemInit (void *arg)
static void	WalSndLastCycleHandler (SIGNAL_ARGS)
static void	WalSndLoop (WalSndSendDataCallback send_data)
static void	InitWalSenderSlot (void)
static void	WalSndKill (int code, Datum arg)
static pg_noreturn void	WalSndShutdown (void)
static void	XLogSendPhysical (void)
static void	XLogSendLogical (void)
static pg_noreturn void	WalSndDoneImmediate (void)
static void	WalSndDone (WalSndSendDataCallback send_data)
static void	IdentifySystem (void)
static void	UploadManifest (void)
static bool	HandleUploadManifestPacket (StringInfo buf, off_t *offset, IncrementalBackupInfo *ib)
static void	ReadReplicationSlot (ReadReplicationSlotCmd *cmd)
static void	CreateReplicationSlot (CreateReplicationSlotCmd *cmd)
static void	DropReplicationSlot (DropReplicationSlotCmd *cmd)
static void	StartReplication (StartReplicationCmd *cmd)
static void	StartLogicalReplication (StartReplicationCmd *cmd)
static void	ProcessStandbyMessage (void)
static void	ProcessStandbyReplyMessage (void)
static void	ProcessStandbyHSFeedbackMessage (void)
static void	ProcessStandbyPSRequestMessage (void)
static void	ProcessRepliesIfAny (void)
static void	ProcessPendingWrites (void)
static void	WalSndKeepalive (bool requestReply, XLogRecPtr writePtr)
static void	WalSndKeepaliveIfNecessary (void)
static void	WalSndCheckTimeOut (void)
static void	WalSndCheckShutdownTimeout (void)
static long	WalSndComputeSleeptime (TimestampTz now)
static void	WalSndWait (uint32 socket_events, long timeout, uint32 wait_event)
static void	WalSndPrepareWrite (LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid, bool last_write)
static void	WalSndWriteData (LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid, bool last_write)
static void	WalSndUpdateProgress (LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid, bool skipped_xact)
static XLogRecPtr	WalSndWaitForWal (XLogRecPtr loc)
static void	LagTrackerWrite (XLogRecPtr lsn, TimestampTz local_flush_time)
static TimeOffset	LagTrackerRead (int head, XLogRecPtr lsn, TimestampTz now)
static bool	TransactionIdInRecentPast (TransactionId xid, uint32 epoch)
static void	WalSndSegmentOpen (XLogReaderState *state, XLogSegNo nextSegNo, TimeLineID *tli_p)
void	InitWalSender (void)
void	WalSndErrorCleanup (void)
static void	SendTimeLineHistory (TimeLineHistoryCmd *cmd)
static int	logical_read_xlog_page (XLogReaderState *state, XLogRecPtr targetPagePtr, int reqLen, XLogRecPtr targetRecPtr, char *cur_page)
static void	parseCreateReplSlotOptions (CreateReplicationSlotCmd *cmd, bool *reserve_wal, CRSSnapshotAction *snapshot_action, bool *two_phase, bool *failover)
static void	AlterReplicationSlot (AlterReplicationSlotCmd *cmd)
static void	WalSndHandleConfigReload (void)
void	PhysicalWakeupLogicalWalSnd (void)
static bool	NeedToWaitForStandbys (XLogRecPtr flushed_lsn, uint32 *wait_event)
static bool	NeedToWaitForWal (XLogRecPtr target_lsn, XLogRecPtr flushed_lsn, uint32 *wait_event)
bool	exec_replication_command (const char *cmd_string)
static void	PhysicalConfirmReceivedLocation (XLogRecPtr lsn)
static void	PhysicalReplicationSlotNewXmin (TransactionId feedbackXmin, TransactionId feedbackCatalogXmin)
XLogRecPtr	GetStandbyFlushRecPtr (TimeLineID *tli)
void	WalSndRqstFileReload (void)
void	HandleWalSndInitStopping (void)
void	WalSndSignals (void)
void	WalSndWakeup (bool physical, bool logical)
void	WalSndInitStopping (void)
void	WalSndWaitStopping (void)
void	WalSndSetState (WalSndState state)
static const char *	WalSndGetStateString (WalSndState state)
static Interval *	offset_to_interval (TimeOffset offset)
Datum	pg_stat_get_wal_senders (PG_FUNCTION_ARGS)

Variables
WalSndCtlData *	WalSndCtl = NULL
const ShmemCallbacks	WalSndShmemCallbacks
WalSnd *	MyWalSnd = NULL
bool	am_walsender = false
bool	am_cascading_walsender = false
bool	am_db_walsender = false
int	max_wal_senders = 10
int	wal_sender_timeout = 60 * 1000
int	wal_sender_shutdown_timeout = -1
bool	log_replication_commands = false
bool	wake_wal_senders = false
static XLogReaderState *	xlogreader = NULL
static IncrementalBackupInfo *	uploaded_manifest = NULL
static MemoryContext	uploaded_manifest_mcxt = NULL
static TimeLineID	sendTimeLine = 0
static TimeLineID	sendTimeLineNextTLI = 0
static bool	sendTimeLineIsHistoric = false
static XLogRecPtr	sendTimeLineValidUpto = InvalidXLogRecPtr
static XLogRecPtr	sentPtr = InvalidXLogRecPtr
static StringInfoData	output_message
static StringInfoData	reply_message
static StringInfoData	tmpbuf
static TimestampTz	last_processing = 0
static TimestampTz	last_reply_timestamp = 0
static bool	waiting_for_ping_response = false
static TimestampTz	shutdown_request_timestamp = 0
static bool	shutdown_stream_done_queued = false
static bool	streamingDoneSending
static bool	streamingDoneReceiving
static bool	WalSndCaughtUp = false
static volatile sig_atomic_t	got_SIGUSR2 = false
static volatile sig_atomic_t	got_STOPPING = false
static volatile sig_atomic_t	replication_active = false
static LogicalDecodingContext *	logical_decoding_ctx = NULL
static LagTracker *	lag_tracker

Macro Definition Documentation

LAG_TRACKER_BUFFER_SIZE

#define LAG_TRACKER_BUFFER_SIZE   8192

Definition at line 253 of file walsender.c.

MAX_SEND_SIZE

#define MAX_SEND_SIZE   (XLOG_BLCKSZ * 16)

Definition at line 118 of file walsender.c.

PG_STAT_GET_WAL_SENDERS_COLS

#define PG_STAT_GET_WAL_SENDERS_COLS   12

READ_REPLICATION_SLOT_COLS

#define READ_REPLICATION_SLOT_COLS   3

WALSENDER_STATS_FLUSH_INTERVAL

#define WALSENDER_STATS_FLUSH_INTERVAL   1000

Definition at line 107 of file walsender.c.

WALSND_LOGICAL_LAG_TRACK_INTERVAL_MS

#define WALSND_LOGICAL_LAG_TRACK_INTERVAL_MS   1000

Typedef Documentation

WalSndSendDataCallback

typedef void(* WalSndSendDataCallback) (void)

Definition at line 285 of file walsender.c.

Function Documentation

AlterReplicationSlot()

static void AlterReplicationSlot ( AlterReplicationSlotCmd *  cmd )

static

Definition at line 1472 of file walsender.c.

{
    bool        failover_given = false;
    bool        two_phase_given = false;
    bool        failover;
    bool        two_phase;
 
    /* Parse options */
    foreach_ptr(DefElem, defel, cmd->options)
    {
        if (strcmp(defel->defname, "failover") == 0)
        {
            if (failover_given)
                ereport(ERROR,
                        (errcode(ERRCODE_SYNTAX_ERROR),
                         errmsg("conflicting or redundant options")));
            failover_given = true;
            failover = defGetBoolean(defel);
        }
        else if (strcmp(defel->defname, "two_phase") == 0)
        {
            if (two_phase_given)
                ereport(ERROR,
                        (errcode(ERRCODE_SYNTAX_ERROR),
                         errmsg("conflicting or redundant options")));
            two_phase_given = true;
            two_phase = defGetBoolean(defel);
        }
        else
            elog(ERROR, "unrecognized option: %s", defel->defname);
    }
 
    ReplicationSlotAlter(cmd->slotname,
                         failover_given ? &failover : NULL,
                         two_phase_given ? &two_phase : NULL);
}

References defGetBoolean(), elog, ereport, errcode(), errmsg, ERROR, failover, fb(), foreach_ptr, AlterReplicationSlotCmd::options, ReplicationSlotAlter(), AlterReplicationSlotCmd::slotname, and two_phase.

Referenced by exec_replication_command().

CreateReplicationSlot()

static void CreateReplicationSlot ( CreateReplicationSlotCmd *  cmd )

static

Definition at line 1249 of file walsender.c.

{
    const char *snapshot_name = NULL;
    char        xloc[MAXFNAMELEN];
    char       *slot_name;
    bool        reserve_wal = false;
    bool        two_phase = false;
    bool        failover = false;
    CRSSnapshotAction snapshot_action = CRS_EXPORT_SNAPSHOT;
    DestReceiver *dest;
    TupOutputState *tstate;
    TupleDesc   tupdesc;
    Datum       values[4];
    bool        nulls[4] = {0};
 
    Assert(!MyReplicationSlot);
 
    parseCreateReplSlotOptions(cmd, &reserve_wal, &snapshot_action, &two_phase,
                               &failover);
 
    if (cmd->kind == REPLICATION_KIND_PHYSICAL)
    {
        ReplicationSlotCreate(cmd->slotname, false,
                              cmd->temporary ? RS_TEMPORARY : RS_PERSISTENT,
                              false, false, false, false);
 
        if (reserve_wal)
        {
            ReplicationSlotReserveWal();
 
            ReplicationSlotMarkDirty();
 
            /* Write this slot to disk if it's a permanent one. */
            if (!cmd->temporary)
                ReplicationSlotSave();
        }
    }
    else
    {
        LogicalDecodingContext *ctx;
        bool        need_full_snapshot = false;
 
        Assert(cmd->kind == REPLICATION_KIND_LOGICAL);
 
        CheckLogicalDecodingRequirements(false);
 
        /*
         * Initially create persistent slot as ephemeral - that allows us to
         * nicely handle errors during initialization because it'll get
         * dropped if this transaction fails. We'll make it persistent at the
         * end. Temporary slots can be created as temporary from beginning as
         * they get dropped on error as well.
         */
        ReplicationSlotCreate(cmd->slotname, true,
                              cmd->temporary ? RS_TEMPORARY : RS_EPHEMERAL,
                              two_phase, false, failover, false);
 
        /*
         * Do options check early so that we can bail before calling the
         * DecodingContextFindStartpoint which can take long time.
         */
        if (snapshot_action == CRS_EXPORT_SNAPSHOT)
        {
            if (IsTransactionBlock())
                ereport(ERROR,
                /*- translator: %s is a CREATE_REPLICATION_SLOT statement */
                        (errmsg("%s must not be called inside a transaction",
                                "CREATE_REPLICATION_SLOT ... (SNAPSHOT 'export')")));
 
            need_full_snapshot = true;
        }
        else if (snapshot_action == CRS_USE_SNAPSHOT)
        {
            if (!IsTransactionBlock())
                ereport(ERROR,
                /*- translator: %s is a CREATE_REPLICATION_SLOT statement */
                        (errmsg("%s must be called inside a transaction",
                                "CREATE_REPLICATION_SLOT ... (SNAPSHOT 'use')")));
 
            if (XactIsoLevel != XACT_REPEATABLE_READ)
                ereport(ERROR,
                /*- translator: %s is a CREATE_REPLICATION_SLOT statement */
                        (errmsg("%s must be called in REPEATABLE READ isolation mode transaction",
                                "CREATE_REPLICATION_SLOT ... (SNAPSHOT 'use')")));
            if (!XactReadOnly)
                ereport(ERROR,
                /*- translator: %s is a CREATE_REPLICATION_SLOT statement */
                        (errmsg("%s must be called in a read-only transaction",
                                "CREATE_REPLICATION_SLOT ... (SNAPSHOT 'use')")));
 
            if (FirstSnapshotSet)
                ereport(ERROR,
                /*- translator: %s is a CREATE_REPLICATION_SLOT statement */
                        (errmsg("%s must be called before any query",
                                "CREATE_REPLICATION_SLOT ... (SNAPSHOT 'use')")));
 
            if (IsSubTransaction())
                ereport(ERROR,
                /*- translator: %s is a CREATE_REPLICATION_SLOT statement */
                        (errmsg("%s must not be called in a subtransaction",
                                "CREATE_REPLICATION_SLOT ... (SNAPSHOT 'use')")));
 
            need_full_snapshot = true;
        }
 
        /*
         * Ensure the logical decoding is enabled before initializing the
         * logical decoding context.
         */
        EnsureLogicalDecodingEnabled();
        Assert(IsLogicalDecodingEnabled());
 
        ctx = CreateInitDecodingContext(cmd->plugin, NIL, need_full_snapshot,
                                        false,
                                        InvalidXLogRecPtr,
                                        XL_ROUTINE(.page_read = logical_read_xlog_page,
                                                   .segment_open = WalSndSegmentOpen,
                                                   .segment_close = wal_segment_close),
                                        WalSndPrepareWrite, WalSndWriteData,
                                        WalSndUpdateProgress);
 
        /*
         * Signal that we don't need the timeout mechanism. We're just
         * creating the replication slot and don't yet accept feedback
         * messages or send keepalives. As we possibly need to wait for
         * further WAL the walsender would otherwise possibly be killed too
         * soon.
         */
        last_reply_timestamp = 0;
 
        /* build initial snapshot, might take a while */
        DecodingContextFindStartpoint(ctx);
 
        /*
         * Export or use the snapshot if we've been asked to do so.
         *
         * NB. We will convert the snapbuild.c kind of snapshot to normal
         * snapshot when doing this.
         */
        if (snapshot_action == CRS_EXPORT_SNAPSHOT)
        {
            snapshot_name = SnapBuildExportSnapshot(ctx->snapshot_builder);
        }
        else if (snapshot_action == CRS_USE_SNAPSHOT)
        {
            Snapshot    snap;
 
            snap = SnapBuildInitialSnapshot(ctx->snapshot_builder);
            RestoreTransactionSnapshot(snap, MyProc);
        }
 
        /* don't need the decoding context anymore */
        FreeDecodingContext(ctx);
 
        if (!cmd->temporary)
            ReplicationSlotPersist();
    }
 
    snprintf(xloc, sizeof(xloc), "%X/%08X",
             LSN_FORMAT_ARGS(MyReplicationSlot->data.confirmed_flush));
 
    dest = CreateDestReceiver(DestRemoteSimple);
 
    /*----------
     * Need a tuple descriptor representing four columns:
     * - first field: the slot name
     * - second field: LSN at which we became consistent
     * - third field: exported snapshot's name
     * - fourth field: output plugin
     */
    tupdesc = CreateTemplateTupleDesc(4);
    TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 1, "slot_name",
                              TEXTOID, -1, 0);
    TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 2, "consistent_point",
                              TEXTOID, -1, 0);
    TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 3, "snapshot_name",
                              TEXTOID, -1, 0);
    TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 4, "output_plugin",
                              TEXTOID, -1, 0);
    TupleDescFinalize(tupdesc);
 
    /* prepare for projection of tuples */
    tstate = begin_tup_output_tupdesc(dest, tupdesc, &TTSOpsVirtual);
 
    /* slot_name */
    slot_name = NameStr(MyReplicationSlot->data.name);
    values[0] = CStringGetTextDatum(slot_name);
 
    /* consistent wal location */
    values[1] = CStringGetTextDatum(xloc);
 
    /* snapshot name, or NULL if none */
    if (snapshot_name != NULL)
        values[2] = CStringGetTextDatum(snapshot_name);
    else
        nulls[2] = true;
 
    /* plugin, or NULL if none */
    if (cmd->plugin != NULL)
        values[3] = CStringGetTextDatum(cmd->plugin);
    else
        nulls[3] = true;
 
    /* send it to dest */
    do_tup_output(tstate, values, nulls);
    end_tup_output(tstate);
 
    ReplicationSlotRelease();
}

References Assert, begin_tup_output_tupdesc(), CheckLogicalDecodingRequirements(), ReplicationSlotPersistentData::confirmed_flush, CreateDestReceiver(), CreateInitDecodingContext(), CreateTemplateTupleDesc(), CRS_EXPORT_SNAPSHOT, CRS_USE_SNAPSHOT, CStringGetTextDatum, ReplicationSlot::data, DecodingContextFindStartpoint(), DestRemoteSimple, do_tup_output(), end_tup_output(), EnsureLogicalDecodingEnabled(), ereport, errmsg, ERROR, failover, fb(), FirstSnapshotSet, FreeDecodingContext(), InvalidXLogRecPtr, IsLogicalDecodingEnabled(), IsSubTransaction(), IsTransactionBlock(), CreateReplicationSlotCmd::kind, last_reply_timestamp, logical_read_xlog_page(), LSN_FORMAT_ARGS, MAXFNAMELEN, MyProc, MyReplicationSlot, ReplicationSlotPersistentData::name, NameStr, NIL, parseCreateReplSlotOptions(), CreateReplicationSlotCmd::plugin, REPLICATION_KIND_LOGICAL, REPLICATION_KIND_PHYSICAL, ReplicationSlotCreate(), ReplicationSlotMarkDirty(), ReplicationSlotPersist(), ReplicationSlotRelease(), ReplicationSlotReserveWal(), ReplicationSlotSave(), RestoreTransactionSnapshot(), RS_EPHEMERAL, RS_PERSISTENT, RS_TEMPORARY, CreateReplicationSlotCmd::slotname, SnapBuildExportSnapshot(), SnapBuildInitialSnapshot(), LogicalDecodingContext::snapshot_builder, snprintf, CreateReplicationSlotCmd::temporary, TTSOpsVirtual, TupleDescFinalize(), TupleDescInitBuiltinEntry(), two_phase, values, wal_segment_close(), WalSndPrepareWrite(), WalSndSegmentOpen(), WalSndUpdateProgress(), WalSndWriteData(), XACT_REPEATABLE_READ, XactIsoLevel, XactReadOnly, and XL_ROUTINE.

Referenced by exec_replication_command(), main(), and StartLogStreamer().

DropReplicationSlot()

static void DropReplicationSlot ( DropReplicationSlotCmd *  cmd )

static

Definition at line 1463 of file walsender.c.

{
    ReplicationSlotDrop(cmd->slotname, !cmd->wait);
}

References ReplicationSlotDrop(), DropReplicationSlotCmd::slotname, and DropReplicationSlotCmd::wait.

Referenced by exec_replication_command(), and main().

exec_replication_command()

bool exec_replication_command

(

const char *

cmd_string

)

Definition at line 2087 of file walsender.c.

{
    yyscan_t    scanner;
    int         parse_rc;
    Node       *cmd_node;
    const char *cmdtag;
    MemoryContext old_context = CurrentMemoryContext;
 
    /* We save and re-use the cmd_context across calls */
    static MemoryContext cmd_context = NULL;
 
    /*
     * If WAL sender has been told that shutdown is getting close, switch its
     * status accordingly to handle the next replication commands correctly.
     */
    if (got_STOPPING)
        WalSndSetState(WALSNDSTATE_STOPPING);
 
    /*
     * Throw error if in stopping mode.  We need prevent commands that could
     * generate WAL while the shutdown checkpoint is being written.  To be
     * safe, we just prohibit all new commands.
     */
    if (MyWalSnd->state == WALSNDSTATE_STOPPING)
        ereport(ERROR,
                (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                 errmsg("cannot execute new commands while WAL sender is in stopping mode")));
 
    /*
     * CREATE_REPLICATION_SLOT ... LOGICAL exports a snapshot until the next
     * command arrives. Clean up the old stuff if there's anything.
     */
    SnapBuildClearExportedSnapshot();
 
    CHECK_FOR_INTERRUPTS();
 
    /*
     * Prepare to parse and execute the command.
     *
     * Because replication command execution can involve beginning or ending
     * transactions, we need a working context that will survive that, so we
     * make it a child of TopMemoryContext.  That in turn creates a hazard of
     * long-lived memory leaks if we lose track of the working context.  We
     * deal with that by creating it only once per walsender, and resetting it
     * for each new command.  (Normally this reset is a no-op, but if the
     * prior exec_replication_command call failed with an error, it won't be.)
     *
     * This is subtler than it looks.  The transactions we manage can extend
     * across replication commands, indeed SnapBuildClearExportedSnapshot
     * might have just ended one.  Because transaction exit will revert to the
     * memory context that was current at transaction start, we need to be
     * sure that that context is still valid.  That motivates re-using the
     * same cmd_context rather than making a new one each time.
     */
    if (cmd_context == NULL)
        cmd_context = AllocSetContextCreate(TopMemoryContext,
                                            "Replication command context",
                                            ALLOCSET_DEFAULT_SIZES);
    else
        MemoryContextReset(cmd_context);
 
    MemoryContextSwitchTo(cmd_context);
 
    replication_scanner_init(cmd_string, &scanner);
 
    /*
     * Is it a WalSender command?
     */
    if (!replication_scanner_is_replication_command(scanner))
    {
        /* Nope; clean up and get out. */
        replication_scanner_finish(scanner);
 
        MemoryContextSwitchTo(old_context);
        MemoryContextReset(cmd_context);
 
        /* XXX this is a pretty random place to make this check */
        if (MyDatabaseId == InvalidOid)
            ereport(ERROR,
                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                     errmsg("cannot execute SQL commands in WAL sender for physical replication")));
 
        /* Tell the caller that this wasn't a WalSender command. */
        return false;
    }
 
    /*
     * Looks like a WalSender command, so parse it.
     */
    parse_rc = replication_yyparse(&cmd_node, scanner);
    if (parse_rc != 0)
        ereport(ERROR,
                (errcode(ERRCODE_SYNTAX_ERROR),
                 errmsg_internal("replication command parser returned %d",
                                 parse_rc)));
    replication_scanner_finish(scanner);
 
    /*
     * Report query to various monitoring facilities.  For this purpose, we
     * report replication commands just like SQL commands.
     */
    debug_query_string = cmd_string;
 
    pgstat_report_activity(STATE_RUNNING, cmd_string);
 
    /*
     * Log replication command if log_replication_commands is enabled. Even
     * when it's disabled, log the command with DEBUG1 level for backward
     * compatibility.
     */
    ereport(log_replication_commands ? LOG : DEBUG1,
            (errmsg("received replication command: %s", cmd_string)));
 
    /*
     * Disallow replication commands in aborted transaction blocks.
     */
    if (IsAbortedTransactionBlockState())
        ereport(ERROR,
                (errcode(ERRCODE_IN_FAILED_SQL_TRANSACTION),
                 errmsg("current transaction is aborted, "
                        "commands ignored until end of transaction block")));
 
    CHECK_FOR_INTERRUPTS();
 
    /*
     * Allocate buffers that will be used for each outgoing and incoming
     * message.  We do this just once per command to reduce palloc overhead.
     */
    initStringInfo(&output_message);
    initStringInfo(&reply_message);
    initStringInfo(&tmpbuf);
 
    switch (cmd_node->type)
    {
        case T_IdentifySystemCmd:
            cmdtag = "IDENTIFY_SYSTEM";
            set_ps_display(cmdtag);
            IdentifySystem();
            EndReplicationCommand(cmdtag);
            break;
 
        case T_ReadReplicationSlotCmd:
            cmdtag = "READ_REPLICATION_SLOT";
            set_ps_display(cmdtag);
            ReadReplicationSlot((ReadReplicationSlotCmd *) cmd_node);
            EndReplicationCommand(cmdtag);
            break;
 
        case T_BaseBackupCmd:
            cmdtag = "BASE_BACKUP";
            set_ps_display(cmdtag);
            PreventInTransactionBlock(true, cmdtag);
            SendBaseBackup((BaseBackupCmd *) cmd_node, uploaded_manifest);
            EndReplicationCommand(cmdtag);
            break;
 
        case T_CreateReplicationSlotCmd:
            cmdtag = "CREATE_REPLICATION_SLOT";
            set_ps_display(cmdtag);
            CreateReplicationSlot((CreateReplicationSlotCmd *) cmd_node);
            EndReplicationCommand(cmdtag);
            break;
 
        case T_DropReplicationSlotCmd:
            cmdtag = "DROP_REPLICATION_SLOT";
            set_ps_display(cmdtag);
            DropReplicationSlot((DropReplicationSlotCmd *) cmd_node);
            EndReplicationCommand(cmdtag);
            break;
 
        case T_AlterReplicationSlotCmd:
            cmdtag = "ALTER_REPLICATION_SLOT";
            set_ps_display(cmdtag);
            AlterReplicationSlot((AlterReplicationSlotCmd *) cmd_node);
            EndReplicationCommand(cmdtag);
            break;
 
        case T_StartReplicationCmd:
            {
                StartReplicationCmd *cmd = (StartReplicationCmd *) cmd_node;
 
                cmdtag = "START_REPLICATION";
                set_ps_display(cmdtag);
                PreventInTransactionBlock(true, cmdtag);
 
                if (cmd->kind == REPLICATION_KIND_PHYSICAL)
                    StartReplication(cmd);
                else
                    StartLogicalReplication(cmd);
 
                /* dupe, but necessary per libpqrcv_endstreaming */
                EndReplicationCommand(cmdtag);
 
                Assert(xlogreader != NULL);
                break;
            }
 
        case T_TimeLineHistoryCmd:
            cmdtag = "TIMELINE_HISTORY";
            set_ps_display(cmdtag);
            PreventInTransactionBlock(true, cmdtag);
            SendTimeLineHistory((TimeLineHistoryCmd *) cmd_node);
            EndReplicationCommand(cmdtag);
            break;
 
        case T_VariableShowStmt:
            {
                DestReceiver *dest = CreateDestReceiver(DestRemoteSimple);
                VariableShowStmt *n = (VariableShowStmt *) cmd_node;
 
                cmdtag = "SHOW";
                set_ps_display(cmdtag);
 
                /* syscache access needs a transaction environment */
                StartTransactionCommand();
                GetPGVariable(n->name, dest);
                CommitTransactionCommand();
                EndReplicationCommand(cmdtag);
            }
            break;
 
        case T_UploadManifestCmd:
            cmdtag = "UPLOAD_MANIFEST";
            set_ps_display(cmdtag);
            PreventInTransactionBlock(true, cmdtag);
            UploadManifest();
            EndReplicationCommand(cmdtag);
            break;
 
        default:
            elog(ERROR, "unrecognized replication command node tag: %u",
                 cmd_node->type);
    }
 
    /*
     * Done.  Revert to caller's memory context, and clean out the cmd_context
     * to recover memory right away.
     */
    MemoryContextSwitchTo(old_context);
    MemoryContextReset(cmd_context);
 
    /*
     * We need not update ps display or pg_stat_activity, because PostgresMain
     * will reset those to "idle".  But we must reset debug_query_string to
     * ensure it doesn't become a dangling pointer.
     */
    debug_query_string = NULL;
 
    return true;
}

References ALLOCSET_DEFAULT_SIZES, AllocSetContextCreate, AlterReplicationSlot(), Assert, CHECK_FOR_INTERRUPTS, CommitTransactionCommand(), CreateDestReceiver(), CreateReplicationSlot(), CurrentMemoryContext, DEBUG1, debug_query_string, DestRemoteSimple, DropReplicationSlot(), elog, EndReplicationCommand(), ereport, errcode(), errmsg, errmsg_internal(), ERROR, fb(), GetPGVariable(), got_STOPPING, IdentifySystem(), initStringInfo(), InvalidOid, IsAbortedTransactionBlockState(), StartReplicationCmd::kind, LOG, log_replication_commands, MemoryContextReset(), MemoryContextSwitchTo(), MyDatabaseId, MyWalSnd, VariableShowStmt::name, output_message, pgstat_report_activity(), PreventInTransactionBlock(), ReadReplicationSlot(), REPLICATION_KIND_PHYSICAL, replication_scanner_finish(), replication_scanner_init(), replication_scanner_is_replication_command(), replication_yyparse(), reply_message, SendBaseBackup(), SendTimeLineHistory(), set_ps_display(), SnapBuildClearExportedSnapshot(), StartLogicalReplication(), StartReplication(), StartTransactionCommand(), WalSnd::state, STATE_RUNNING, tmpbuf, TopMemoryContext, uploaded_manifest, UploadManifest(), WalSndSetState(), WALSNDSTATE_STOPPING, and xlogreader.

Referenced by PostgresMain().

GetStandbyFlushRecPtr()

XLogRecPtr GetStandbyFlushRecPtr

(

TimeLineID *

tli

)

Definition at line 3880 of file walsender.c.

{
    XLogRecPtr  replayPtr;
    TimeLineID  replayTLI;
    XLogRecPtr  receivePtr;
    TimeLineID  receiveTLI;
    XLogRecPtr  result;
 
    Assert(am_cascading_walsender || IsSyncingReplicationSlots());
 
    /*
     * We can safely send what's already been replayed. Also, if walreceiver
     * is streaming WAL from the same timeline, we can send anything that it
     * has streamed, but hasn't been replayed yet.
     */
 
    receivePtr = GetWalRcvFlushRecPtr(NULL, &receiveTLI);
    replayPtr = GetXLogReplayRecPtr(&replayTLI);
 
    if (tli)
        *tli = replayTLI;
 
    result = replayPtr;
    if (receiveTLI == replayTLI && receivePtr > replayPtr)
        result = receivePtr;
 
    return result;
}

References am_cascading_walsender, Assert, fb(), GetWalRcvFlushRecPtr(), GetXLogReplayRecPtr(), IsSyncingReplicationSlots(), receiveTLI, and result.

Referenced by IdentifySystem(), StartReplication(), update_local_synced_slot(), and XLogSendPhysical().

HandleUploadManifestPacket()

static bool HandleUploadManifestPacket ( StringInfo  buf, off_t *  offset, IncrementalBackupInfo *  ib  )

static

Definition at line 768 of file walsender.c.

{
    int         mtype;
    int         maxmsglen;
 
    HOLD_CANCEL_INTERRUPTS();
 
    pq_startmsgread();
    mtype = pq_getbyte();
    if (mtype == EOF)
        ereport(ERROR,
                (errcode(ERRCODE_CONNECTION_FAILURE),
                 errmsg("unexpected EOF on client connection with an open transaction")));
 
    switch (mtype)
    {
        case PqMsg_CopyData:
            maxmsglen = PQ_LARGE_MESSAGE_LIMIT;
            break;
        case PqMsg_CopyDone:
        case PqMsg_CopyFail:
        case PqMsg_Flush:
        case PqMsg_Sync:
            maxmsglen = PQ_SMALL_MESSAGE_LIMIT;
            break;
        default:
            ereport(ERROR,
                    (errcode(ERRCODE_PROTOCOL_VIOLATION),
                     errmsg("unexpected message type 0x%02X during COPY from stdin",
                            mtype)));
            maxmsglen = 0;      /* keep compiler quiet */
            break;
    }
 
    /* Now collect the message body */
    if (pq_getmessage(buf, maxmsglen))
        ereport(ERROR,
                (errcode(ERRCODE_CONNECTION_FAILURE),
                 errmsg("unexpected EOF on client connection with an open transaction")));
    RESUME_CANCEL_INTERRUPTS();
 
    /* Process the message */
    switch (mtype)
    {
        case PqMsg_CopyData:
            AppendIncrementalManifestData(ib, buf->data, buf->len);
            return true;
 
        case PqMsg_CopyDone:
            return false;
 
        case PqMsg_Sync:
        case PqMsg_Flush:
            /* Ignore these while in CopyOut mode as we do elsewhere. */
            return true;
 
        case PqMsg_CopyFail:
            ereport(ERROR,
                    (errcode(ERRCODE_QUERY_CANCELED),
                     errmsg("COPY from stdin failed: %s",
                            pq_getmsgstring(buf))));
    }
 
    /* Not reached. */
    Assert(false);
    return false;
}

References AppendIncrementalManifestData(), Assert, buf, ereport, errcode(), ERRCODE_PROTOCOL_VIOLATION, errmsg, ERROR, fb(), HOLD_CANCEL_INTERRUPTS, pq_getbyte(), pq_getmessage(), pq_getmsgstring(), PQ_LARGE_MESSAGE_LIMIT, PQ_SMALL_MESSAGE_LIMIT, pq_startmsgread(), PqMsg_CopyData, PqMsg_CopyDone, PqMsg_CopyFail, PqMsg_Flush, PqMsg_Sync, and RESUME_CANCEL_INTERRUPTS.

Referenced by UploadManifest().

HandleWalSndInitStopping()

void HandleWalSndInitStopping

(

void

)

Definition at line 3936 of file walsender.c.

{
    Assert(am_walsender);
 
    /*
     * If replication has not yet started, die like with SIGTERM. If
     * replication is active, only set a flag and wake up the main loop. It
     * will send any outstanding WAL, wait for it to be replicated to the
     * standby, and then exit gracefully.
     */
    if (!replication_active)
        kill(MyProcPid, SIGTERM);
    else
        got_STOPPING = true;
 
    /* latch will be set by procsignal_sigusr1_handler */
}

References am_walsender, Assert, fb(), got_STOPPING, kill, MyProcPid, and replication_active.

Referenced by procsignal_sigusr1_handler().

IdentifySystem()

static void IdentifySystem ( void  )

static

Definition at line 429 of file walsender.c.

{
    char        sysid[32];
    char        xloc[MAXFNAMELEN];
    XLogRecPtr  logptr;
    char       *dbname = NULL;
    DestReceiver *dest;
    TupOutputState *tstate;
    TupleDesc   tupdesc;
    Datum       values[4];
    bool        nulls[4] = {0};
    TimeLineID  currTLI;
 
    /*
     * Reply with a result set with one row, four columns. First col is system
     * ID, second is timeline ID, third is current xlog location and the
     * fourth contains the database name if we are connected to one.
     */
 
    snprintf(sysid, sizeof(sysid), UINT64_FORMAT,
             GetSystemIdentifier());
 
    am_cascading_walsender = RecoveryInProgress();
    if (am_cascading_walsender)
        logptr = GetStandbyFlushRecPtr(&currTLI);
    else
        logptr = GetFlushRecPtr(&currTLI);
 
    snprintf(xloc, sizeof(xloc), "%X/%08X", LSN_FORMAT_ARGS(logptr));
 
    if (MyDatabaseId != InvalidOid)
    {
        MemoryContext cur = CurrentMemoryContext;
 
        /* syscache access needs a transaction env. */
        StartTransactionCommand();
        dbname = get_database_name(MyDatabaseId);
        /* copy dbname out of TX context */
        dbname = MemoryContextStrdup(cur, dbname);
        CommitTransactionCommand();
    }
 
    dest = CreateDestReceiver(DestRemoteSimple);
 
    /* need a tuple descriptor representing four columns */
    tupdesc = CreateTemplateTupleDesc(4);
    TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 1, "systemid",
                              TEXTOID, -1, 0);
    TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 2, "timeline",
                              INT8OID, -1, 0);
    TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 3, "xlogpos",
                              TEXTOID, -1, 0);
    TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 4, "dbname",
                              TEXTOID, -1, 0);
    TupleDescFinalize(tupdesc);
 
    /* prepare for projection of tuples */
    tstate = begin_tup_output_tupdesc(dest, tupdesc, &TTSOpsVirtual);
 
    /* column 1: system identifier */
    values[0] = CStringGetTextDatum(sysid);
 
    /* column 2: timeline */
    values[1] = Int64GetDatum(currTLI);
 
    /* column 3: wal location */
    values[2] = CStringGetTextDatum(xloc);
 
    /* column 4: database name, or NULL if none */
    if (dbname)
        values[3] = CStringGetTextDatum(dbname);
    else
        nulls[3] = true;
 
    /* send it to dest */
    do_tup_output(tstate, values, nulls);
 
    end_tup_output(tstate);
}

References am_cascading_walsender, begin_tup_output_tupdesc(), CommitTransactionCommand(), CreateDestReceiver(), CreateTemplateTupleDesc(), CStringGetTextDatum, cur, CurrentMemoryContext, dbname, DestRemoteSimple, do_tup_output(), end_tup_output(), fb(), get_database_name(), GetFlushRecPtr(), GetStandbyFlushRecPtr(), GetSystemIdentifier(), Int64GetDatum(), InvalidOid, LSN_FORMAT_ARGS, MAXFNAMELEN, MemoryContextStrdup(), MyDatabaseId, RecoveryInProgress(), snprintf, StartTransactionCommand(), TTSOpsVirtual, TupleDescFinalize(), TupleDescInitBuiltinEntry(), UINT64_FORMAT, and values.

Referenced by exec_replication_command().

InitWalSender()

void InitWalSender

(

void

)

Definition at line 330 of file walsender.c.

{
    am_cascading_walsender = RecoveryInProgress();
 
    /* Create a per-walsender data structure in shared memory */
    InitWalSenderSlot();
 
    /* need resource owner for e.g. basebackups */
    CreateAuxProcessResourceOwner();
 
    /*
     * Let postmaster know that we're a WAL sender. Once we've declared us as
     * a WAL sender process, postmaster will let us outlive the bgwriter and
     * kill us last in the shutdown sequence, so we get a chance to stream all
     * remaining WAL at shutdown, including the shutdown checkpoint. Note that
     * there's no going back, and we mustn't write any WAL records after this.
     */
    MarkPostmasterChildWalSender();
    SendPostmasterSignal(PMSIGNAL_ADVANCE_STATE_MACHINE);
 
    /*
     * If the client didn't specify a database to connect to, show in PGPROC
     * that our advertised xmin should affect vacuum horizons in all
     * databases.  This allows physical replication clients to send hot
     * standby feedback that will delay vacuum cleanup in all databases.
     */
    if (MyDatabaseId == InvalidOid)
    {
        Assert(MyProc->xmin == InvalidTransactionId);
        LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
        MyProc->statusFlags |= PROC_AFFECTS_ALL_HORIZONS;
        ProcGlobal->statusFlags[MyProc->pgxactoff] = MyProc->statusFlags;
        LWLockRelease(ProcArrayLock);
    }
 
    /* Initialize empty timestamp buffer for lag tracking. */
    lag_tracker = MemoryContextAllocZero(TopMemoryContext, sizeof(LagTracker));
}

References am_cascading_walsender, Assert, CreateAuxProcessResourceOwner(), fb(), InitWalSenderSlot(), InvalidOid, InvalidTransactionId, lag_tracker, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), MarkPostmasterChildWalSender(), MemoryContextAllocZero(), MyDatabaseId, MyProc, PGPROC::pgxactoff, PMSIGNAL_ADVANCE_STATE_MACHINE, PROC_AFFECTS_ALL_HORIZONS, ProcGlobal, RecoveryInProgress(), SendPostmasterSignal(), PGPROC::statusFlags, PROC_HDR::statusFlags, TopMemoryContext, and PGPROC::xmin.

Referenced by PostgresMain().

InitWalSenderSlot()

static void InitWalSenderSlot ( void  )

static

Definition at line 3174 of file walsender.c.

{
    int         i;
 
    /*
     * WalSndCtl should be set up already (we inherit this by fork() or
     * EXEC_BACKEND mechanism from the postmaster).
     */
    Assert(WalSndCtl != NULL);
    Assert(MyWalSnd == NULL);
 
    /*
     * Find a free walsender slot and reserve it. This must not fail due to
     * the prior check for free WAL senders in InitProcess().
     */
    for (i = 0; i < max_wal_senders; i++)
    {
        WalSnd     *walsnd = &WalSndCtl->walsnds[i];
 
        SpinLockAcquire(&walsnd->mutex);
 
        if (walsnd->pid != 0)
        {
            SpinLockRelease(&walsnd->mutex);
            continue;
        }
        else
        {
            /*
             * Found a free slot. Reserve it for us.
             */
            walsnd->pid = MyProcPid;
            walsnd->state = WALSNDSTATE_STARTUP;
            walsnd->sentPtr = InvalidXLogRecPtr;
            walsnd->needreload = false;
            walsnd->write = InvalidXLogRecPtr;
            walsnd->flush = InvalidXLogRecPtr;
            walsnd->apply = InvalidXLogRecPtr;
            walsnd->writeLag = -1;
            walsnd->flushLag = -1;
            walsnd->applyLag = -1;
            walsnd->sync_standby_priority = 0;
            walsnd->replyTime = 0;
 
            /*
             * The kind assignment is done here and not in StartReplication()
             * and StartLogicalReplication(). Indeed, the logical walsender
             * needs to read WAL records (like snapshot of running
             * transactions) during the slot creation. So it needs to be woken
             * up based on its kind.
             *
             * The kind assignment could also be done in StartReplication(),
             * StartLogicalReplication() and CREATE_REPLICATION_SLOT but it
             * seems better to set it on one place.
             */
            if (MyDatabaseId == InvalidOid)
                walsnd->kind = REPLICATION_KIND_PHYSICAL;
            else
                walsnd->kind = REPLICATION_KIND_LOGICAL;
 
            SpinLockRelease(&walsnd->mutex);
            /* don't need the lock anymore */
            MyWalSnd = walsnd;
 
            break;
        }
    }
 
    Assert(MyWalSnd != NULL);
 
    /* Arrange to clean up at walsender exit */
    on_shmem_exit(WalSndKill, 0);
}

References Assert, fb(), i, InvalidOid, InvalidXLogRecPtr, max_wal_senders, MyDatabaseId, MyProcPid, MyWalSnd, on_shmem_exit(), REPLICATION_KIND_LOGICAL, REPLICATION_KIND_PHYSICAL, SpinLockAcquire(), SpinLockRelease(), WalSndCtl, WalSndKill(), WalSndCtlData::walsnds, and WALSNDSTATE_STARTUP.

Referenced by InitWalSender().

LagTrackerRead()

static TimeOffset LagTrackerRead ( int  head, XLogRecPtr  lsn, TimestampTz  now  )

static

Definition at line 4521 of file walsender.c.

{
    TimestampTz time = 0;
 
    /*
     * If 'lsn' has not passed the WAL position stored in the overflow entry,
     * return the elapsed time (in microseconds) since the saved local flush
     * time. If the flush time is in the future (due to clock drift), return
     * -1 to treat as no valid sample.
     *
     * Otherwise, switch back to using the buffer to control the read head and
     * compute the elapsed time.  The read head is then reset to point to the
     * oldest entry in the buffer.
     */
    if (lag_tracker->read_heads[head] == -1)
    {
        if (lag_tracker->overflowed[head].lsn > lsn)
            return (now >= lag_tracker->overflowed[head].time) ?
                now - lag_tracker->overflowed[head].time : -1;
 
        time = lag_tracker->overflowed[head].time;
        lag_tracker->last_read[head] = lag_tracker->overflowed[head];
        lag_tracker->read_heads[head] =
            (lag_tracker->write_head + 1) % LAG_TRACKER_BUFFER_SIZE;
    }
 
    /* Read all unread samples up to this LSN or end of buffer. */
    while (lag_tracker->read_heads[head] != lag_tracker->write_head &&
           lag_tracker->buffer[lag_tracker->read_heads[head]].lsn <= lsn)
    {
        time = lag_tracker->buffer[lag_tracker->read_heads[head]].time;
        lag_tracker->last_read[head] =
            lag_tracker->buffer[lag_tracker->read_heads[head]];
        lag_tracker->read_heads[head] =
            (lag_tracker->read_heads[head] + 1) % LAG_TRACKER_BUFFER_SIZE;
    }
 
    /*
     * If the lag tracker is empty, that means the standby has processed
     * everything we've ever sent so we should now clear 'last_read'.  If we
     * didn't do that, we'd risk using a stale and irrelevant sample for
     * interpolation at the beginning of the next burst of WAL after a period
     * of idleness.
     */
    if (lag_tracker->read_heads[head] == lag_tracker->write_head)
        lag_tracker->last_read[head].time = 0;
 
    if (time > now)
    {
        /* If the clock somehow went backwards, treat as not found. */
        return -1;
    }
    else if (time == 0)
    {
        /*
         * We didn't cross a time.  If there is a future sample that we
         * haven't reached yet, and we've already reached at least one sample,
         * let's interpolate the local flushed time.  This is mainly useful
         * for reporting a completely stuck apply position as having
         * increasing lag, since otherwise we'd have to wait for it to
         * eventually start moving again and cross one of our samples before
         * we can show the lag increasing.
         */
        if (lag_tracker->read_heads[head] == lag_tracker->write_head)
        {
            /* There are no future samples, so we can't interpolate. */
            return -1;
        }
        else if (lag_tracker->last_read[head].time != 0)
        {
            /* We can interpolate between last_read and the next sample. */
            double      fraction;
            WalTimeSample prev = lag_tracker->last_read[head];
            WalTimeSample next = lag_tracker->buffer[lag_tracker->read_heads[head]];
 
            if (lsn < prev.lsn)
            {
                /*
                 * Reported LSNs shouldn't normally go backwards, but it's
                 * possible when there is a timeline change.  Treat as not
                 * found.
                 */
                return -1;
            }
 
            Assert(prev.lsn < next.lsn);
 
            if (prev.time > next.time)
            {
                /* If the clock somehow went backwards, treat as not found. */
                return -1;
            }
 
            /* See how far we are between the previous and next samples. */
            fraction =
                (double) (lsn - prev.lsn) / (double) (next.lsn - prev.lsn);
 
            /* Scale the local flush time proportionally. */
            time = (TimestampTz)
                ((double) prev.time + (next.time - prev.time) * fraction);
        }
        else
        {
            /*
             * We have only a future sample, implying that we were entirely
             * caught up but and now there is a new burst of WAL and the
             * standby hasn't processed the first sample yet.  Until the
             * standby reaches the future sample the best we can do is report
             * the hypothetical lag if that sample were to be replayed now.
             */
            time = lag_tracker->buffer[lag_tracker->read_heads[head]].time;
        }
    }
 
    /* Return the elapsed time since local flush time in microseconds. */
    Assert(time != 0);
    return now - time;
}

References Assert, LagTracker::buffer, fb(), lag_tracker, LAG_TRACKER_BUFFER_SIZE, LagTracker::last_read, WalTimeSample::lsn, next, now(), LagTracker::overflowed, LagTracker::read_heads, WalTimeSample::time, and LagTracker::write_head.

Referenced by ProcessStandbyReplyMessage().

LagTrackerWrite()

static void LagTrackerWrite ( XLogRecPtr  lsn, TimestampTz  local_flush_time  )

static

Definition at line 4463 of file walsender.c.

{
    int         new_write_head;
    int         i;
 
    if (!am_walsender)
        return;
 
    /*
     * If the lsn hasn't advanced since last time, then do nothing.  This way
     * we only record a new sample when new WAL has been written.
     */
    if (lag_tracker->last_lsn == lsn)
        return;
    lag_tracker->last_lsn = lsn;
 
    /*
     * If advancing the write head of the circular buffer would crash into any
     * of the read heads, then the buffer is full.  In other words, the
     * slowest reader (presumably apply) is the one that controls the release
     * of space.
     */
    new_write_head = (lag_tracker->write_head + 1) % LAG_TRACKER_BUFFER_SIZE;
    for (i = 0; i < NUM_SYNC_REP_WAIT_MODE; ++i)
    {
        /*
         * If the buffer is full, move the slowest reader to a separate
         * overflow entry and free its space in the buffer so the write head
         * can advance.
         */
        if (new_write_head == lag_tracker->read_heads[i])
        {
            lag_tracker->overflowed[i] =
                lag_tracker->buffer[lag_tracker->read_heads[i]];
            lag_tracker->read_heads[i] = -1;
        }
    }
 
    /* Store a sample at the current write head position. */
    lag_tracker->buffer[lag_tracker->write_head].lsn = lsn;
    lag_tracker->buffer[lag_tracker->write_head].time = local_flush_time;
    lag_tracker->write_head = new_write_head;
}

References am_walsender, LagTracker::buffer, fb(), i, lag_tracker, LAG_TRACKER_BUFFER_SIZE, LagTracker::last_lsn, WalTimeSample::lsn, NUM_SYNC_REP_WAIT_MODE, LagTracker::overflowed, LagTracker::read_heads, WalTimeSample::time, and LagTracker::write_head.

Referenced by WalSndUpdateProgress(), and XLogSendPhysical().

logical_read_xlog_page()

static int logical_read_xlog_page ( XLogReaderState *  state, XLogRecPtr  targetPagePtr, int  reqLen, XLogRecPtr  targetRecPtr, char *  cur_page  )

static

Definition at line 1077 of file walsender.c.

{
    XLogRecPtr  flushptr;
    int         count;
    WALReadError errinfo;
    XLogSegNo   segno;
    TimeLineID  currTLI;
 
    /*
     * Make sure we have enough WAL available before retrieving the current
     * timeline.
     */
    flushptr = WalSndWaitForWal(targetPagePtr + reqLen);
 
    /* Fail if not enough (implies we are going to shut down) */
    if (flushptr < targetPagePtr + reqLen)
        return -1;
 
    /*
     * Since logical decoding is also permitted on a standby server, we need
     * to check if the server is in recovery to decide how to get the current
     * timeline ID (so that it also covers the promotion or timeline change
     * cases). We must determine am_cascading_walsender after waiting for the
     * required WAL so that it is correct when the walsender wakes up after a
     * promotion.
     */
    am_cascading_walsender = RecoveryInProgress();
 
    if (am_cascading_walsender)
    {
        TimeLineID  insertTLI;
 
        /*
         * If the insertion timeline has already been set, use it.
         * InsertTimeLineID is set before the WAL segments of the old timeline
         * are removed, before SharedRecoveryState switches to
         * RECOVERY_STATE_DONE.
         *
         * There is a window where RecoveryInProgress() still returns true but
         * the old timeline's WAL segments have already been removed or
         * recycled.  Using the WAL insertion timeline avoids attempting to
         * read from those removed segments, improving availability, and is a
         * safe thing to do as promotion copies the contents in the last
         * segment of the old timeline to the first segment of the new
         * timeline, up to the switchpoint.
         */
        insertTLI = GetWALInsertionTimeLineIfSet();
        if (insertTLI != 0)
            currTLI = insertTLI;
        else
            GetXLogReplayRecPtr(&currTLI);
    }
    else
        currTLI = GetWALInsertionTimeLine();
 
    XLogReadDetermineTimeline(state, targetPagePtr, reqLen, currTLI);
    sendTimeLineIsHistoric = (state->currTLI != currTLI);
    sendTimeLine = state->currTLI;
    sendTimeLineValidUpto = state->currTLIValidUntil;
    sendTimeLineNextTLI = state->nextTLI;
 
    if (targetPagePtr + XLOG_BLCKSZ <= flushptr)
        count = XLOG_BLCKSZ;    /* more than one block available */
    else
        count = flushptr - targetPagePtr;   /* part of the page available */
 
    /* now actually read the data, we know it's there */
    if (!WALRead(state,
                 cur_page,
                 targetPagePtr,
                 count,
                 currTLI,       /* Pass the current TLI because only
                                 * WalSndSegmentOpen controls whether new TLI
                                 * is needed. */
                 &errinfo))
        WALReadRaiseError(&errinfo);
 
    /*
     * After reading into the buffer, check that what we read was valid. We do
     * this after reading, because even though the segment was present when we
     * opened it, it might get recycled or removed while we read it. The
     * read() succeeds in that case, but the data we tried to read might
     * already have been overwritten with new WAL records.
     */
    XLByteToSeg(targetPagePtr, segno, state->segcxt.ws_segsize);
    CheckXLogRemoved(segno, state->seg.ws_tli);
 
    return count;
}

References am_cascading_walsender, CheckXLogRemoved(), fb(), GetWALInsertionTimeLine(), GetWALInsertionTimeLineIfSet(), GetXLogReplayRecPtr(), RecoveryInProgress(), sendTimeLine, sendTimeLineIsHistoric, sendTimeLineNextTLI, sendTimeLineValidUpto, WALRead(), WALReadRaiseError(), WalSndWaitForWal(), XLByteToSeg, and XLogReadDetermineTimeline().

Referenced by CreateReplicationSlot(), and StartLogicalReplication().

NeedToWaitForStandbys()

static bool NeedToWaitForStandbys ( XLogRecPtr  flushed_lsn, uint32 *  wait_event  )

static

Definition at line 1848 of file walsender.c.

{
    int         elevel = got_STOPPING ? ERROR : WARNING;
    bool        failover_slot;
 
    failover_slot = (replication_active && MyReplicationSlot->data.failover);
 
    /*
     * Note that after receiving the shutdown signal, an ERROR is reported if
     * any slots are dropped, invalidated, or inactive. This measure is taken
     * to prevent the walsender from waiting indefinitely.
     */
    if (failover_slot && !StandbySlotsHaveCaughtup(flushed_lsn, elevel))
    {
        *wait_event = WAIT_EVENT_WAIT_FOR_STANDBY_CONFIRMATION;
        return true;
    }
 
    *wait_event = 0;
    return false;
}

References ReplicationSlot::data, ERROR, ReplicationSlotPersistentData::failover, fb(), got_STOPPING, MyReplicationSlot, replication_active, StandbySlotsHaveCaughtup(), and WARNING.

Referenced by NeedToWaitForWal(), and WalSndWaitForWal().

NeedToWaitForWal()

static bool NeedToWaitForWal ( XLogRecPtr  target_lsn, XLogRecPtr  flushed_lsn, uint32 *  wait_event  )

static

Definition at line 1880 of file walsender.c.

{
    /* Check if we need to wait for WALs to be flushed to disk */
    if (target_lsn > flushed_lsn)
    {
        *wait_event = WAIT_EVENT_WAL_SENDER_WAIT_FOR_WAL;
        return true;
    }
 
    /* Check if the standby slots have caught up to the flushed position */
    return NeedToWaitForStandbys(flushed_lsn, wait_event);
}

References fb(), and NeedToWaitForStandbys().

Referenced by WalSndWaitForWal().

offset_to_interval()

static Interval * offset_to_interval ( TimeOffset  offset )

static

Definition at line 4215 of file walsender.c.

{
    Interval   *result = palloc_object(Interval);
 
    result->month = 0;
    result->day = 0;
    result->time = offset;
 
    return result;
}

References palloc_object, and result.

Referenced by pg_stat_get_wal_senders().

parseCreateReplSlotOptions()

static void parseCreateReplSlotOptions ( CreateReplicationSlotCmd *  cmd, bool *  reserve_wal, CRSSnapshotAction *  snapshot_action, bool *  two_phase, bool *  failover  )

static

Definition at line 1172 of file walsender.c.

{
    ListCell   *lc;
    bool        snapshot_action_given = false;
    bool        reserve_wal_given = false;
    bool        two_phase_given = false;
    bool        failover_given = false;
 
    /* Parse options */
    foreach(lc, cmd->options)
    {
        DefElem    *defel = (DefElem *) lfirst(lc);
 
        if (strcmp(defel->defname, "snapshot") == 0)
        {
            char       *action;
 
            if (snapshot_action_given || cmd->kind != REPLICATION_KIND_LOGICAL)
                ereport(ERROR,
                        (errcode(ERRCODE_SYNTAX_ERROR),
                         errmsg("conflicting or redundant options")));
 
            action = defGetString(defel);
            snapshot_action_given = true;
 
            if (strcmp(action, "export") == 0)
                *snapshot_action = CRS_EXPORT_SNAPSHOT;
            else if (strcmp(action, "nothing") == 0)
                *snapshot_action = CRS_NOEXPORT_SNAPSHOT;
            else if (strcmp(action, "use") == 0)
                *snapshot_action = CRS_USE_SNAPSHOT;
            else
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("unrecognized value for %s option \"%s\": \"%s\"",
                                "CREATE_REPLICATION_SLOT", defel->defname, action)));
        }
        else if (strcmp(defel->defname, "reserve_wal") == 0)
        {
            if (reserve_wal_given || cmd->kind != REPLICATION_KIND_PHYSICAL)
                ereport(ERROR,
                        (errcode(ERRCODE_SYNTAX_ERROR),
                         errmsg("conflicting or redundant options")));
 
            reserve_wal_given = true;
            *reserve_wal = defGetBoolean(defel);
        }
        else if (strcmp(defel->defname, "two_phase") == 0)
        {
            if (two_phase_given || cmd->kind != REPLICATION_KIND_LOGICAL)
                ereport(ERROR,
                        (errcode(ERRCODE_SYNTAX_ERROR),
                         errmsg("conflicting or redundant options")));
            two_phase_given = true;
            *two_phase = defGetBoolean(defel);
        }
        else if (strcmp(defel->defname, "failover") == 0)
        {
            if (failover_given || cmd->kind != REPLICATION_KIND_LOGICAL)
                ereport(ERROR,
                        (errcode(ERRCODE_SYNTAX_ERROR),
                         errmsg("conflicting or redundant options")));
            failover_given = true;
            *failover = defGetBoolean(defel);
        }
        else
            elog(ERROR, "unrecognized option: %s", defel->defname);
    }
}

References CRS_EXPORT_SNAPSHOT, CRS_NOEXPORT_SNAPSHOT, CRS_USE_SNAPSHOT, defGetBoolean(), defGetString(), elog, ereport, errcode(), errmsg, ERROR, failover, fb(), CreateReplicationSlotCmd::kind, lfirst, CreateReplicationSlotCmd::options, REPLICATION_KIND_LOGICAL, REPLICATION_KIND_PHYSICAL, and two_phase.

Referenced by CreateReplicationSlot().

pg_stat_get_wal_senders()

Datum pg_stat_get_wal_senders

(

PG_FUNCTION_ARGS

)

Definition at line 4231 of file walsender.c.

{
#define PG_STAT_GET_WAL_SENDERS_COLS    12
    ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
    SyncRepStandbyData *sync_standbys;
    int         num_standbys;
    int         i;
 
    InitMaterializedSRF(fcinfo, 0);
 
    /*
     * Get the currently active synchronous standbys.  This could be out of
     * date before we're done, but we'll use the data anyway.
     */
    num_standbys = SyncRepGetCandidateStandbys(&sync_standbys);
 
    for (i = 0; i < max_wal_senders; i++)
    {
        WalSnd     *walsnd = &WalSndCtl->walsnds[i];
        XLogRecPtr  sent_ptr;
        XLogRecPtr  write;
        XLogRecPtr  flush;
        XLogRecPtr  apply;
        TimeOffset  writeLag;
        TimeOffset  flushLag;
        TimeOffset  applyLag;
        int         priority;
        int         pid;
        WalSndState state;
        TimestampTz replyTime;
        bool        is_sync_standby;
        Datum       values[PG_STAT_GET_WAL_SENDERS_COLS];
        bool        nulls[PG_STAT_GET_WAL_SENDERS_COLS] = {0};
        int         j;
 
        /* Collect data from shared memory */
        SpinLockAcquire(&walsnd->mutex);
        if (walsnd->pid == 0)
        {
            SpinLockRelease(&walsnd->mutex);
            continue;
        }
        pid = walsnd->pid;
        sent_ptr = walsnd->sentPtr;
        state = walsnd->state;
        write = walsnd->write;
        flush = walsnd->flush;
        apply = walsnd->apply;
        writeLag = walsnd->writeLag;
        flushLag = walsnd->flushLag;
        applyLag = walsnd->applyLag;
        priority = walsnd->sync_standby_priority;
        replyTime = walsnd->replyTime;
        SpinLockRelease(&walsnd->mutex);
 
        /*
         * Detect whether walsender is/was considered synchronous.  We can
         * provide some protection against stale data by checking the PID
         * along with walsnd_index.
         */
        is_sync_standby = false;
        for (j = 0; j < num_standbys; j++)
        {
            if (sync_standbys[j].walsnd_index == i &&
                sync_standbys[j].pid == pid)
            {
                is_sync_standby = true;
                break;
            }
        }
 
        values[0] = Int32GetDatum(pid);
 
        if (!has_privs_of_role(GetUserId(), ROLE_PG_READ_ALL_STATS))
        {
            /*
             * Only superusers and roles with privileges of pg_read_all_stats
             * can see details. Other users only get the pid value to know
             * it's a walsender, but no details.
             */
            MemSet(&nulls[1], true, PG_STAT_GET_WAL_SENDERS_COLS - 1);
        }
        else
        {
            values[1] = CStringGetTextDatum(WalSndGetStateString(state));
 
            if (!XLogRecPtrIsValid(sent_ptr))
                nulls[2] = true;
            values[2] = LSNGetDatum(sent_ptr);
 
            if (!XLogRecPtrIsValid(write))
                nulls[3] = true;
            values[3] = LSNGetDatum(write);
 
            if (!XLogRecPtrIsValid(flush))
                nulls[4] = true;
            values[4] = LSNGetDatum(flush);
 
            if (!XLogRecPtrIsValid(apply))
                nulls[5] = true;
            values[5] = LSNGetDatum(apply);
 
            /*
             * Treat a standby such as a pg_basebackup background process
             * which always returns an invalid flush location, as an
             * asynchronous standby.
             */
            priority = XLogRecPtrIsValid(flush) ? priority : 0;
 
            if (writeLag < 0)
                nulls[6] = true;
            else
                values[6] = IntervalPGetDatum(offset_to_interval(writeLag));
 
            if (flushLag < 0)
                nulls[7] = true;
            else
                values[7] = IntervalPGetDatum(offset_to_interval(flushLag));
 
            if (applyLag < 0)
                nulls[8] = true;
            else
                values[8] = IntervalPGetDatum(offset_to_interval(applyLag));
 
            values[9] = Int32GetDatum(priority);
 
            /*
             * More easily understood version of standby state. This is purely
             * informational.
             *
             * In quorum-based sync replication, the role of each standby
             * listed in synchronous_standby_names can be changing very
             * frequently. Any standbys considered as "sync" at one moment can
             * be switched to "potential" ones at the next moment. So, it's
             * basically useless to report "sync" or "potential" as their sync
             * states. We report just "quorum" for them.
             */
            if (priority == 0)
                values[10] = CStringGetTextDatum("async");
            else if (is_sync_standby)
                values[10] = SyncRepConfig->syncrep_method == SYNC_REP_PRIORITY ?
                    CStringGetTextDatum("sync") : CStringGetTextDatum("quorum");
            else
                values[10] = CStringGetTextDatum("potential");
 
            if (replyTime == 0)
                nulls[11] = true;
            else
                values[11] = TimestampTzGetDatum(replyTime);
        }
 
        tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc,
                             values, nulls);
    }
 
    return (Datum) 0;
}

References CStringGetTextDatum, fb(), GetUserId(), has_privs_of_role(), i, InitMaterializedSRF(), Int32GetDatum(), IntervalPGetDatum(), j, LSNGetDatum(), max_wal_senders, MemSet, offset_to_interval(), PG_STAT_GET_WAL_SENDERS_COLS, SpinLockAcquire(), SpinLockRelease(), SYNC_REP_PRIORITY, SyncRepConfigData::syncrep_method, SyncRepConfig, SyncRepGetCandidateStandbys(), TimestampTzGetDatum(), tuplestore_putvalues(), values, WalSndCtl, WalSndGetStateString(), WalSndCtlData::walsnds, write, and XLogRecPtrIsValid.

PhysicalConfirmReceivedLocation()

static void PhysicalConfirmReceivedLocation ( XLogRecPtr  lsn )

static

Definition at line 2494 of file walsender.c.

{
    bool        changed = false;
    ReplicationSlot *slot = MyReplicationSlot;
 
    Assert(XLogRecPtrIsValid(lsn));
    SpinLockAcquire(&slot->mutex);
    if (slot->data.restart_lsn != lsn)
    {
        changed = true;
        slot->data.restart_lsn = lsn;
    }
    SpinLockRelease(&slot->mutex);
 
    if (changed)
    {
        ReplicationSlotMarkDirty();
        ReplicationSlotsComputeRequiredLSN();
        PhysicalWakeupLogicalWalSnd();
    }
 
    /*
     * One could argue that the slot should be saved to disk now, but that'd
     * be energy wasted - the worst thing lost information could cause here is
     * to give wrong information in a statistics view - we'll just potentially
     * be more conservative in removing files.
     */
}

References Assert, ReplicationSlot::data, fb(), ReplicationSlot::mutex, MyReplicationSlot, PhysicalWakeupLogicalWalSnd(), ReplicationSlotMarkDirty(), ReplicationSlotsComputeRequiredLSN(), ReplicationSlotPersistentData::restart_lsn, SpinLockAcquire(), SpinLockRelease(), and XLogRecPtrIsValid.

Referenced by ProcessStandbyReplyMessage().

PhysicalReplicationSlotNewXmin()

static void PhysicalReplicationSlotNewXmin ( TransactionId  feedbackXmin, TransactionId  feedbackCatalogXmin  )

static

Definition at line 2635 of file walsender.c.

{
    bool        changed = false;
    ReplicationSlot *slot = MyReplicationSlot;
 
    SpinLockAcquire(&slot->mutex);
    MyProc->xmin = InvalidTransactionId;
 
    /*
     * For physical replication we don't need the interlock provided by xmin
     * and effective_xmin since the consequences of a missed increase are
     * limited to query cancellations, so set both at once.
     */
    if (!TransactionIdIsNormal(slot->data.xmin) ||
        !TransactionIdIsNormal(feedbackXmin) ||
        TransactionIdPrecedes(slot->data.xmin, feedbackXmin))
    {
        changed = true;
        slot->data.xmin = feedbackXmin;
        slot->effective_xmin = feedbackXmin;
    }
    if (!TransactionIdIsNormal(slot->data.catalog_xmin) ||
        !TransactionIdIsNormal(feedbackCatalogXmin) ||
        TransactionIdPrecedes(slot->data.catalog_xmin, feedbackCatalogXmin))
    {
        changed = true;
        slot->data.catalog_xmin = feedbackCatalogXmin;
        slot->effective_catalog_xmin = feedbackCatalogXmin;
    }
    SpinLockRelease(&slot->mutex);
 
    if (changed)
    {
        ReplicationSlotMarkDirty();
        ReplicationSlotsComputeRequiredXmin(false);
    }
}

References ReplicationSlotPersistentData::catalog_xmin, ReplicationSlot::data, ReplicationSlot::effective_catalog_xmin, ReplicationSlot::effective_xmin, fb(), InvalidTransactionId, ReplicationSlot::mutex, MyProc, MyReplicationSlot, ReplicationSlotMarkDirty(), ReplicationSlotsComputeRequiredXmin(), SpinLockAcquire(), SpinLockRelease(), TransactionIdIsNormal, TransactionIdPrecedes(), ReplicationSlotPersistentData::xmin, and PGPROC::xmin.

Referenced by ProcessStandbyHSFeedbackMessage().

PhysicalWakeupLogicalWalSnd()

void PhysicalWakeupLogicalWalSnd

(

void

)

Definition at line 1823 of file walsender.c.

{
    Assert(MyReplicationSlot && SlotIsPhysical(MyReplicationSlot));
 
    /*
     * If we are running in a standby, there is no need to wake up walsenders.
     * This is because we do not support syncing slots to cascading standbys,
     * so, there are no walsenders waiting for standbys to catch up.
     */
    if (RecoveryInProgress())
        return;
 
    if (SlotExistsInSyncStandbySlots(NameStr(MyReplicationSlot->data.name)))
        ConditionVariableBroadcast(&WalSndCtl->wal_confirm_rcv_cv);
}

References Assert, ConditionVariableBroadcast(), ReplicationSlot::data, MyReplicationSlot, ReplicationSlotPersistentData::name, NameStr, RecoveryInProgress(), SlotExistsInSyncStandbySlots(), SlotIsPhysical, WalSndCtlData::wal_confirm_rcv_cv, and WalSndCtl.

Referenced by pg_physical_replication_slot_advance(), and PhysicalConfirmReceivedLocation().

ProcessPendingWrites()

static void ProcessPendingWrites ( void  )

static

Definition at line 1702 of file walsender.c.

{
    for (;;)
    {
        long        sleeptime;
 
        /* Check for input from the client */
        ProcessRepliesIfAny();
 
        /* die if timeout was reached */
        WalSndCheckTimeOut();
 
        /*
         * During shutdown, die if the shutdown timeout expires. Call this
         * before WalSndComputeSleeptime() so the timeout is considered when
         * computing sleep time.
         */
        WalSndCheckShutdownTimeout();
 
        /* Send keepalive if the time has come */
        WalSndKeepaliveIfNecessary();
 
        if (!pq_is_send_pending())
            break;
 
        sleeptime = WalSndComputeSleeptime(GetCurrentTimestamp());
 
        /* Sleep until something happens or we time out */
        WalSndWait(WL_SOCKET_WRITEABLE | WL_SOCKET_READABLE, sleeptime,
                   WAIT_EVENT_WAL_SENDER_WRITE_DATA);
 
        /* Clear any already-pending wakeups */
        ResetLatch(MyLatch);
 
        CHECK_FOR_INTERRUPTS();
 
        /* Process any requests or signals received recently */
        WalSndHandleConfigReload();
 
        /* Try to flush pending output to the client */
        if (pq_flush_if_writable() != 0)
            WalSndShutdown();
    }
 
    /* reactivate latch so WalSndLoop knows to continue */
    SetLatch(MyLatch);
}

References CHECK_FOR_INTERRUPTS, fb(), GetCurrentTimestamp(), MyLatch, pq_flush_if_writable, pq_is_send_pending, ProcessRepliesIfAny(), ResetLatch(), SetLatch(), WalSndCheckShutdownTimeout(), WalSndCheckTimeOut(), WalSndComputeSleeptime(), WalSndHandleConfigReload(), WalSndKeepaliveIfNecessary(), WalSndShutdown(), WalSndWait(), WL_SOCKET_READABLE, and WL_SOCKET_WRITEABLE.

Referenced by WalSndUpdateProgress(), and WalSndWriteData().

ProcessRepliesIfAny()

static void ProcessRepliesIfAny ( void  )

static

Definition at line 2343 of file walsender.c.

{
    unsigned char firstchar;
    int         maxmsglen;
    int         r;
    bool        received = false;
 
    last_processing = GetCurrentTimestamp();
 
    /*
     * If we already received a CopyDone from the frontend, any subsequent
     * message is the beginning of a new command, and should be processed in
     * the main processing loop.
     */
    while (!streamingDoneReceiving)
    {
        pq_startmsgread();
        r = pq_getbyte_if_available(&firstchar);
        if (r < 0)
        {
            /* unexpected error or EOF */
            ereport(COMMERROR,
                    (errcode(ERRCODE_PROTOCOL_VIOLATION),
                     errmsg("unexpected EOF on standby connection")));
            proc_exit(0);
        }
        if (r == 0)
        {
            /* no data available without blocking */
            pq_endmsgread();
            break;
        }
 
        /* Validate message type and set packet size limit */
        switch (firstchar)
        {
            case PqMsg_CopyData:
                maxmsglen = PQ_LARGE_MESSAGE_LIMIT;
                break;
            case PqMsg_CopyDone:
            case PqMsg_Terminate:
                maxmsglen = PQ_SMALL_MESSAGE_LIMIT;
                break;
            default:
                ereport(FATAL,
                        (errcode(ERRCODE_PROTOCOL_VIOLATION),
                         errmsg("invalid standby message type \"%c\"",
                                firstchar)));
                maxmsglen = 0;  /* keep compiler quiet */
                break;
        }
 
        /* Read the message contents */
        resetStringInfo(&reply_message);
        if (pq_getmessage(&reply_message, maxmsglen))
        {
            ereport(COMMERROR,
                    (errcode(ERRCODE_PROTOCOL_VIOLATION),
                     errmsg("unexpected EOF on standby connection")));
            proc_exit(0);
        }
 
        /* ... and process it */
        switch (firstchar)
        {
                /*
                 * PqMsg_CopyData means a standby reply wrapped in a CopyData
                 * packet.
                 */
            case PqMsg_CopyData:
                ProcessStandbyMessage();
                received = true;
                break;
 
                /*
                 * PqMsg_CopyDone means the standby requested to finish
                 * streaming.  Reply with CopyDone, if we had not sent that
                 * already.
                 */
            case PqMsg_CopyDone:
                if (!streamingDoneSending)
                {
                    pq_putmessage_noblock(PqMsg_CopyDone, NULL, 0);
                    streamingDoneSending = true;
                }
 
                streamingDoneReceiving = true;
                received = true;
                break;
 
                /*
                 * PqMsg_Terminate means that the standby is closing down the
                 * socket.
                 */
            case PqMsg_Terminate:
                proc_exit(0);
 
            default:
                Assert(false);  /* NOT REACHED */
        }
    }
 
    /*
     * Save the last reply timestamp if we've received at least one reply.
     */
    if (received)
    {
        last_reply_timestamp = last_processing;
        waiting_for_ping_response = false;
    }
}

References Assert, COMMERROR, ereport, errcode(), ERRCODE_PROTOCOL_VIOLATION, errmsg, FATAL, fb(), GetCurrentTimestamp(), last_processing, last_reply_timestamp, pq_endmsgread(), pq_getbyte_if_available(), pq_getmessage(), PQ_LARGE_MESSAGE_LIMIT, pq_putmessage_noblock, PQ_SMALL_MESSAGE_LIMIT, pq_startmsgread(), PqMsg_CopyData, PqMsg_CopyDone, PqMsg_Terminate, proc_exit(), ProcessStandbyMessage(), reply_message, resetStringInfo(), streamingDoneReceiving, streamingDoneSending, and waiting_for_ping_response.

Referenced by ProcessPendingWrites(), WalSndLoop(), and WalSndWaitForWal().

ProcessStandbyHSFeedbackMessage()

static void ProcessStandbyHSFeedbackMessage ( void  )

static

Definition at line 2715 of file walsender.c.

{
    TransactionId feedbackXmin;
    uint32      feedbackEpoch;
    TransactionId feedbackCatalogXmin;
    uint32      feedbackCatalogEpoch;
    TimestampTz replyTime;
 
    /*
     * Decipher the reply message. The caller already consumed the msgtype
     * byte. See XLogWalRcvSendHSFeedback() in walreceiver.c for the creation
     * of this message.
     */
    replyTime = pq_getmsgint64(&reply_message);
    feedbackXmin = pq_getmsgint(&reply_message, 4);
    feedbackEpoch = pq_getmsgint(&reply_message, 4);
    feedbackCatalogXmin = pq_getmsgint(&reply_message, 4);
    feedbackCatalogEpoch = pq_getmsgint(&reply_message, 4);
 
    if (message_level_is_interesting(DEBUG2))
    {
        char       *replyTimeStr;
 
        /* Copy because timestamptz_to_str returns a static buffer */
        replyTimeStr = pstrdup(timestamptz_to_str(replyTime));
 
        elog(DEBUG2, "hot standby feedback xmin %u epoch %u, catalog_xmin %u epoch %u reply_time %s",
             feedbackXmin,
             feedbackEpoch,
             feedbackCatalogXmin,
             feedbackCatalogEpoch,
             replyTimeStr);
 
        pfree(replyTimeStr);
    }
 
    /*
     * Update shared state for this WalSender process based on reply data from
     * standby.
     */
    {
        WalSnd     *walsnd = MyWalSnd;
 
        SpinLockAcquire(&walsnd->mutex);
        walsnd->replyTime = replyTime;
        SpinLockRelease(&walsnd->mutex);
    }
 
    /*
     * Unset WalSender's xmins if the feedback message values are invalid.
     * This happens when the downstream turned hot_standby_feedback off.
     */
    if (!TransactionIdIsNormal(feedbackXmin)
        && !TransactionIdIsNormal(feedbackCatalogXmin))
    {
        MyProc->xmin = InvalidTransactionId;
        if (MyReplicationSlot != NULL)
            PhysicalReplicationSlotNewXmin(feedbackXmin, feedbackCatalogXmin);
        return;
    }
 
    /*
     * Check that the provided xmin/epoch are sane, that is, not in the future
     * and not so far back as to be already wrapped around.  Ignore if not.
     */
    if (TransactionIdIsNormal(feedbackXmin) &&
        !TransactionIdInRecentPast(feedbackXmin, feedbackEpoch))
        return;
 
    if (TransactionIdIsNormal(feedbackCatalogXmin) &&
        !TransactionIdInRecentPast(feedbackCatalogXmin, feedbackCatalogEpoch))
        return;
 
    /*
     * Set the WalSender's xmin equal to the standby's requested xmin, so that
     * the xmin will be taken into account by GetSnapshotData() /
     * ComputeXidHorizons().  This will hold back the removal of dead rows and
     * thereby prevent the generation of cleanup conflicts on the standby
     * server.
     *
     * There is a small window for a race condition here: although we just
     * checked that feedbackXmin precedes nextXid, the nextXid could have
     * gotten advanced between our fetching it and applying the xmin below,
     * perhaps far enough to make feedbackXmin wrap around.  In that case the
     * xmin we set here would be "in the future" and have no effect.  No point
     * in worrying about this since it's too late to save the desired data
     * anyway.  Assuming that the standby sends us an increasing sequence of
     * xmins, this could only happen during the first reply cycle, else our
     * own xmin would prevent nextXid from advancing so far.
     *
     * We don't bother taking the ProcArrayLock here.  Setting the xmin field
     * is assumed atomic, and there's no real need to prevent concurrent
     * horizon determinations.  (If we're moving our xmin forward, this is
     * obviously safe, and if we're moving it backwards, well, the data is at
     * risk already since a VACUUM could already have determined the horizon.)
     *
     * If we're using a replication slot we reserve the xmin via that,
     * otherwise via the walsender's PGPROC entry. We can only track the
     * catalog xmin separately when using a slot, so we store the least of the
     * two provided when not using a slot.
     *
     * XXX: It might make sense to generalize the ephemeral slot concept and
     * always use the slot mechanism to handle the feedback xmin.
     */
    if (MyReplicationSlot != NULL)  /* XXX: persistency configurable? */
        PhysicalReplicationSlotNewXmin(feedbackXmin, feedbackCatalogXmin);
    else
    {
        if (TransactionIdIsNormal(feedbackCatalogXmin)
            && TransactionIdPrecedes(feedbackCatalogXmin, feedbackXmin))
            MyProc->xmin = feedbackCatalogXmin;
        else
            MyProc->xmin = feedbackXmin;
    }
}

References DEBUG2, elog, fb(), InvalidTransactionId, message_level_is_interesting(), MyProc, MyReplicationSlot, MyWalSnd, pfree(), PhysicalReplicationSlotNewXmin(), pq_getmsgint(), pq_getmsgint64(), pstrdup(), reply_message, SpinLockAcquire(), SpinLockRelease(), timestamptz_to_str(), TransactionIdInRecentPast(), TransactionIdIsNormal, TransactionIdPrecedes(), and PGPROC::xmin.

Referenced by ProcessStandbyMessage().

ProcessStandbyMessage()

static void ProcessStandbyMessage ( void  )

static

Definition at line 2459 of file walsender.c.

{
    char        msgtype;
 
    /*
     * Check message type from the first byte.
     */
    msgtype = pq_getmsgbyte(&reply_message);
 
    switch (msgtype)
    {
        case PqReplMsg_StandbyStatusUpdate:
            ProcessStandbyReplyMessage();
            break;
 
        case PqReplMsg_HotStandbyFeedback:
            ProcessStandbyHSFeedbackMessage();
            break;
 
        case PqReplMsg_PrimaryStatusRequest:
            ProcessStandbyPSRequestMessage();
            break;
 
        default:
            ereport(COMMERROR,
                    (errcode(ERRCODE_PROTOCOL_VIOLATION),
                     errmsg("unexpected message type \"%c\"", msgtype)));
            proc_exit(0);
    }
}

References COMMERROR, ereport, errcode(), ERRCODE_PROTOCOL_VIOLATION, errmsg, fb(), pq_getmsgbyte(), PqReplMsg_HotStandbyFeedback, PqReplMsg_PrimaryStatusRequest, PqReplMsg_StandbyStatusUpdate, proc_exit(), ProcessStandbyHSFeedbackMessage(), ProcessStandbyPSRequestMessage(), ProcessStandbyReplyMessage(), and reply_message.

Referenced by ProcessRepliesIfAny().

ProcessStandbyPSRequestMessage()

static void ProcessStandbyPSRequestMessage ( void  )

static

Definition at line 2835 of file walsender.c.

{
    XLogRecPtr  lsn = InvalidXLogRecPtr;
    TransactionId oldestXidInCommit;
    TransactionId oldestGXidInCommit;
    FullTransactionId nextFullXid;
    FullTransactionId fullOldestXidInCommit;
    WalSnd     *walsnd = MyWalSnd;
    TimestampTz replyTime;
 
    /*
     * This shouldn't happen because we don't support getting primary status
     * message from standby.
     */
    if (RecoveryInProgress())
        elog(ERROR, "the primary status is unavailable during recovery");
 
    replyTime = pq_getmsgint64(&reply_message);
 
    /*
     * Update shared state for this WalSender process based on reply data from
     * standby.
     */
    SpinLockAcquire(&walsnd->mutex);
    walsnd->replyTime = replyTime;
    SpinLockRelease(&walsnd->mutex);
 
    /*
     * Consider transactions in the current database, as only these are the
     * ones replicated.
     */
    oldestXidInCommit = GetOldestActiveTransactionId(true, false);
    oldestGXidInCommit = TwoPhaseGetOldestXidInCommit();
 
    /*
     * Update the oldest xid for standby transmission if an older prepared
     * transaction exists and is currently in commit phase.
     */
    if (TransactionIdIsValid(oldestGXidInCommit) &&
        TransactionIdPrecedes(oldestGXidInCommit, oldestXidInCommit))
        oldestXidInCommit = oldestGXidInCommit;
 
    nextFullXid = ReadNextFullTransactionId();
    fullOldestXidInCommit = FullTransactionIdFromAllowableAt(nextFullXid,
                                                             oldestXidInCommit);
    lsn = GetXLogWriteRecPtr();
 
    elog(DEBUG2, "sending primary status");
 
    /* construct the message... */
    resetStringInfo(&output_message);
    pq_sendbyte(&output_message, PqReplMsg_PrimaryStatusUpdate);
    pq_sendint64(&output_message, lsn);
    pq_sendint64(&output_message, (int64) U64FromFullTransactionId(fullOldestXidInCommit));
    pq_sendint64(&output_message, (int64) U64FromFullTransactionId(nextFullXid));
    pq_sendint64(&output_message, GetCurrentTimestamp());
 
    /* ... and send it wrapped in CopyData */
    pq_putmessage_noblock(PqMsg_CopyData, output_message.data, output_message.len);
}

References StringInfoData::data, DEBUG2, elog, ERROR, fb(), FullTransactionIdFromAllowableAt(), GetCurrentTimestamp(), GetOldestActiveTransactionId(), GetXLogWriteRecPtr(), InvalidXLogRecPtr, StringInfoData::len, MyWalSnd, output_message, pq_getmsgint64(), pq_putmessage_noblock, pq_sendbyte(), pq_sendint64(), PqMsg_CopyData, PqReplMsg_PrimaryStatusUpdate, ReadNextFullTransactionId(), RecoveryInProgress(), reply_message, resetStringInfo(), SpinLockAcquire(), SpinLockRelease(), TransactionIdIsValid, TransactionIdPrecedes(), TwoPhaseGetOldestXidInCommit(), and U64FromFullTransactionId.

Referenced by ProcessStandbyMessage().

ProcessStandbyReplyMessage()

static void ProcessStandbyReplyMessage ( void  )

static

Definition at line 2527 of file walsender.c.

{
    XLogRecPtr  writePtr,
                flushPtr,
                applyPtr;
    bool        replyRequested;
    TimeOffset  writeLag,
                flushLag,
                applyLag;
    bool        clearLagTimes;
    TimestampTz now;
    TimestampTz replyTime;
 
    static XLogRecPtr prevWritePtr = InvalidXLogRecPtr;
    static XLogRecPtr prevFlushPtr = InvalidXLogRecPtr;
    static XLogRecPtr prevApplyPtr = InvalidXLogRecPtr;
 
    /* the caller already consumed the msgtype byte */
    writePtr = pq_getmsgint64(&reply_message);
    flushPtr = pq_getmsgint64(&reply_message);
    applyPtr = pq_getmsgint64(&reply_message);
    replyTime = pq_getmsgint64(&reply_message);
    replyRequested = pq_getmsgbyte(&reply_message);
 
    if (message_level_is_interesting(DEBUG2))
    {
        char       *replyTimeStr;
 
        /* Copy because timestamptz_to_str returns a static buffer */
        replyTimeStr = pstrdup(timestamptz_to_str(replyTime));
 
        elog(DEBUG2, "write %X/%08X flush %X/%08X apply %X/%08X%s reply_time %s",
             LSN_FORMAT_ARGS(writePtr),
             LSN_FORMAT_ARGS(flushPtr),
             LSN_FORMAT_ARGS(applyPtr),
             replyRequested ? " (reply requested)" : "",
             replyTimeStr);
 
        pfree(replyTimeStr);
    }
 
    /* See if we can compute the round-trip lag for these positions. */
    now = GetCurrentTimestamp();
    writeLag = LagTrackerRead(SYNC_REP_WAIT_WRITE, writePtr, now);
    flushLag = LagTrackerRead(SYNC_REP_WAIT_FLUSH, flushPtr, now);
    applyLag = LagTrackerRead(SYNC_REP_WAIT_APPLY, applyPtr, now);
 
    /*
     * If the standby reports that it has fully replayed the WAL, and the
     * write/flush/apply positions remain unchanged across two consecutive
     * reply messages, forget the lag times measured when it last
     * wrote/flushed/applied a WAL record.
     *
     * The second message with unchanged positions typically results from
     * wal_receiver_status_interval expiring on the standby, so lag values are
     * usually cleared after that interval when there is no activity. This
     * avoids displaying stale lag data until more WAL traffic arrives.
     */
    clearLagTimes = (applyPtr == sentPtr && flushPtr == sentPtr &&
                     writePtr == prevWritePtr && flushPtr == prevFlushPtr &&
                     applyPtr == prevApplyPtr);
 
    prevWritePtr = writePtr;
    prevFlushPtr = flushPtr;
    prevApplyPtr = applyPtr;
 
    /* Send a reply if the standby requested one. */
    if (replyRequested)
        WalSndKeepalive(false, InvalidXLogRecPtr);
 
    /*
     * Update shared state for this WalSender process based on reply data from
     * standby.
     */
    {
        WalSnd     *walsnd = MyWalSnd;
 
        SpinLockAcquire(&walsnd->mutex);
        walsnd->write = writePtr;
        walsnd->flush = flushPtr;
        walsnd->apply = applyPtr;
        if (writeLag != -1 || clearLagTimes)
            walsnd->writeLag = writeLag;
        if (flushLag != -1 || clearLagTimes)
            walsnd->flushLag = flushLag;
        if (applyLag != -1 || clearLagTimes)
            walsnd->applyLag = applyLag;
        walsnd->replyTime = replyTime;
        SpinLockRelease(&walsnd->mutex);
    }
 
    if (!am_cascading_walsender)
        SyncRepReleaseWaiters();
 
    /*
     * Advance our local xmin horizon when the client confirmed a flush.
     */
    if (MyReplicationSlot && XLogRecPtrIsValid(flushPtr))
    {
        if (SlotIsLogical(MyReplicationSlot))
            LogicalConfirmReceivedLocation(flushPtr);
        else
            PhysicalConfirmReceivedLocation(flushPtr);
    }
}

References am_cascading_walsender, DEBUG2, elog, fb(), GetCurrentTimestamp(), InvalidXLogRecPtr, LagTrackerRead(), LogicalConfirmReceivedLocation(), LSN_FORMAT_ARGS, message_level_is_interesting(), MyReplicationSlot, MyWalSnd, now(), pfree(), PhysicalConfirmReceivedLocation(), pq_getmsgbyte(), pq_getmsgint64(), pstrdup(), reply_message, sentPtr, SlotIsLogical, SpinLockAcquire(), SpinLockRelease(), SYNC_REP_WAIT_APPLY, SYNC_REP_WAIT_FLUSH, SYNC_REP_WAIT_WRITE, SyncRepReleaseWaiters(), timestamptz_to_str(), WalSndKeepalive(), and XLogRecPtrIsValid.

Referenced by ProcessStandbyMessage().

ReadReplicationSlot()

static void ReadReplicationSlot ( ReadReplicationSlotCmd *  cmd )

static

Definition at line 511 of file walsender.c.

{
#define READ_REPLICATION_SLOT_COLS 3
    ReplicationSlot *slot;
    DestReceiver *dest;
    TupOutputState *tstate;
    TupleDesc   tupdesc;
    Datum       values[READ_REPLICATION_SLOT_COLS] = {0};
    bool        nulls[READ_REPLICATION_SLOT_COLS];
 
    tupdesc = CreateTemplateTupleDesc(READ_REPLICATION_SLOT_COLS);
    TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 1, "slot_type",
                              TEXTOID, -1, 0);
    TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 2, "restart_lsn",
                              TEXTOID, -1, 0);
    /* TimeLineID is unsigned, so int4 is not wide enough. */
    TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 3, "restart_tli",
                              INT8OID, -1, 0);
    TupleDescFinalize(tupdesc);
 
    memset(nulls, true, READ_REPLICATION_SLOT_COLS * sizeof(bool));
 
    LWLockAcquire(ReplicationSlotControlLock, LW_SHARED);
    slot = SearchNamedReplicationSlot(cmd->slotname, false);
    if (slot == NULL || !slot->in_use)
    {
        LWLockRelease(ReplicationSlotControlLock);
    }
    else
    {
        ReplicationSlot slot_contents;
        int         i = 0;
 
        /* Copy slot contents while holding spinlock */
        SpinLockAcquire(&slot->mutex);
        slot_contents = *slot;
        SpinLockRelease(&slot->mutex);
        LWLockRelease(ReplicationSlotControlLock);
 
        if (OidIsValid(slot_contents.data.database))
            ereport(ERROR,
                    errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                    errmsg("cannot use %s with a logical replication slot",
                           "READ_REPLICATION_SLOT"));
 
        /* slot type */
        values[i] = CStringGetTextDatum("physical");
        nulls[i] = false;
        i++;
 
        /* start LSN */
        if (XLogRecPtrIsValid(slot_contents.data.restart_lsn))
        {
            char        xloc[64];
 
            snprintf(xloc, sizeof(xloc), "%X/%08X",
                     LSN_FORMAT_ARGS(slot_contents.data.restart_lsn));
            values[i] = CStringGetTextDatum(xloc);
            nulls[i] = false;
        }
        i++;
 
        /* timeline this WAL was produced on */
        if (XLogRecPtrIsValid(slot_contents.data.restart_lsn))
        {
            TimeLineID  slots_position_timeline;
            TimeLineID  current_timeline;
            List       *timeline_history = NIL;
 
            /*
             * While in recovery, use as timeline the currently-replaying one
             * to get the LSN position's history.
             */
            if (RecoveryInProgress())
                (void) GetXLogReplayRecPtr(&current_timeline);
            else
                current_timeline = GetWALInsertionTimeLine();
 
            timeline_history = readTimeLineHistory(current_timeline);
            slots_position_timeline = tliOfPointInHistory(slot_contents.data.restart_lsn,
                                                          timeline_history);
            values[i] = Int64GetDatum((int64) slots_position_timeline);
            nulls[i] = false;
        }
        i++;
 
        Assert(i == READ_REPLICATION_SLOT_COLS);
    }
 
    dest = CreateDestReceiver(DestRemoteSimple);
    tstate = begin_tup_output_tupdesc(dest, tupdesc, &TTSOpsVirtual);
    do_tup_output(tstate, values, nulls);
    end_tup_output(tstate);
}

References Assert, begin_tup_output_tupdesc(), CreateDestReceiver(), CreateTemplateTupleDesc(), CStringGetTextDatum, DestRemoteSimple, do_tup_output(), end_tup_output(), ereport, errcode(), errmsg, ERROR, fb(), GetWALInsertionTimeLine(), GetXLogReplayRecPtr(), i, ReplicationSlot::in_use, Int64GetDatum(), LSN_FORMAT_ARGS, LW_SHARED, LWLockAcquire(), LWLockRelease(), ReplicationSlot::mutex, NIL, OidIsValid, READ_REPLICATION_SLOT_COLS, readTimeLineHistory(), RecoveryInProgress(), SearchNamedReplicationSlot(), ReadReplicationSlotCmd::slotname, snprintf, SpinLockAcquire(), SpinLockRelease(), tliOfPointInHistory(), TTSOpsVirtual, TupleDescFinalize(), TupleDescInitBuiltinEntry(), values, and XLogRecPtrIsValid.

Referenced by exec_replication_command().

SendTimeLineHistory()

static void SendTimeLineHistory ( TimeLineHistoryCmd *  cmd )

static

Definition at line 611 of file walsender.c.

{
    DestReceiver *dest;
    TupleDesc   tupdesc;
    StringInfoData buf;
    char        histfname[MAXFNAMELEN];
    char        path[MAXPGPATH];
    int         fd;
    off_t       histfilelen;
    off_t       bytesleft;
    Size        len;
 
    dest = CreateDestReceiver(DestRemoteSimple);
 
    /*
     * Reply with a result set with one row, and two columns. The first col is
     * the name of the history file, 2nd is the contents.
     */
    tupdesc = CreateTemplateTupleDesc(2);
    TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 1, "filename", TEXTOID, -1, 0);
    TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 2, "content", TEXTOID, -1, 0);
    TupleDescFinalize(tupdesc);
 
    TLHistoryFileName(histfname, cmd->timeline);
    TLHistoryFilePath(path, cmd->timeline);
 
    /* Send a RowDescription message */
    dest->rStartup(dest, CMD_SELECT, tupdesc);
 
    /* Send a DataRow message */
    pq_beginmessage(&buf, PqMsg_DataRow);
    pq_sendint16(&buf, 2);      /* # of columns */
    len = strlen(histfname);
    pq_sendint32(&buf, len);    /* col1 len */
    pq_sendbytes(&buf, histfname, len);
 
    fd = OpenTransientFile(path, O_RDONLY | PG_BINARY);
    if (fd < 0)
        ereport(ERROR,
                (errcode_for_file_access(),
                 errmsg("could not open file \"%s\": %m", path)));
 
    /* Determine file length and send it to client */
    histfilelen = lseek(fd, 0, SEEK_END);
    if (histfilelen < 0)
        ereport(ERROR,
                (errcode_for_file_access(),
                 errmsg("could not seek to end of file \"%s\": %m", path)));
    if (lseek(fd, 0, SEEK_SET) != 0)
        ereport(ERROR,
                (errcode_for_file_access(),
                 errmsg("could not seek to beginning of file \"%s\": %m", path)));
 
    pq_sendint32(&buf, histfilelen);    /* col2 len */
 
    bytesleft = histfilelen;
    while (bytesleft > 0)
    {
        PGAlignedBlock rbuf;
        int         nread;
 
        pgstat_report_wait_start(WAIT_EVENT_WALSENDER_TIMELINE_HISTORY_READ);
        nread = read(fd, rbuf.data, sizeof(rbuf));
        pgstat_report_wait_end();
        if (nread < 0)
            ereport(ERROR,
                    (errcode_for_file_access(),
                     errmsg("could not read file \"%s\": %m",
                            path)));
        else if (nread == 0)
            ereport(ERROR,
                    (errcode(ERRCODE_DATA_CORRUPTED),
                     errmsg("could not read file \"%s\": read %d of %zu",
                            path, nread, (Size) bytesleft)));
 
        pq_sendbytes(&buf, rbuf.data, nread);
        bytesleft -= nread;
    }
 
    if (CloseTransientFile(fd) != 0)
        ereport(ERROR,
                (errcode_for_file_access(),
                 errmsg("could not close file \"%s\": %m", path)));
 
    pq_endmessage(&buf);
}

References buf, CloseTransientFile(), CMD_SELECT, CreateDestReceiver(), CreateTemplateTupleDesc(), DestRemoteSimple, ereport, errcode(), ERRCODE_DATA_CORRUPTED, errcode_for_file_access(), errmsg, ERROR, fb(), fd(), len, MAXFNAMELEN, MAXPGPATH, OpenTransientFile(), PG_BINARY, pgstat_report_wait_end(), pgstat_report_wait_start(), pq_beginmessage(), pq_endmessage(), pq_sendbytes(), pq_sendint16(), pq_sendint32(), PqMsg_DataRow, read, TimeLineHistoryCmd::timeline, TLHistoryFileName(), TLHistoryFilePath(), TupleDescFinalize(), and TupleDescInitBuiltinEntry().

Referenced by exec_replication_command().

StartLogicalReplication()

static void StartLogicalReplication ( StartReplicationCmd *  cmd )

static

Definition at line 1514 of file walsender.c.

{
    StringInfoData buf;
    QueryCompletion qc;
 
    /* make sure that our requirements are still fulfilled */
    CheckLogicalDecodingRequirements(false);
 
    Assert(!MyReplicationSlot);
 
    ReplicationSlotAcquire(cmd->slotname, true, true);
 
    /*
     * Force a disconnect, so that the decoding code doesn't need to care
     * about an eventual switch from running in recovery, to running in a
     * normal environment. Client code is expected to handle reconnects.
     */
    if (am_cascading_walsender && !RecoveryInProgress())
    {
        ereport(LOG,
                (errmsg("terminating walsender process after promotion")));
        got_STOPPING = true;
    }
 
    /*
     * Create our decoding context, making it start at the previously ack'ed
     * position.
     *
     * Do this before sending a CopyBothResponse message, so that any errors
     * are reported early.
     */
    logical_decoding_ctx =
        CreateDecodingContext(cmd->startpoint, cmd->options, false,
                              XL_ROUTINE(.page_read = logical_read_xlog_page,
                                         .segment_open = WalSndSegmentOpen,
                                         .segment_close = wal_segment_close),
                              WalSndPrepareWrite, WalSndWriteData,
                              WalSndUpdateProgress);
    xlogreader = logical_decoding_ctx->reader;
 
    WalSndSetState(WALSNDSTATE_CATCHUP);
 
    /* Send a CopyBothResponse message, and start streaming */
    pq_beginmessage(&buf, PqMsg_CopyBothResponse);
    pq_sendbyte(&buf, 0);
    pq_sendint16(&buf, 0);
    pq_endmessage(&buf);
    pq_flush();
 
    /* Start reading WAL from the oldest required WAL. */
    XLogBeginRead(logical_decoding_ctx->reader,
                  MyReplicationSlot->data.restart_lsn);
 
    /*
     * Report the location after which we'll send out further commits as the
     * current sentPtr.
     */
    sentPtr = MyReplicationSlot->data.confirmed_flush;
 
    /* Also update the sent position status in shared memory */
    SpinLockAcquire(&MyWalSnd->mutex);
    MyWalSnd->sentPtr = MyReplicationSlot->data.restart_lsn;
    SpinLockRelease(&MyWalSnd->mutex);
 
    replication_active = true;
 
    SyncRepInitConfig();
 
    /* Main loop of walsender */
    WalSndLoop(XLogSendLogical);
 
    FreeDecodingContext(logical_decoding_ctx);
    ReplicationSlotRelease();
 
    replication_active = false;
    if (got_STOPPING)
        proc_exit(0);
    WalSndSetState(WALSNDSTATE_STARTUP);
 
    /* Get out of COPY mode (CommandComplete). */
    SetQueryCompletion(&qc, CMDTAG_COPY, 0);
    EndCommand(&qc, DestRemote, false);
}

References am_cascading_walsender, Assert, buf, CheckLogicalDecodingRequirements(), ReplicationSlotPersistentData::confirmed_flush, CreateDecodingContext(), ReplicationSlot::data, DestRemote, EndCommand(), ereport, errmsg, fb(), FreeDecodingContext(), got_STOPPING, LOG, logical_decoding_ctx, logical_read_xlog_page(), WalSnd::mutex, MyReplicationSlot, MyWalSnd, StartReplicationCmd::options, pq_beginmessage(), pq_endmessage(), pq_flush, pq_sendbyte(), pq_sendint16(), PqMsg_CopyBothResponse, proc_exit(), LogicalDecodingContext::reader, RecoveryInProgress(), replication_active, ReplicationSlotAcquire(), ReplicationSlotRelease(), ReplicationSlotPersistentData::restart_lsn, sentPtr, WalSnd::sentPtr, SetQueryCompletion(), StartReplicationCmd::slotname, SpinLockAcquire(), SpinLockRelease(), StartReplicationCmd::startpoint, SyncRepInitConfig(), wal_segment_close(), WalSndLoop(), WalSndPrepareWrite(), WalSndSegmentOpen(), WalSndSetState(), WALSNDSTATE_CATCHUP, WALSNDSTATE_STARTUP, WalSndUpdateProgress(), WalSndWriteData(), XL_ROUTINE, XLogBeginRead(), xlogreader, and XLogSendLogical().

Referenced by exec_replication_command().

StartReplication()

static void StartReplication ( StartReplicationCmd *  cmd )

static

Definition at line 844 of file walsender.c.

{
    StringInfoData buf;
    XLogRecPtr  FlushPtr;
    TimeLineID  FlushTLI;
 
    /* create xlogreader for physical replication */
    xlogreader =
        XLogReaderAllocate(wal_segment_size, NULL,
                           XL_ROUTINE(.segment_open = WalSndSegmentOpen,
                                      .segment_close = wal_segment_close),
                           NULL);
 
    if (!xlogreader)
        ereport(ERROR,
                (errcode(ERRCODE_OUT_OF_MEMORY),
                 errmsg("out of memory"),
                 errdetail("Failed while allocating a WAL reading processor.")));
 
    /*
     * We assume here that we're logging enough information in the WAL for
     * log-shipping, since this is checked in PostmasterMain().
     *
     * NOTE: wal_level can only change at shutdown, so in most cases it is
     * difficult for there to be WAL data that we can still see that was
     * written at wal_level='minimal'.
     */
 
    if (cmd->slotname)
    {
        ReplicationSlotAcquire(cmd->slotname, true, true);
        if (SlotIsLogical(MyReplicationSlot))
            ereport(ERROR,
                    (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                     errmsg("cannot use a logical replication slot for physical replication")));
 
        /*
         * We don't need to verify the slot's restart_lsn here; instead we
         * rely on the caller requesting the starting point to use.  If the
         * WAL segment doesn't exist, we'll fail later.
         */
    }
 
    /*
     * Select the timeline. If it was given explicitly by the client, use
     * that. Otherwise use the timeline of the last replayed record.
     */
    am_cascading_walsender = RecoveryInProgress();
    if (am_cascading_walsender)
        FlushPtr = GetStandbyFlushRecPtr(&FlushTLI);
    else
        FlushPtr = GetFlushRecPtr(&FlushTLI);
 
    if (cmd->timeline != 0)
    {
        XLogRecPtr  switchpoint;
 
        sendTimeLine = cmd->timeline;
        if (sendTimeLine == FlushTLI)
        {
            sendTimeLineIsHistoric = false;
            sendTimeLineValidUpto = InvalidXLogRecPtr;
        }
        else
        {
            List       *timeLineHistory;
 
            sendTimeLineIsHistoric = true;
 
            /*
             * Check that the timeline the client requested exists, and the
             * requested start location is on that timeline.
             */
            timeLineHistory = readTimeLineHistory(FlushTLI);
            switchpoint = tliSwitchPoint(cmd->timeline, timeLineHistory,
                                         &sendTimeLineNextTLI);
            list_free_deep(timeLineHistory);
 
            /*
             * Found the requested timeline in the history. Check that
             * requested startpoint is on that timeline in our history.
             *
             * This is quite loose on purpose. We only check that we didn't
             * fork off the requested timeline before the switchpoint. We
             * don't check that we switched *to* it before the requested
             * starting point. This is because the client can legitimately
             * request to start replication from the beginning of the WAL
             * segment that contains switchpoint, but on the new timeline, so
             * that it doesn't end up with a partial segment. If you ask for
             * too old a starting point, you'll get an error later when we
             * fail to find the requested WAL segment in pg_wal.
             *
             * XXX: we could be more strict here and only allow a startpoint
             * that's older than the switchpoint, if it's still in the same
             * WAL segment.
             */
            if (XLogRecPtrIsValid(switchpoint) &&
                switchpoint < cmd->startpoint)
            {
                ereport(ERROR,
                        errmsg("requested starting point %X/%08X on timeline %u is not in this server's history",
                               LSN_FORMAT_ARGS(cmd->startpoint),
                               cmd->timeline),
                        errdetail("This server's history forked from timeline %u at %X/%08X.",
                                  cmd->timeline,
                                  LSN_FORMAT_ARGS(switchpoint)));
            }
            sendTimeLineValidUpto = switchpoint;
        }
    }
    else
    {
        sendTimeLine = FlushTLI;
        sendTimeLineValidUpto = InvalidXLogRecPtr;
        sendTimeLineIsHistoric = false;
    }
 
    streamingDoneSending = streamingDoneReceiving = false;
 
    /* If there is nothing to stream, don't even enter COPY mode */
    if (!sendTimeLineIsHistoric || cmd->startpoint < sendTimeLineValidUpto)
    {
        /*
         * When we first start replication the standby will be behind the
         * primary. For some applications, for example synchronous
         * replication, it is important to have a clear state for this initial
         * catchup mode, so we can trigger actions when we change streaming
         * state later. We may stay in this state for a long time, which is
         * exactly why we want to be able to monitor whether or not we are
         * still here.
         */
        WalSndSetState(WALSNDSTATE_CATCHUP);
 
        /* Send a CopyBothResponse message, and start streaming */
        pq_beginmessage(&buf, PqMsg_CopyBothResponse);
        pq_sendbyte(&buf, 0);
        pq_sendint16(&buf, 0);
        pq_endmessage(&buf);
        pq_flush();
 
        /*
         * Don't allow a request to stream from a future point in WAL that
         * hasn't been flushed to disk in this server yet.
         */
        if (FlushPtr < cmd->startpoint)
        {
            ereport(ERROR,
                    errmsg("requested starting point %X/%08X is ahead of the WAL flush position of this server %X/%08X",
                           LSN_FORMAT_ARGS(cmd->startpoint),
                           LSN_FORMAT_ARGS(FlushPtr)));
        }
 
        /* Start streaming from the requested point */
        sentPtr = cmd->startpoint;
 
        /* Initialize shared memory status, too */
        SpinLockAcquire(&MyWalSnd->mutex);
        MyWalSnd->sentPtr = sentPtr;
        SpinLockRelease(&MyWalSnd->mutex);
 
        SyncRepInitConfig();
 
        /* Main loop of walsender */
        replication_active = true;
 
        WalSndLoop(XLogSendPhysical);
 
        replication_active = false;
        if (got_STOPPING)
            proc_exit(0);
        WalSndSetState(WALSNDSTATE_STARTUP);
 
        Assert(streamingDoneSending && streamingDoneReceiving);
    }
 
    if (cmd->slotname)
        ReplicationSlotRelease();
 
    /*
     * Copy is finished now. Send a single-row result set indicating the next
     * timeline.
     */
    if (sendTimeLineIsHistoric)
    {
        char        startpos_str[8 + 1 + 8 + 1];
        DestReceiver *dest;
        TupOutputState *tstate;
        TupleDesc   tupdesc;
        Datum       values[2];
        bool        nulls[2] = {0};
 
        snprintf(startpos_str, sizeof(startpos_str), "%X/%08X",
                 LSN_FORMAT_ARGS(sendTimeLineValidUpto));
 
        dest = CreateDestReceiver(DestRemoteSimple);
 
        /*
         * Need a tuple descriptor representing two columns. int8 may seem
         * like a surprising data type for this, but in theory int4 would not
         * be wide enough for this, as TimeLineID is unsigned.
         */
        tupdesc = CreateTemplateTupleDesc(2);
        TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 1, "next_tli",
                                  INT8OID, -1, 0);
        TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 2, "next_tli_startpos",
                                  TEXTOID, -1, 0);
        TupleDescFinalize(tupdesc);
 
        /* prepare for projection of tuple */
        tstate = begin_tup_output_tupdesc(dest, tupdesc, &TTSOpsVirtual);
 
        values[0] = Int64GetDatum((int64) sendTimeLineNextTLI);
        values[1] = CStringGetTextDatum(startpos_str);
 
        /* send it to dest */
        do_tup_output(tstate, values, nulls);
 
        end_tup_output(tstate);
    }
 
    /* Send CommandComplete message */
    EndReplicationCommand("START_STREAMING");
}

References am_cascading_walsender, Assert, begin_tup_output_tupdesc(), buf, CreateDestReceiver(), CreateTemplateTupleDesc(), CStringGetTextDatum, DestRemoteSimple, do_tup_output(), end_tup_output(), EndReplicationCommand(), ereport, errcode(), errdetail(), errmsg, ERROR, fb(), GetFlushRecPtr(), GetStandbyFlushRecPtr(), got_STOPPING, Int64GetDatum(), InvalidXLogRecPtr, list_free_deep(), LSN_FORMAT_ARGS, WalSnd::mutex, MyReplicationSlot, MyWalSnd, pq_beginmessage(), pq_endmessage(), pq_flush, pq_sendbyte(), pq_sendint16(), PqMsg_CopyBothResponse, proc_exit(), readTimeLineHistory(), RecoveryInProgress(), replication_active, ReplicationSlotAcquire(), ReplicationSlotRelease(), sendTimeLine, sendTimeLineIsHistoric, sendTimeLineNextTLI, sendTimeLineValidUpto, sentPtr, WalSnd::sentPtr, SlotIsLogical, StartReplicationCmd::slotname, snprintf, SpinLockAcquire(), SpinLockRelease(), StartReplicationCmd::startpoint, streamingDoneReceiving, streamingDoneSending, SyncRepInitConfig(), StartReplicationCmd::timeline, tliSwitchPoint(), TTSOpsVirtual, TupleDescFinalize(), TupleDescInitBuiltinEntry(), values, wal_segment_close(), wal_segment_size, WalSndLoop(), WalSndSegmentOpen(), WalSndSetState(), WALSNDSTATE_CATCHUP, WALSNDSTATE_STARTUP, XL_ROUTINE, xlogreader, XLogReaderAllocate(), XLogRecPtrIsValid, and XLogSendPhysical().

Referenced by exec_replication_command().

TransactionIdInRecentPast()

static bool TransactionIdInRecentPast ( TransactionId  xid, uint32  epoch  )

static

Definition at line 2684 of file walsender.c.

{
    FullTransactionId nextFullXid;
    TransactionId nextXid;
    uint32      nextEpoch;
 
    nextFullXid = ReadNextFullTransactionId();
    nextXid = XidFromFullTransactionId(nextFullXid);
    nextEpoch = EpochFromFullTransactionId(nextFullXid);
 
    if (xid <= nextXid)
    {
        if (epoch != nextEpoch)
            return false;
    }
    else
    {
        if (epoch + 1 != nextEpoch)
            return false;
    }
 
    if (!TransactionIdPrecedesOrEquals(xid, nextXid))
        return false;           /* epoch OK, but it's wrapped around */
 
    return true;
}

References epoch, EpochFromFullTransactionId, fb(), ReadNextFullTransactionId(), TransactionIdPrecedesOrEquals(), and XidFromFullTransactionId.

Referenced by ProcessStandbyHSFeedbackMessage().

UploadManifest()

static void UploadManifest ( void  )

static

Definition at line 702 of file walsender.c.

{
    MemoryContext mcxt;
    IncrementalBackupInfo *ib;
    off_t       offset = 0;
    StringInfoData buf;
 
    /*
     * parsing the manifest will use the cryptohash stuff, which requires a
     * resource owner
     */
    Assert(AuxProcessResourceOwner != NULL);
    Assert(CurrentResourceOwner == AuxProcessResourceOwner ||
           CurrentResourceOwner == NULL);
    CurrentResourceOwner = AuxProcessResourceOwner;
 
    /* Prepare to read manifest data into a temporary context. */
    mcxt = AllocSetContextCreate(CurrentMemoryContext,
                                 "incremental backup information",
                                 ALLOCSET_DEFAULT_SIZES);
    ib = CreateIncrementalBackupInfo(mcxt);
 
    /* Send a CopyInResponse message */
    pq_beginmessage(&buf, PqMsg_CopyInResponse);
    pq_sendbyte(&buf, 0);
    pq_sendint16(&buf, 0);
    pq_endmessage_reuse(&buf);
    pq_flush();
 
    /* Receive packets from client until done. */
    while (HandleUploadManifestPacket(&buf, &offset, ib))
        ;
 
    /* Finish up manifest processing. */
    FinalizeIncrementalManifest(ib);
 
    /*
     * Discard any old manifest information and arrange to preserve the new
     * information we just got.
     *
     * We assume that MemoryContextDelete and MemoryContextSetParent won't
     * fail, and thus we shouldn't end up bailing out of here in such a way as
     * to leave dangling pointers.
     */
    if (uploaded_manifest_mcxt != NULL)
        MemoryContextDelete(uploaded_manifest_mcxt);
    MemoryContextSetParent(mcxt, CacheMemoryContext);
    uploaded_manifest = ib;
    uploaded_manifest_mcxt = mcxt;
 
    /* clean up the resource owner we created */
    ReleaseAuxProcessResources(true);
}

References ALLOCSET_DEFAULT_SIZES, AllocSetContextCreate, Assert, AuxProcessResourceOwner, buf, CacheMemoryContext, CreateIncrementalBackupInfo(), CurrentMemoryContext, CurrentResourceOwner, fb(), FinalizeIncrementalManifest(), HandleUploadManifestPacket(), MemoryContextDelete(), MemoryContextSetParent(), pq_beginmessage(), pq_endmessage_reuse(), pq_flush, pq_sendbyte(), pq_sendint16(), PqMsg_CopyInResponse, ReleaseAuxProcessResources(), uploaded_manifest, and uploaded_manifest_mcxt.

Referenced by exec_replication_command().

WalSndCheckShutdownTimeout()

static void WalSndCheckShutdownTimeout ( void  )

static

Definition at line 2994 of file walsender.c.

{
    TimestampTz now;
 
    /* Do nothing if shutdown has not been requested yet */
    if (!(got_STOPPING || got_SIGUSR2))
        return;
 
    /* Terminate immediately if the timeout is set to 0 */
    if (wal_sender_shutdown_timeout == 0)
        WalSndDoneImmediate();
 
    /*
     * Record the shutdown request timestamp even if
     * wal_sender_shutdown_timeout is disabled (-1), since the setting may
     * change during shutdown and the timestamp will be needed in that case.
     */
    if (shutdown_request_timestamp == 0)
    {
        shutdown_request_timestamp = GetCurrentTimestamp();
        return;
    }
 
    /* Do not check the timeout if it's disabled */
    if (wal_sender_shutdown_timeout == -1)
        return;
 
    /* Terminate immediately if the timeout expires */
    now = GetCurrentTimestamp();
    if (TimestampDifferenceExceeds(shutdown_request_timestamp, now,
                                   wal_sender_shutdown_timeout))
        WalSndDoneImmediate();
}

References GetCurrentTimestamp(), got_SIGUSR2, got_STOPPING, now(), shutdown_request_timestamp, TimestampDifferenceExceeds(), wal_sender_shutdown_timeout, and WalSndDoneImmediate().

Referenced by ProcessPendingWrites(), WalSndDone(), WalSndLoop(), and WalSndWaitForWal().

WalSndCheckTimeOut()

static void WalSndCheckTimeOut ( void  )

static

Definition at line 2964 of file walsender.c.

{
    TimestampTz timeout;
 
    /* don't bail out if we're doing something that doesn't require timeouts */
    if (last_reply_timestamp <= 0)
        return;
 
    timeout = TimestampTzPlusMilliseconds(last_reply_timestamp,
                                          wal_sender_timeout);
 
    if (wal_sender_timeout > 0 && last_processing >= timeout)
    {
        /*
         * Since typically expiration of replication timeout means
         * communication problem, we don't send the error message to the
         * standby.
         */
        ereport(COMMERROR,
                (errmsg("terminating walsender process due to replication timeout")));
 
        WalSndShutdown();
    }
}

References COMMERROR, ereport, errmsg, fb(), last_processing, last_reply_timestamp, TimestampTzPlusMilliseconds, wal_sender_timeout, and WalSndShutdown().

Referenced by ProcessPendingWrites(), WalSndLoop(), and WalSndWaitForWal().

WalSndComputeSleeptime()

static long WalSndComputeSleeptime ( TimestampTz  now )

static

Definition at line 2907 of file walsender.c.

{
    TimestampTz wakeup_time;
    long        sleeptime = 10000;  /* 10 s */
 
    if (wal_sender_timeout > 0 && last_reply_timestamp > 0)
    {
        /*
         * At the latest stop sleeping once wal_sender_timeout has been
         * reached.
         */
        wakeup_time = TimestampTzPlusMilliseconds(last_reply_timestamp,
                                                  wal_sender_timeout);
 
        /*
         * If no ping has been sent yet, wakeup when it's time to do so.
         * WalSndKeepaliveIfNecessary() wants to send a keepalive once half of
         * the timeout passed without a response.
         */
        if (!waiting_for_ping_response)
            wakeup_time = TimestampTzPlusMilliseconds(last_reply_timestamp,
                                                      wal_sender_timeout / 2);
 
        /* Compute relative time until wakeup. */
        sleeptime = TimestampDifferenceMilliseconds(now, wakeup_time);
    }
 
    if (shutdown_request_timestamp != 0 && wal_sender_shutdown_timeout > 0)
    {
        long        shutdown_sleeptime;
 
        wakeup_time = TimestampTzPlusMilliseconds(shutdown_request_timestamp,
                                                  wal_sender_shutdown_timeout);
 
        shutdown_sleeptime = TimestampDifferenceMilliseconds(now, wakeup_time);
 
        /* Choose the earliest wakeup. */
        if (shutdown_sleeptime < sleeptime)
            sleeptime = shutdown_sleeptime;
    }
 
    return sleeptime;
}

References fb(), last_reply_timestamp, now(), shutdown_request_timestamp, TimestampDifferenceMilliseconds(), TimestampTzPlusMilliseconds, waiting_for_ping_response, wal_sender_shutdown_timeout, and wal_sender_timeout.

Referenced by ProcessPendingWrites(), WalSndDone(), WalSndLoop(), and WalSndWaitForWal().

WalSndDone()

static void WalSndDone ( WalSndSendDataCallback  send_data )

static

Definition at line 3792 of file walsender.c.

{
    XLogRecPtr  replicatedPtr;
 
    /* ... let's just be real sure we're caught up ... */
    send_data();
 
    /*
     * To figure out whether all WAL has successfully been replicated, check
     * flush location if valid, write otherwise. Tools like pg_receivewal will
     * usually (unless in synchronous mode) return an invalid flush location.
     */
    replicatedPtr = XLogRecPtrIsValid(MyWalSnd->flush) ?
        MyWalSnd->flush : MyWalSnd->write;
 
    if (WalSndCaughtUp && sentPtr == replicatedPtr &&
        !pq_is_send_pending())
    {
        QueryCompletion qc;
 
        Assert(!shutdown_stream_done_queued);
 
        /* Inform the standby that XLOG streaming is done */
        SetQueryCompletion(&qc, CMDTAG_COPY, 0);
        EndCommandExtended(&qc, DestRemote, false, true);
        shutdown_stream_done_queued = true;
 
        /*
         * Reset last_reply_timestamp so subsequent WalSndComputeSleeptime()
         * calls ignore wal_sender_timeout during shutdown.
         */
        last_reply_timestamp = 0;
 
        /*
         * Do not call pq_flush() here, since it can block indefinitely while
         * waiting for the socket to become writable, preventing
         * wal_sender_shutdown_timeout from being enforced. Instead, use the
         * walsender nonblocking flush path so the shutdown timeout continues
         * to be checked while the send buffer drains.
         */
        for (;;)
        {
            long        sleeptime;
 
            /*
             * During shutdown, die if the shutdown timeout expires. Call this
             * before WalSndComputeSleeptime() so the timeout is considered
             * when computing sleep time.
             */
            WalSndCheckShutdownTimeout();
 
            if (!pq_is_send_pending())
                break;
 
            sleeptime = WalSndComputeSleeptime(GetCurrentTimestamp());
 
            /* Sleep until something happens or we time out */
            WalSndWait(WL_SOCKET_WRITEABLE, sleeptime,
                       WAIT_EVENT_WAL_SENDER_WRITE_DATA);
 
            /* Clear any already-pending wakeups */
            ResetLatch(MyLatch);
 
            CHECK_FOR_INTERRUPTS();
 
            /* Try to flush pending output to the client */
            if (pq_flush_if_writable() != 0)
                WalSndShutdown();
        }
 
        proc_exit(0);
    }
    if (!waiting_for_ping_response)
        WalSndKeepalive(true, InvalidXLogRecPtr);
}

References Assert, CHECK_FOR_INTERRUPTS, DestRemote, EndCommandExtended(), fb(), WalSnd::flush, GetCurrentTimestamp(), InvalidXLogRecPtr, last_reply_timestamp, MyLatch, MyWalSnd, pq_flush_if_writable, pq_is_send_pending, proc_exit(), ResetLatch(), sentPtr, SetQueryCompletion(), shutdown_stream_done_queued, waiting_for_ping_response, WalSndCaughtUp, WalSndCheckShutdownTimeout(), WalSndComputeSleeptime(), WalSndKeepalive(), WalSndShutdown(), WalSndWait(), WL_SOCKET_WRITEABLE, WalSnd::write, and XLogRecPtrIsValid.

Referenced by WalSndLoop().

WalSndDoneImmediate()

static void WalSndDoneImmediate ( void  )

static

Definition at line 3741 of file walsender.c.

{
    WalSndState state = MyWalSnd->state;
 
    if ((state == WALSNDSTATE_CATCHUP ||
         state == WALSNDSTATE_STREAMING ||
         state == WALSNDSTATE_STOPPING) &&
        !shutdown_stream_done_queued)
    {
        QueryCompletion qc;
 
        /* Try to inform receiver that XLOG streaming is done */
        SetQueryCompletion(&qc, CMDTAG_COPY, 0);
        EndCommandExtended(&qc, DestRemote, false, true);
        shutdown_stream_done_queued = true;
 
        /*
         * Note that the output buffer may be full during the forced shutdown
         * of walsender. If pq_flush() is called at that time, the walsender
         * process will be stuck. Therefore, call pq_flush_if_writable()
         * instead. Successful reception of the done message with the
         * walsender forced into a shutdown is not guaranteed.
         */
        pq_flush_if_writable();
    }
 
    /*
     * Prevent ereport from attempting to send any more messages to the
     * standby. Otherwise, it can cause the process to get stuck if the output
     * buffers are full.
     */
    if (whereToSendOutput == DestRemote)
        whereToSendOutput = DestNone;
 
    ereport(WARNING,
            (errmsg("terminating walsender process due to replication shutdown timeout"),
             errdetail("Walsender process might have been terminated before all WAL data was replicated to the receiver.")));
 
    proc_exit(0);
}

References DestNone, DestRemote, EndCommandExtended(), ereport, errdetail(), errmsg, fb(), MyWalSnd, pq_flush_if_writable, proc_exit(), SetQueryCompletion(), shutdown_stream_done_queued, WalSnd::state, WALSNDSTATE_CATCHUP, WALSNDSTATE_STOPPING, WALSNDSTATE_STREAMING, WARNING, and whereToSendOutput.

Referenced by WalSndCheckShutdownTimeout().

WalSndErrorCleanup()

void WalSndErrorCleanup

(

void

)

Definition at line 377 of file walsender.c.

{
    LWLockReleaseAll();
    ConditionVariableCancelSleep();
    pgstat_report_wait_end();
    pgaio_error_cleanup();
 
    if (xlogreader != NULL && xlogreader->seg.ws_file >= 0)
        wal_segment_close(xlogreader);
 
    if (MyReplicationSlot != NULL)
        ReplicationSlotRelease();
 
    ReplicationSlotCleanup(false);
 
    replication_active = false;
 
    /*
     * If there is a transaction in progress, it will clean up our
     * ResourceOwner, but if a replication command set up a resource owner
     * without a transaction, we've got to clean that up now.
     */
    if (!IsTransactionOrTransactionBlock())
        ReleaseAuxProcessResources(false);
 
    if (got_STOPPING || got_SIGUSR2)
        proc_exit(0);
 
    /* Revert back to startup state */
    WalSndSetState(WALSNDSTATE_STARTUP);
}

References ConditionVariableCancelSleep(), fb(), got_SIGUSR2, got_STOPPING, IsTransactionOrTransactionBlock(), LWLockReleaseAll(), MyReplicationSlot, pgaio_error_cleanup(), pgstat_report_wait_end(), proc_exit(), ReleaseAuxProcessResources(), replication_active, ReplicationSlotCleanup(), ReplicationSlotRelease(), XLogReaderState::seg, wal_segment_close(), WalSndSetState(), WALSNDSTATE_STARTUP, WALOpenSegment::ws_file, and xlogreader.

Referenced by PostgresMain().

WalSndGetStateString()

static const char * WalSndGetStateString ( WalSndState  state )

static

Definition at line 4196 of file walsender.c.

{
    switch (state)
    {
        case WALSNDSTATE_STARTUP:
            return "startup";
        case WALSNDSTATE_BACKUP:
            return "backup";
        case WALSNDSTATE_CATCHUP:
            return "catchup";
        case WALSNDSTATE_STREAMING:
            return "streaming";
        case WALSNDSTATE_STOPPING:
            return "stopping";
    }
    return "UNKNOWN";
}

References WALSNDSTATE_BACKUP, WALSNDSTATE_CATCHUP, WALSNDSTATE_STARTUP, WALSNDSTATE_STOPPING, and WALSNDSTATE_STREAMING.

Referenced by pg_stat_get_wal_senders().

WalSndHandleConfigReload()

static void WalSndHandleConfigReload ( void  )

static

Definition at line 1679 of file walsender.c.

{
    if (!ConfigReloadPending)
        return;
 
    ConfigReloadPending = false;
    ProcessConfigFile(PGC_SIGHUP);
    SyncRepInitConfig();
 
    /*
     * Recheck and release any now-satisfied waiters after config reload
     * changes synchronous replication requirements (e.g., reducing the number
     * of sync standbys or changing the standby names).
     */
    if (!am_cascading_walsender)
        SyncRepReleaseWaiters();
}

References am_cascading_walsender, ConfigReloadPending, PGC_SIGHUP, ProcessConfigFile(), SyncRepInitConfig(), and SyncRepReleaseWaiters().

Referenced by ProcessPendingWrites(), WalSndLoop(), and WalSndWaitForWal().

WalSndInitStopping()

void WalSndInitStopping

(

void

)

Definition at line 4113 of file walsender.c.

{
    int         i;
 
    for (i = 0; i < max_wal_senders; i++)
    {
        WalSnd     *walsnd = &WalSndCtl->walsnds[i];
        pid_t       pid;
 
        SpinLockAcquire(&walsnd->mutex);
        pid = walsnd->pid;
        SpinLockRelease(&walsnd->mutex);
 
        if (pid == 0)
            continue;
 
        SendProcSignal(pid, PROCSIG_WALSND_INIT_STOPPING, INVALID_PROC_NUMBER);
    }
}

References fb(), i, INVALID_PROC_NUMBER, max_wal_senders, PROCSIG_WALSND_INIT_STOPPING, SendProcSignal(), SpinLockAcquire(), SpinLockRelease(), WalSndCtl, and WalSndCtlData::walsnds.

Referenced by ShutdownXLOG().

WalSndKeepalive()

static void WalSndKeepalive ( bool  requestReply, XLogRecPtr  writePtr  )

static

Definition at line 4402 of file walsender.c.

{
    elog(DEBUG2, "sending replication keepalive");
 
    /* construct the message... */
    resetStringInfo(&output_message);
    pq_sendbyte(&output_message, PqReplMsg_Keepalive);
    pq_sendint64(&output_message, XLogRecPtrIsValid(writePtr) ? writePtr : sentPtr);
    pq_sendint64(&output_message, GetCurrentTimestamp());
    pq_sendbyte(&output_message, requestReply ? 1 : 0);
 
    /* ... and send it wrapped in CopyData */
    pq_putmessage_noblock(PqMsg_CopyData, output_message.data, output_message.len);
 
    /* Set local flag */
    if (requestReply)
        waiting_for_ping_response = true;
}

References StringInfoData::data, DEBUG2, elog, fb(), GetCurrentTimestamp(), StringInfoData::len, output_message, pq_putmessage_noblock, pq_sendbyte(), pq_sendint64(), PqMsg_CopyData, PqReplMsg_Keepalive, resetStringInfo(), sentPtr, waiting_for_ping_response, and XLogRecPtrIsValid.

Referenced by ProcessStandbyReplyMessage(), WalSndDone(), WalSndKeepaliveIfNecessary(), WalSndUpdateProgress(), and WalSndWaitForWal().

WalSndKeepaliveIfNecessary()

static void WalSndKeepaliveIfNecessary ( void  )

static

Definition at line 4425 of file walsender.c.

{
    TimestampTz ping_time;
 
    /*
     * Don't send keepalive messages if timeouts are globally disabled or
     * we're doing something not partaking in timeouts.
     */
    if (wal_sender_timeout <= 0 || last_reply_timestamp <= 0)
        return;
 
    if (waiting_for_ping_response)
        return;
 
    /*
     * If half of wal_sender_timeout has lapsed without receiving any reply
     * from the standby, send a keep-alive message to the standby requesting
     * an immediate reply.
     */
    ping_time = TimestampTzPlusMilliseconds(last_reply_timestamp,
                                            wal_sender_timeout / 2);
    if (last_processing >= ping_time)
    {
        WalSndKeepalive(true, InvalidXLogRecPtr);
 
        /* Try to flush pending output to the client */
        if (pq_flush_if_writable() != 0)
            WalSndShutdown();
    }
}

References fb(), InvalidXLogRecPtr, last_processing, last_reply_timestamp, pq_flush_if_writable, TimestampTzPlusMilliseconds, waiting_for_ping_response, wal_sender_timeout, WalSndKeepalive(), and WalSndShutdown().

Referenced by ProcessPendingWrites(), WalSndLoop(), and WalSndWaitForWal().

WalSndKill()

static void WalSndKill ( int  code, Datum  arg  )

static

Definition at line 3250 of file walsender.c.

{
    WalSnd     *walsnd = MyWalSnd;
 
    Assert(walsnd != NULL);
 
    MyWalSnd = NULL;
 
    SpinLockAcquire(&walsnd->mutex);
    /* Mark WalSnd struct as no longer being in use. */
    walsnd->pid = 0;
    SpinLockRelease(&walsnd->mutex);
}

References Assert, fb(), MyWalSnd, SpinLockAcquire(), and SpinLockRelease().

Referenced by InitWalSenderSlot().

WalSndLastCycleHandler()

static void WalSndLastCycleHandler ( SIGNAL_ARGS  )

static

Definition at line 3960 of file walsender.c.

{
    got_SIGUSR2 = true;
    SetLatch(MyLatch);
}

References got_SIGUSR2, MyLatch, and SetLatch().

Referenced by WalSndSignals().

WalSndLoop()

static void WalSndLoop ( WalSndSendDataCallback  send_data )

static

Definition at line 3030 of file walsender.c.

{
    TimestampTz last_flush = 0;
 
    /*
     * Initialize the last reply timestamp. That enables timeout processing
     * from hereon.
     */
    last_reply_timestamp = GetCurrentTimestamp();
    waiting_for_ping_response = false;
 
    /*
     * Loop until we reach the end of this timeline or the client requests to
     * stop streaming.
     */
    for (;;)
    {
        /* Clear any already-pending wakeups */
        ResetLatch(MyLatch);
 
        CHECK_FOR_INTERRUPTS();
 
        /* Process any requests or signals received recently */
        WalSndHandleConfigReload();
 
        /* Check for input from the client */
        ProcessRepliesIfAny();
 
        /*
         * If we have received CopyDone from the client, sent CopyDone
         * ourselves, and the output buffer is empty, it's time to exit
         * streaming.
         */
        if (streamingDoneReceiving && streamingDoneSending &&
            !pq_is_send_pending())
            break;
 
        /*
         * If we don't have any pending data in the output buffer, try to send
         * some more.  If there is some, we don't bother to call send_data
         * again until we've flushed it ... but we'd better assume we are not
         * caught up.
         */
        if (!pq_is_send_pending())
            send_data();
        else
            WalSndCaughtUp = false;
 
        /* Try to flush pending output to the client */
        if (pq_flush_if_writable() != 0)
            WalSndShutdown();
 
        /* If nothing remains to be sent right now ... */
        if (WalSndCaughtUp && !pq_is_send_pending())
        {
            /*
             * If we're in catchup state, move to streaming.  This is an
             * important state change for users to know about, since before
             * this point data loss might occur if the primary dies and we
             * need to failover to the standby. The state change is also
             * important for synchronous replication, since commits that
             * started to wait at that point might wait for some time.
             */
            if (MyWalSnd->state == WALSNDSTATE_CATCHUP)
            {
                ereport(DEBUG1,
                        (errmsg_internal("\"%s\" has now caught up with upstream server",
                                         application_name)));
                WalSndSetState(WALSNDSTATE_STREAMING);
            }
 
            /*
             * When SIGUSR2 arrives, we send any outstanding logs up to the
             * shutdown checkpoint record (i.e., the latest record), wait for
             * them to be replicated to the standby, and exit. This may be a
             * normal termination at shutdown, or a promotion, the walsender
             * is not sure which.
             */
            if (got_SIGUSR2)
                WalSndDone(send_data);
        }
 
        /* Check for replication timeout. */
        WalSndCheckTimeOut();
 
        /*
         * During shutdown, die if the shutdown timeout expires. Call this
         * before WalSndComputeSleeptime() so the timeout is considered when
         * computing sleep time.
         */
        WalSndCheckShutdownTimeout();
 
        /* Send keepalive if the time has come */
        WalSndKeepaliveIfNecessary();
 
        /*
         * Block if we have unsent data.  XXX For logical replication, let
         * WalSndWaitForWal() handle any other blocking; idle receivers need
         * its additional actions.  For physical replication, also block if
         * caught up; its send_data does not block.
         *
         * The IO statistics are reported in WalSndWaitForWal() for the
         * logical WAL senders.
         */
        if ((WalSndCaughtUp && send_data != XLogSendLogical &&
             !streamingDoneSending) ||
            pq_is_send_pending())
        {
            long        sleeptime;
            int         wakeEvents;
            TimestampTz now;
 
            if (!streamingDoneReceiving)
                wakeEvents = WL_SOCKET_READABLE;
            else
                wakeEvents = 0;
 
            /*
             * Use fresh timestamp, not last_processing, to reduce the chance
             * of reaching wal_sender_timeout before sending a keepalive.
             */
            now = GetCurrentTimestamp();
            sleeptime = WalSndComputeSleeptime(now);
 
            if (pq_is_send_pending())
                wakeEvents |= WL_SOCKET_WRITEABLE;
 
            /* Report IO statistics, if needed */
            if (TimestampDifferenceExceeds(last_flush, now,
                                           WALSENDER_STATS_FLUSH_INTERVAL))
            {
                pgstat_flush_io(false);
                (void) pgstat_flush_backend(false, PGSTAT_BACKEND_FLUSH_IO);
                last_flush = now;
            }
 
            /* Sleep until something happens or we time out */
            WalSndWait(wakeEvents, sleeptime, WAIT_EVENT_WAL_SENDER_MAIN);
        }
    }
}

References application_name, CHECK_FOR_INTERRUPTS, DEBUG1, ereport, errmsg_internal(), fb(), GetCurrentTimestamp(), got_SIGUSR2, last_reply_timestamp, MyLatch, MyWalSnd, now(), PGSTAT_BACKEND_FLUSH_IO, pgstat_flush_backend(), pgstat_flush_io(), pq_flush_if_writable, pq_is_send_pending, ProcessRepliesIfAny(), ResetLatch(), WalSnd::state, streamingDoneReceiving, streamingDoneSending, TimestampDifferenceExceeds(), waiting_for_ping_response, WALSENDER_STATS_FLUSH_INTERVAL, WalSndCaughtUp, WalSndCheckShutdownTimeout(), WalSndCheckTimeOut(), WalSndComputeSleeptime(), WalSndDone(), WalSndHandleConfigReload(), WalSndKeepaliveIfNecessary(), WalSndSetState(), WalSndShutdown(), WALSNDSTATE_CATCHUP, WALSNDSTATE_STREAMING, WalSndWait(), WL_SOCKET_READABLE, WL_SOCKET_WRITEABLE, and XLogSendLogical().

Referenced by StartLogicalReplication(), and StartReplication().

WalSndPrepareWrite()

static void WalSndPrepareWrite ( LogicalDecodingContext *  ctx, XLogRecPtr  lsn, TransactionId  xid, bool  last_write  )

static

Definition at line 1607 of file walsender.c.

{
    /* can't have sync rep confused by sending the same LSN several times */
    if (!last_write)
        lsn = InvalidXLogRecPtr;
 
    resetStringInfo(ctx->out);
 
    pq_sendbyte(ctx->out, PqReplMsg_WALData);
    pq_sendint64(ctx->out, lsn);    /* dataStart */
    pq_sendint64(ctx->out, lsn);    /* walEnd */
 
    /*
     * Fill out the sendtime later, just as it's done in XLogSendPhysical, but
     * reserve space here.
     */
    pq_sendint64(ctx->out, 0);  /* sendtime */
}

References fb(), InvalidXLogRecPtr, LogicalDecodingContext::out, pq_sendbyte(), pq_sendint64(), PqReplMsg_WALData, and resetStringInfo().

Referenced by CreateReplicationSlot(), and StartLogicalReplication().

WalSndRqstFileReload()

void WalSndRqstFileReload

(

void

)

Definition at line 3913 of file walsender.c.

{
    int         i;
 
    for (i = 0; i < max_wal_senders; i++)
    {
        WalSnd     *walsnd = &WalSndCtl->walsnds[i];
 
        SpinLockAcquire(&walsnd->mutex);
        if (walsnd->pid == 0)
        {
            SpinLockRelease(&walsnd->mutex);
            continue;
        }
        walsnd->needreload = true;
        SpinLockRelease(&walsnd->mutex);
    }
}

References fb(), i, max_wal_senders, SpinLockAcquire(), SpinLockRelease(), WalSndCtl, and WalSndCtlData::walsnds.

Referenced by KeepFileRestoredFromArchive().

WalSndSegmentOpen()

static void WalSndSegmentOpen ( XLogReaderState *  state, XLogSegNo  nextSegNo, TimeLineID *  tli_p  )

static

Definition at line 3266 of file walsender.c.

{
    char        path[MAXPGPATH];
 
    /*-------
     * When reading from a historic timeline, and there is a timeline switch
     * within this segment, read from the WAL segment belonging to the new
     * timeline.
     *
     * For example, imagine that this server is currently on timeline 5, and
     * we're streaming timeline 4. The switch from timeline 4 to 5 happened at
     * 0/13002088. In pg_wal, we have these files:
     *
     * ...
     * 000000040000000000000012
     * 000000040000000000000013
     * 000000050000000000000013
     * 000000050000000000000014
     * ...
     *
     * In this situation, when requested to send the WAL from segment 0x13, on
     * timeline 4, we read the WAL from file 000000050000000000000013. Archive
     * recovery prefers files from newer timelines, so if the segment was
     * restored from the archive on this server, the file belonging to the old
     * timeline, 000000040000000000000013, might not exist. Their contents are
     * equal up to the switchpoint, because at a timeline switch, the used
     * portion of the old segment is copied to the new file.
     */
    *tli_p = sendTimeLine;
    if (sendTimeLineIsHistoric)
    {
        XLogSegNo   endSegNo;
 
        XLByteToSeg(sendTimeLineValidUpto, endSegNo, state->segcxt.ws_segsize);
        if (nextSegNo == endSegNo)
            *tli_p = sendTimeLineNextTLI;
    }
 
    XLogFilePath(path, *tli_p, nextSegNo, state->segcxt.ws_segsize);
    state->seg.ws_file = BasicOpenFile(path, O_RDONLY | PG_BINARY);
    if (state->seg.ws_file >= 0)
        return;
 
    /*
     * If the file is not found, assume it's because the standby asked for a
     * too old WAL segment that has already been removed or recycled.
     */
    if (errno == ENOENT)
    {
        char        xlogfname[MAXFNAMELEN];
        int         save_errno = errno;
 
        XLogFileName(xlogfname, *tli_p, nextSegNo, wal_segment_size);
        errno = save_errno;
        ereport(ERROR,
                (errcode_for_file_access(),
                 errmsg("requested WAL segment %s has already been removed",
                        xlogfname)));
    }
    else
        ereport(ERROR,
                (errcode_for_file_access(),
                 errmsg("could not open file \"%s\": %m",
                        path)));
}

References BasicOpenFile(), ereport, errcode_for_file_access(), errmsg, ERROR, fb(), MAXFNAMELEN, MAXPGPATH, PG_BINARY, sendTimeLine, sendTimeLineIsHistoric, sendTimeLineNextTLI, sendTimeLineValidUpto, wal_segment_size, XLByteToSeg, XLogFileName(), and XLogFilePath().

Referenced by CreateReplicationSlot(), StartLogicalReplication(), and StartReplication().

WalSndSetState()

void WalSndSetState

(

WalSndState

state

)

Definition at line 4177 of file walsender.c.

{
    WalSnd     *walsnd = MyWalSnd;
 
    Assert(am_walsender);
 
    if (walsnd->state == state)
        return;
 
    SpinLockAcquire(&walsnd->mutex);
    walsnd->state = state;
    SpinLockRelease(&walsnd->mutex);
}

References am_walsender, Assert, fb(), MyWalSnd, SpinLockAcquire(), and SpinLockRelease().

Referenced by exec_replication_command(), SendBaseBackup(), StartLogicalReplication(), StartReplication(), WalSndErrorCleanup(), WalSndLoop(), and XLogSendPhysical().

WalSndShmemInit()

static void WalSndShmemInit ( void *  arg )

static

Definition at line 4001 of file walsender.c.

{
    for (int i = 0; i < NUM_SYNC_REP_WAIT_MODE; i++)
        dlist_init(&(WalSndCtl->SyncRepQueue[i]));
 
    for (int i = 0; i < max_wal_senders; i++)
    {
        WalSnd     *walsnd = &WalSndCtl->walsnds[i];
 
        SpinLockInit(&walsnd->mutex);
    }
 
    ConditionVariableInit(&WalSndCtl->wal_flush_cv);
    ConditionVariableInit(&WalSndCtl->wal_replay_cv);
    ConditionVariableInit(&WalSndCtl->wal_confirm_rcv_cv);
}

References ConditionVariableInit(), dlist_init(), fb(), i, max_wal_senders, NUM_SYNC_REP_WAIT_MODE, SpinLockInit(), WalSndCtlData::SyncRepQueue, WalSndCtlData::wal_confirm_rcv_cv, WalSndCtlData::wal_flush_cv, WalSndCtlData::wal_replay_cv, WalSndCtl, and WalSndCtlData::walsnds.

WalSndShmemRequest()

static void WalSndShmemRequest ( void *  arg )

static

Definition at line 3987 of file walsender.c.

{
    Size        size;
 
    size = offsetof(WalSndCtlData, walsnds);
    size = add_size(size, mul_size(max_wal_senders, sizeof(WalSnd)));
    ShmemRequestStruct(.name = "Wal Sender Ctl",
                       .size = size,
                       .ptr = (void **) &WalSndCtl,
        );
}

References add_size(), fb(), max_wal_senders, mul_size(), name, ShmemRequestStruct, and WalSndCtl.

WalSndShutdown()

static void WalSndShutdown ( void  )

static

Definition at line 413 of file walsender.c.

{
    /*
     * Reset whereToSendOutput to prevent ereport from attempting to send any
     * more messages to the standby.
     */
    if (whereToSendOutput == DestRemote)
        whereToSendOutput = DestNone;
 
    proc_exit(0);
}

References DestNone, DestRemote, proc_exit(), and whereToSendOutput.

Referenced by ProcessPendingWrites(), WalSndCheckTimeOut(), WalSndDone(), WalSndKeepaliveIfNecessary(), WalSndLoop(), WalSndUpdateProgress(), WalSndWaitForWal(), and WalSndWriteData().

WalSndSignals()

void WalSndSignals

(

void

)

Definition at line 3968 of file walsender.c.

{
    /* Set up signal handlers */
    pqsignal(SIGHUP, SignalHandlerForConfigReload);
    pqsignal(SIGINT, StatementCancelHandler);   /* query cancel */
    pqsignal(SIGTERM, die);     /* request shutdown */
    /* SIGQUIT handler was already set up by InitPostmasterChild */
    InitializeTimeouts();       /* establishes SIGALRM handler */
    pqsignal(SIGPIPE, PG_SIG_IGN);
    pqsignal(SIGUSR1, procsignal_sigusr1_handler);
    pqsignal(SIGUSR2, WalSndLastCycleHandler);  /* request a last cycle and
                                                 * shutdown */
 
    /* Reset some signals that are accepted by postmaster but not here */
    pqsignal(SIGCHLD, PG_SIG_DFL);
}

References die, fb(), InitializeTimeouts(), PG_SIG_DFL, PG_SIG_IGN, pqsignal, procsignal_sigusr1_handler(), SIGCHLD, SIGHUP, SignalHandlerForConfigReload(), SIGPIPE, SIGUSR1, SIGUSR2, StatementCancelHandler(), and WalSndLastCycleHandler().

Referenced by PostgresMain().

WalSndUpdateProgress()

static void WalSndUpdateProgress ( LogicalDecodingContext *  ctx, XLogRecPtr  lsn, TransactionId  xid, bool  skipped_xact  )

static

Definition at line 1758 of file walsender.c.

{
    static TimestampTz sendTime = 0;
    TimestampTz now = GetCurrentTimestamp();
    bool        pending_writes = false;
    bool        end_xact = ctx->end_xact;
 
    /*
     * Track lag no more than once per WALSND_LOGICAL_LAG_TRACK_INTERVAL_MS to
     * avoid flooding the lag tracker when we commit frequently.
     *
     * We don't have a mechanism to get the ack for any LSN other than end
     * xact LSN from the downstream. So, we track lag only for end of
     * transaction LSN.
     */
#define WALSND_LOGICAL_LAG_TRACK_INTERVAL_MS    1000
    if (end_xact && TimestampDifferenceExceeds(sendTime, now,
                                               WALSND_LOGICAL_LAG_TRACK_INTERVAL_MS))
    {
        LagTrackerWrite(lsn, now);
        sendTime = now;
    }
 
    /*
     * When skipping empty transactions in synchronous replication, we send a
     * keepalive message to avoid delaying such transactions.
     *
     * It is okay to check sync_standbys_status without lock here as in the
     * worst case we will just send an extra keepalive message when it is
     * really not required.
     */
    if (skipped_xact &&
        SyncRepRequested() &&
        (((volatile WalSndCtlData *) WalSndCtl)->sync_standbys_status & SYNC_STANDBY_DEFINED))
    {
        WalSndKeepalive(false, lsn);
 
        /* Try to flush pending output to the client */
        if (pq_flush_if_writable() != 0)
            WalSndShutdown();
 
        /* If we have pending write here, make sure it's actually flushed */
        if (pq_is_send_pending())
            pending_writes = true;
    }
 
    /*
     * Process pending writes if any or try to send a keepalive if required.
     * We don't need to try sending keep alive messages at the transaction end
     * as that will be done at a later point in time. This is required only
     * for large transactions where we don't send any changes to the
     * downstream and the receiver can timeout due to that.
     */
    if (pending_writes || (!end_xact &&
                           now >= TimestampTzPlusMilliseconds(last_reply_timestamp,
                                                              wal_sender_timeout / 2)))
        ProcessPendingWrites();
}

References LogicalDecodingContext::end_xact, fb(), GetCurrentTimestamp(), LagTrackerWrite(), last_reply_timestamp, now(), pq_flush_if_writable, pq_is_send_pending, ProcessPendingWrites(), SYNC_STANDBY_DEFINED, SyncRepRequested, TimestampDifferenceExceeds(), TimestampTzPlusMilliseconds, wal_sender_timeout, WALSND_LOGICAL_LAG_TRACK_INTERVAL_MS, WalSndCtl, WalSndKeepalive(), and WalSndShutdown().

Referenced by CreateReplicationSlot(), and StartLogicalReplication().

WalSndWait()

static void WalSndWait ( uint32  socket_events, long  timeout, uint32  wait_event  )

static

Definition at line 4055 of file walsender.c.

{
    WaitEvent   event;
 
    ModifyWaitEvent(FeBeWaitSet, FeBeWaitSetSocketPos, socket_events, NULL);
 
    /*
     * We use a condition variable to efficiently wake up walsenders in
     * WalSndWakeup().
     *
     * Every walsender prepares to sleep on a shared memory CV. Note that it
     * just prepares to sleep on the CV (i.e., adds itself to the CV's
     * waitlist), but does not actually wait on the CV (IOW, it never calls
     * ConditionVariableSleep()). It still uses WaitEventSetWait() for
     * waiting, because we also need to wait for socket events. The processes
     * (startup process, walreceiver etc.) wanting to wake up walsenders use
     * ConditionVariableBroadcast(), which in turn calls SetLatch(), helping
     * walsenders come out of WaitEventSetWait().
     *
     * This approach is simple and efficient because, one doesn't have to loop
     * through all the walsenders slots, with a spinlock acquisition and
     * release for every iteration, just to wake up only the waiting
     * walsenders. It makes WalSndWakeup() callers' life easy.
     *
     * XXX: A desirable future improvement would be to add support for CVs
     * into WaitEventSetWait().
     *
     * And, we use separate shared memory CVs for physical and logical
     * walsenders for selective wake ups, see WalSndWakeup() for more details.
     *
     * If the wait event is WAIT_FOR_STANDBY_CONFIRMATION, wait on another CV
     * until awakened by physical walsenders after the walreceiver confirms
     * the receipt of the LSN.
     */
    if (wait_event == WAIT_EVENT_WAIT_FOR_STANDBY_CONFIRMATION)
        ConditionVariablePrepareToSleep(&WalSndCtl->wal_confirm_rcv_cv);
    else if (MyWalSnd->kind == REPLICATION_KIND_PHYSICAL)
        ConditionVariablePrepareToSleep(&WalSndCtl->wal_flush_cv);
    else if (MyWalSnd->kind == REPLICATION_KIND_LOGICAL)
        ConditionVariablePrepareToSleep(&WalSndCtl->wal_replay_cv);
 
    if (WaitEventSetWait(FeBeWaitSet, timeout, &event, 1, wait_event) == 1 &&
        (event.events & WL_POSTMASTER_DEATH))
    {
        ConditionVariableCancelSleep();
        proc_exit(1);
    }
 
    ConditionVariableCancelSleep();
}

References ConditionVariableCancelSleep(), ConditionVariablePrepareToSleep(), WaitEvent::events, fb(), FeBeWaitSet, FeBeWaitSetSocketPos, WalSnd::kind, ModifyWaitEvent(), MyWalSnd, proc_exit(), REPLICATION_KIND_LOGICAL, REPLICATION_KIND_PHYSICAL, WaitEventSetWait(), WalSndCtlData::wal_confirm_rcv_cv, WalSndCtlData::wal_flush_cv, WalSndCtlData::wal_replay_cv, WalSndCtl, and WL_POSTMASTER_DEATH.

Referenced by ProcessPendingWrites(), WalSndDone(), WalSndLoop(), and WalSndWaitForWal().

WalSndWaitForWal()

static XLogRecPtr WalSndWaitForWal ( XLogRecPtr  loc )

static

Definition at line 1908 of file walsender.c.

{
    int         wakeEvents;
    uint32      wait_event = 0;
    static XLogRecPtr RecentFlushPtr = InvalidXLogRecPtr;
    TimestampTz last_flush = 0;
 
    /*
     * Fast path to avoid acquiring the spinlock in case we already know we
     * have enough WAL available and all the standby servers have confirmed
     * receipt of WAL up to RecentFlushPtr. This is particularly interesting
     * if we're far behind.
     */
    if (XLogRecPtrIsValid(RecentFlushPtr) &&
        !NeedToWaitForWal(loc, RecentFlushPtr, &wait_event))
        return RecentFlushPtr;
 
    /*
     * Within the loop, we wait for the necessary WALs to be flushed to disk
     * first, followed by waiting for standbys to catch up if there are enough
     * WALs (see NeedToWaitForWal()) or upon receiving the shutdown signal.
     */
    for (;;)
    {
        bool        wait_for_standby_at_stop = false;
        long        sleeptime;
        TimestampTz now;
 
        /* Clear any already-pending wakeups */
        ResetLatch(MyLatch);
 
        CHECK_FOR_INTERRUPTS();
 
        /* Process any requests or signals received recently */
        WalSndHandleConfigReload();
 
        /* Check for input from the client */
        ProcessRepliesIfAny();
 
        /*
         * If we're shutting down, trigger pending WAL to be written out,
         * otherwise we'd possibly end up waiting for WAL that never gets
         * written, because walwriter has shut down already.
         *
         * Note that GetXLogInsertEndRecPtr() is used to obtain the WAL flush
         * request location instead of GetXLogInsertRecPtr(). Because if the
         * last WAL record ends at a page boundary, GetXLogInsertRecPtr() can
         * return an LSN pointing past the page header, which may cause
         * XLogFlush() to report an error.
         */
        if (got_STOPPING && !RecoveryInProgress())
            XLogFlush(GetXLogInsertEndRecPtr());
 
        /*
         * To avoid the scenario where standbys need to catch up to a newer
         * WAL location in each iteration, we update our idea of the currently
         * flushed position only if we are not waiting for standbys to catch
         * up.
         */
        if (wait_event != WAIT_EVENT_WAIT_FOR_STANDBY_CONFIRMATION)
        {
            if (!RecoveryInProgress())
                RecentFlushPtr = GetFlushRecPtr(NULL);
            else
                RecentFlushPtr = GetXLogReplayRecPtr(NULL);
        }
 
        /*
         * If postmaster asked us to stop and the standby slots have caught up
         * to the flushed position, don't wait anymore.
         *
         * It's important to do this check after the recomputation of
         * RecentFlushPtr, so we can send all remaining data before shutting
         * down.
         */
        if (got_STOPPING)
        {
            if (NeedToWaitForStandbys(RecentFlushPtr, &wait_event))
                wait_for_standby_at_stop = true;
            else
                break;
        }
 
        /*
         * We only send regular messages to the client for full decoded
         * transactions, but a synchronous replication and walsender shutdown
         * possibly are waiting for a later location. So, before sleeping, we
         * send a ping containing the flush location. If the receiver is
         * otherwise idle, this keepalive will trigger a reply. Processing the
         * reply will update these MyWalSnd locations.
         */
        if (MyWalSnd->flush < sentPtr &&
            MyWalSnd->write < sentPtr &&
            !waiting_for_ping_response)
            WalSndKeepalive(false, InvalidXLogRecPtr);
 
        /*
         * Exit the loop if already caught up and doesn't need to wait for
         * standby slots.
         */
        if (!wait_for_standby_at_stop &&
            !NeedToWaitForWal(loc, RecentFlushPtr, &wait_event))
            break;
 
        /*
         * Waiting for new WAL or waiting for standbys to catch up. Since we
         * need to wait, we're now caught up.
         */
        WalSndCaughtUp = true;
 
        /*
         * Try to flush any pending output to the client.
         */
        if (pq_flush_if_writable() != 0)
            WalSndShutdown();
 
        /*
         * If we have received CopyDone from the client, sent CopyDone
         * ourselves, and the output buffer is empty, it's time to exit
         * streaming, so fail the current WAL fetch request.
         */
        if (streamingDoneReceiving && streamingDoneSending &&
            !pq_is_send_pending())
            break;
 
        /* die if timeout was reached */
        WalSndCheckTimeOut();
 
        /*
         * During shutdown, die if the shutdown timeout expires. Call this
         * before WalSndComputeSleeptime() so the timeout is considered when
         * computing sleep time.
         */
        WalSndCheckShutdownTimeout();
 
        /* Send keepalive if the time has come */
        WalSndKeepaliveIfNecessary();
 
        /*
         * Sleep until something happens or we time out.  Also wait for the
         * socket becoming writable, if there's still pending output.
         * Otherwise we might sit on sendable output data while waiting for
         * new WAL to be generated.  (But if we have nothing to send, we don't
         * want to wake on socket-writable.)
         */
        now = GetCurrentTimestamp();
        sleeptime = WalSndComputeSleeptime(now);
 
        wakeEvents = WL_SOCKET_READABLE;
 
        if (pq_is_send_pending())
            wakeEvents |= WL_SOCKET_WRITEABLE;
 
        Assert(wait_event != 0);
 
        /* Report IO statistics, if needed */
        if (TimestampDifferenceExceeds(last_flush, now,
                                       WALSENDER_STATS_FLUSH_INTERVAL))
        {
            pgstat_flush_io(false);
            (void) pgstat_flush_backend(false, PGSTAT_BACKEND_FLUSH_IO);
            last_flush = now;
        }
 
        WalSndWait(wakeEvents, sleeptime, wait_event);
    }
 
    /* reactivate latch so WalSndLoop knows to continue */
    SetLatch(MyLatch);
    return RecentFlushPtr;
}

References Assert, CHECK_FOR_INTERRUPTS, fb(), WalSnd::flush, GetCurrentTimestamp(), GetFlushRecPtr(), GetXLogInsertEndRecPtr(), GetXLogReplayRecPtr(), got_STOPPING, InvalidXLogRecPtr, MyLatch, MyWalSnd, NeedToWaitForStandbys(), NeedToWaitForWal(), now(), PGSTAT_BACKEND_FLUSH_IO, pgstat_flush_backend(), pgstat_flush_io(), pq_flush_if_writable, pq_is_send_pending, ProcessRepliesIfAny(), RecoveryInProgress(), ResetLatch(), sentPtr, SetLatch(), streamingDoneReceiving, streamingDoneSending, TimestampDifferenceExceeds(), waiting_for_ping_response, WALSENDER_STATS_FLUSH_INTERVAL, WalSndCaughtUp, WalSndCheckShutdownTimeout(), WalSndCheckTimeOut(), WalSndComputeSleeptime(), WalSndHandleConfigReload(), WalSndKeepalive(), WalSndKeepaliveIfNecessary(), WalSndShutdown(), WalSndWait(), WL_SOCKET_READABLE, WL_SOCKET_WRITEABLE, WalSnd::write, XLogFlush(), and XLogRecPtrIsValid.

Referenced by logical_read_xlog_page().

WalSndWaitStopping()

void WalSndWaitStopping

(

void

)

Definition at line 4139 of file walsender.c.

{
    for (;;)
    {
        int         i;
        bool        all_stopped = true;
 
        for (i = 0; i < max_wal_senders; i++)
        {
            WalSnd     *walsnd = &WalSndCtl->walsnds[i];
 
            SpinLockAcquire(&walsnd->mutex);
 
            if (walsnd->pid == 0)
            {
                SpinLockRelease(&walsnd->mutex);
                continue;
            }
 
            if (walsnd->state != WALSNDSTATE_STOPPING)
            {
                all_stopped = false;
                SpinLockRelease(&walsnd->mutex);
                break;
            }
            SpinLockRelease(&walsnd->mutex);
        }
 
        /* safe to leave if confirmation is done for all WAL senders */
        if (all_stopped)
            return;
 
        pg_usleep(10000L);      /* wait for 10 msec */
    }
}

References fb(), i, max_wal_senders, pg_usleep(), SpinLockAcquire(), SpinLockRelease(), WalSndCtl, WalSndCtlData::walsnds, and WALSNDSTATE_STOPPING.

Referenced by ShutdownXLOG().

WalSndWakeup()

void WalSndWakeup	(	bool	physical,
		bool	logical
	)

Definition at line 4034 of file walsender.c.

{
    /*
     * Wake up all the walsenders waiting on WAL being flushed or replayed
     * respectively.  Note that waiting walsender would have prepared to sleep
     * on the CV (i.e., added itself to the CV's waitlist) in WalSndWait()
     * before actually waiting.
     */
    if (physical)
        ConditionVariableBroadcast(&WalSndCtl->wal_flush_cv);
 
    if (logical)
        ConditionVariableBroadcast(&WalSndCtl->wal_replay_cv);
}

References ConditionVariableBroadcast(), WalSndCtlData::wal_flush_cv, WalSndCtlData::wal_replay_cv, and WalSndCtl.

Referenced by ApplyWalRecord(), KeepFileRestoredFromArchive(), StartupXLOG(), WalSndWakeupProcessRequests(), and XLogWalRcvFlush().

WalSndWriteData()

static void WalSndWriteData ( LogicalDecodingContext *  ctx, XLogRecPtr  lsn, TransactionId  xid, bool  last_write  )

static

Definition at line 1634 of file walsender.c.

{
    TimestampTz now;
 
    /*
     * Fill the send timestamp last, so that it is taken as late as possible.
     * This is somewhat ugly, but the protocol is set as it's already used for
     * several releases by streaming physical replication.
     */
    resetStringInfo(&tmpbuf);
    now = GetCurrentTimestamp();
    pq_sendint64(&tmpbuf, now);
    memcpy(&ctx->out->data[1 + sizeof(int64) + sizeof(int64)],
           tmpbuf.data, sizeof(int64));
 
    /* output previously gathered data in a CopyData packet */
    pq_putmessage_noblock(PqMsg_CopyData, ctx->out->data, ctx->out->len);
 
    CHECK_FOR_INTERRUPTS();
 
    /* Try to flush pending output to the client */
    if (pq_flush_if_writable() != 0)
        WalSndShutdown();
 
    /* Try taking fast path unless we get too close to walsender timeout. */
    if (now < TimestampTzPlusMilliseconds(last_reply_timestamp,
                                          wal_sender_timeout / 2) &&
        !pq_is_send_pending())
    {
        return;
    }
 
    /* If we have pending write here, go to slow path */
    ProcessPendingWrites();
}

References CHECK_FOR_INTERRUPTS, StringInfoData::data, GetCurrentTimestamp(), last_reply_timestamp, StringInfoData::len, memcpy(), now(), LogicalDecodingContext::out, pq_flush_if_writable, pq_is_send_pending, pq_putmessage_noblock, pq_sendint64(), PqMsg_CopyData, ProcessPendingWrites(), resetStringInfo(), TimestampTzPlusMilliseconds, tmpbuf, wal_sender_timeout, and WalSndShutdown().

Referenced by CreateReplicationSlot(), and StartLogicalReplication().

XLogSendLogical()

static void XLogSendLogical ( void  )

static

Definition at line 3654 of file walsender.c.

{
    XLogRecord *record;
    char       *errm;
 
    /*
     * We'll use the current flush point to determine whether we've caught up.
     * This variable is static in order to cache it across calls.  Caching is
     * helpful because GetFlushRecPtr() needs to acquire a heavily-contended
     * spinlock.
     */
    static XLogRecPtr flushPtr = InvalidXLogRecPtr;
 
    /*
     * Don't know whether we've caught up yet. We'll set WalSndCaughtUp to
     * true in WalSndWaitForWal, if we're actually waiting. We also set to
     * true if XLogReadRecord() had to stop reading but WalSndWaitForWal
     * didn't wait - i.e. when we're shutting down.
     */
    WalSndCaughtUp = false;
 
    record = XLogReadRecord(logical_decoding_ctx->reader, &errm);
 
    /* xlog record was invalid */
    if (errm != NULL)
        elog(ERROR, "could not find record while sending logically-decoded data: %s",
             errm);
 
    if (record != NULL)
    {
        /*
         * Note the lack of any call to LagTrackerWrite() which is handled by
         * WalSndUpdateProgress which is called by output plugin through
         * logical decoding write api.
         */
        LogicalDecodingProcessRecord(logical_decoding_ctx, logical_decoding_ctx->reader);
 
        sentPtr = logical_decoding_ctx->reader->EndRecPtr;
    }
 
    /*
     * If first time through in this session, initialize flushPtr.  Otherwise,
     * we only need to update flushPtr if EndRecPtr is past it.
     */
    if (!XLogRecPtrIsValid(flushPtr) ||
        logical_decoding_ctx->reader->EndRecPtr >= flushPtr)
    {
        /*
         * For cascading logical WAL senders, we use the replay LSN instead of
         * the flush LSN, since logical decoding on a standby only processes
         * WAL that has been replayed.  This distinction becomes particularly
         * important during shutdown, as new WAL is no longer replayed and the
         * last replayed LSN marks the furthest point up to which decoding can
         * proceed.
         */
        if (am_cascading_walsender)
            flushPtr = GetXLogReplayRecPtr(NULL);
        else
            flushPtr = GetFlushRecPtr(NULL);
    }
 
    /* If EndRecPtr is still past our flushPtr, it means we caught up. */
    if (logical_decoding_ctx->reader->EndRecPtr >= flushPtr)
        WalSndCaughtUp = true;
 
    /*
     * If we're caught up and have been requested to stop, have WalSndLoop()
     * terminate the connection in an orderly manner, after writing out all
     * the pending data.
     */
    if (WalSndCaughtUp && got_STOPPING)
        got_SIGUSR2 = true;
 
    /* Update shared memory status */
    {
        WalSnd     *walsnd = MyWalSnd;
 
        SpinLockAcquire(&walsnd->mutex);
        walsnd->sentPtr = sentPtr;
        SpinLockRelease(&walsnd->mutex);
    }
}

References am_cascading_walsender, elog, XLogReaderState::EndRecPtr, ERROR, fb(), GetFlushRecPtr(), GetXLogReplayRecPtr(), got_SIGUSR2, got_STOPPING, InvalidXLogRecPtr, logical_decoding_ctx, LogicalDecodingProcessRecord(), MyWalSnd, LogicalDecodingContext::reader, sentPtr, SpinLockAcquire(), SpinLockRelease(), WalSndCaughtUp, XLogReadRecord(), and XLogRecPtrIsValid.

Referenced by StartLogicalReplication(), and WalSndLoop().

XLogSendPhysical()

static void XLogSendPhysical ( void  )

static

Definition at line 3344 of file walsender.c.

{
    XLogRecPtr  SendRqstPtr;
    XLogRecPtr  startptr;
    XLogRecPtr  endptr;
    Size        nbytes;
    XLogSegNo   segno;
    WALReadError errinfo;
    Size        rbytes;
 
    /* If requested switch the WAL sender to the stopping state. */
    if (got_STOPPING)
        WalSndSetState(WALSNDSTATE_STOPPING);
 
    if (streamingDoneSending)
    {
        WalSndCaughtUp = true;
        return;
    }
 
    /* Figure out how far we can safely send the WAL. */
    if (sendTimeLineIsHistoric)
    {
        /*
         * Streaming an old timeline that's in this server's history, but is
         * not the one we're currently inserting or replaying. It can be
         * streamed up to the point where we switched off that timeline.
         */
        SendRqstPtr = sendTimeLineValidUpto;
    }
    else if (am_cascading_walsender)
    {
        TimeLineID  SendRqstTLI;
 
        /*
         * Streaming the latest timeline on a standby.
         *
         * Attempt to send all WAL that has already been replayed, so that we
         * know it's valid. If we're receiving WAL through streaming
         * replication, it's also OK to send any WAL that has been received
         * but not replayed.
         *
         * The timeline we're recovering from can change, or we can be
         * promoted. In either case, the current timeline becomes historic. We
         * need to detect that so that we don't try to stream past the point
         * where we switched to another timeline. We check for promotion or
         * timeline switch after calculating FlushPtr, to avoid a race
         * condition: if the timeline becomes historic just after we checked
         * that it was still current, it's still be OK to stream it up to the
         * FlushPtr that was calculated before it became historic.
         */
        bool        becameHistoric = false;
 
        SendRqstPtr = GetStandbyFlushRecPtr(&SendRqstTLI);
 
        if (!RecoveryInProgress())
        {
            /* We have been promoted. */
            SendRqstTLI = GetWALInsertionTimeLine();
            am_cascading_walsender = false;
            becameHistoric = true;
        }
        else
        {
            /*
             * Still a cascading standby. But is the timeline we're sending
             * still the one recovery is recovering from?
             */
            if (sendTimeLine != SendRqstTLI)
                becameHistoric = true;
        }
 
        if (becameHistoric)
        {
            /*
             * The timeline we were sending has become historic. Read the
             * timeline history file of the new timeline to see where exactly
             * we forked off from the timeline we were sending.
             */
            List       *history;
 
            history = readTimeLineHistory(SendRqstTLI);
            sendTimeLineValidUpto = tliSwitchPoint(sendTimeLine, history, &sendTimeLineNextTLI);
 
            Assert(sendTimeLine < sendTimeLineNextTLI);
            list_free_deep(history);
 
            sendTimeLineIsHistoric = true;
 
            SendRqstPtr = sendTimeLineValidUpto;
        }
    }
    else
    {
        /*
         * Streaming the current timeline on a primary.
         *
         * Attempt to send all data that's already been written out and
         * fsync'd to disk.  We cannot go further than what's been written out
         * given the current implementation of WALRead().  And in any case
         * it's unsafe to send WAL that is not securely down to disk on the
         * primary: if the primary subsequently crashes and restarts, standbys
         * must not have applied any WAL that got lost on the primary.
         */
        SendRqstPtr = GetFlushRecPtr(NULL);
    }
 
    /*
     * Record the current system time as an approximation of the time at which
     * this WAL location was written for the purposes of lag tracking.
     *
     * In theory we could make XLogFlush() record a time in shmem whenever WAL
     * is flushed and we could get that time as well as the LSN when we call
     * GetFlushRecPtr() above (and likewise for the cascading standby
     * equivalent), but rather than putting any new code into the hot WAL path
     * it seems good enough to capture the time here.  We should reach this
     * after XLogFlush() runs WalSndWakeupProcessRequests(), and although that
     * may take some time, we read the WAL flush pointer and take the time
     * very close to together here so that we'll get a later position if it is
     * still moving.
     *
     * Because LagTrackerWrite ignores samples when the LSN hasn't advanced,
     * this gives us a cheap approximation for the WAL flush time for this
     * LSN.
     *
     * Note that the LSN is not necessarily the LSN for the data contained in
     * the present message; it's the end of the WAL, which might be further
     * ahead.  All the lag tracking machinery cares about is finding out when
     * that arbitrary LSN is eventually reported as written, flushed and
     * applied, so that it can measure the elapsed time.
     */
    LagTrackerWrite(SendRqstPtr, GetCurrentTimestamp());
 
    /*
     * If this is a historic timeline and we've reached the point where we
     * forked to the next timeline, stop streaming.
     *
     * Note: We might already have sent WAL > sendTimeLineValidUpto. The
     * startup process will normally replay all WAL that has been received
     * from the primary, before promoting, but if the WAL streaming is
     * terminated at a WAL page boundary, the valid portion of the timeline
     * might end in the middle of a WAL record. We might've already sent the
     * first half of that partial WAL record to the cascading standby, so that
     * sentPtr > sendTimeLineValidUpto. That's OK; the cascading standby can't
     * replay the partial WAL record either, so it can still follow our
     * timeline switch.
     */
    if (sendTimeLineIsHistoric && sendTimeLineValidUpto <= sentPtr)
    {
        /* close the current file. */
        if (xlogreader->seg.ws_file >= 0)
            wal_segment_close(xlogreader);
 
        /* Send CopyDone */
        pq_putmessage_noblock(PqMsg_CopyDone, NULL, 0);
        streamingDoneSending = true;
 
        WalSndCaughtUp = true;
 
        elog(DEBUG1, "walsender reached end of timeline at %X/%08X (sent up to %X/%08X)",
             LSN_FORMAT_ARGS(sendTimeLineValidUpto),
             LSN_FORMAT_ARGS(sentPtr));
        return;
    }
 
    /* Do we have any work to do? */
    Assert(sentPtr <= SendRqstPtr);
    if (SendRqstPtr <= sentPtr)
    {
        WalSndCaughtUp = true;
        return;
    }
 
    /*
     * Figure out how much to send in one message. If there's no more than
     * MAX_SEND_SIZE bytes to send, send everything. Otherwise send
     * MAX_SEND_SIZE bytes, but round back to logfile or page boundary.
     *
     * The rounding is not only for performance reasons. Walreceiver relies on
     * the fact that we never split a WAL record across two messages. Since a
     * long WAL record is split at page boundary into continuation records,
     * page boundary is always a safe cut-off point. We also assume that
     * SendRqstPtr never points to the middle of a WAL record.
     */
    startptr = sentPtr;
    endptr = startptr;
    endptr += MAX_SEND_SIZE;
 
    /* if we went beyond SendRqstPtr, back off */
    if (SendRqstPtr <= endptr)
    {
        endptr = SendRqstPtr;
        if (sendTimeLineIsHistoric)
            WalSndCaughtUp = false;
        else
            WalSndCaughtUp = true;
    }
    else
    {
        /* round down to page boundary. */
        endptr -= (endptr % XLOG_BLCKSZ);
        WalSndCaughtUp = false;
    }
 
    nbytes = endptr - startptr;
    Assert(nbytes <= MAX_SEND_SIZE);
 
    /*
     * OK to read and send the slice.
     */
    resetStringInfo(&output_message);
    pq_sendbyte(&output_message, PqReplMsg_WALData);
 
    pq_sendint64(&output_message, startptr);    /* dataStart */
    pq_sendint64(&output_message, SendRqstPtr); /* walEnd */
    pq_sendint64(&output_message, 0);   /* sendtime, filled in last */
 
    /*
     * Read the log directly into the output buffer to avoid extra memcpy
     * calls.
     */
    enlargeStringInfo(&output_message, nbytes);
 
retry:
    /* attempt to read WAL from WAL buffers first */
    rbytes = WALReadFromBuffers(&output_message.data[output_message.len],
                                startptr, nbytes, xlogreader->seg.ws_tli);
    output_message.len += rbytes;
    startptr += rbytes;
    nbytes -= rbytes;
 
    /* now read the remaining WAL from WAL file */
    if (nbytes > 0 &&
        !WALRead(xlogreader,
                 &output_message.data[output_message.len],
                 startptr,
                 nbytes,
                 xlogreader->seg.ws_tli,    /* Pass the current TLI because
                                             * only WalSndSegmentOpen controls
                                             * whether new TLI is needed. */
                 &errinfo))
        WALReadRaiseError(&errinfo);
 
    /* See logical_read_xlog_page(). */
    XLByteToSeg(startptr, segno, xlogreader->segcxt.ws_segsize);
    CheckXLogRemoved(segno, xlogreader->seg.ws_tli);
 
    /*
     * During recovery, the currently-open WAL file might be replaced with the
     * file of the same name retrieved from archive. So we always need to
     * check what we read was valid after reading into the buffer. If it's
     * invalid, we try to open and read the file again.
     */
    if (am_cascading_walsender)
    {
        WalSnd     *walsnd = MyWalSnd;
        bool        reload;
 
        SpinLockAcquire(&walsnd->mutex);
        reload = walsnd->needreload;
        walsnd->needreload = false;
        SpinLockRelease(&walsnd->mutex);
 
        if (reload && xlogreader->seg.ws_file >= 0)
        {
            wal_segment_close(xlogreader);
 
            goto retry;
        }
    }
 
    output_message.len += nbytes;
    output_message.data[output_message.len] = '\0';
 
    /*
     * Fill the send timestamp last, so that it is taken as late as possible.
     */
    resetStringInfo(&tmpbuf);
    pq_sendint64(&tmpbuf, GetCurrentTimestamp());
    memcpy(&output_message.data[1 + sizeof(int64) + sizeof(int64)],
           tmpbuf.data, sizeof(int64));
 
    pq_putmessage_noblock(PqMsg_CopyData, output_message.data, output_message.len);
 
    sentPtr = endptr;
 
    /* Update shared memory status */
    {
        WalSnd     *walsnd = MyWalSnd;
 
        SpinLockAcquire(&walsnd->mutex);
        walsnd->sentPtr = sentPtr;
        SpinLockRelease(&walsnd->mutex);
    }
 
    /* Report progress of XLOG streaming in PS display */
    if (update_process_title)
    {
        char        activitymsg[50];
 
        snprintf(activitymsg, sizeof(activitymsg), "streaming %X/%08X",
                 LSN_FORMAT_ARGS(sentPtr));
        set_ps_display(activitymsg);
    }
}

References am_cascading_walsender, Assert, CheckXLogRemoved(), StringInfoData::data, DEBUG1, elog, enlargeStringInfo(), fb(), GetCurrentTimestamp(), GetFlushRecPtr(), GetStandbyFlushRecPtr(), GetWALInsertionTimeLine(), got_STOPPING, LagTrackerWrite(), StringInfoData::len, list_free_deep(), LSN_FORMAT_ARGS, MAX_SEND_SIZE, memcpy(), MyWalSnd, output_message, pq_putmessage_noblock, pq_sendbyte(), pq_sendint64(), PqMsg_CopyData, PqMsg_CopyDone, PqReplMsg_WALData, readTimeLineHistory(), RecoveryInProgress(), resetStringInfo(), XLogReaderState::seg, XLogReaderState::segcxt, sendTimeLine, sendTimeLineIsHistoric, sendTimeLineNextTLI, sendTimeLineValidUpto, sentPtr, set_ps_display(), snprintf, SpinLockAcquire(), SpinLockRelease(), streamingDoneSending, tliSwitchPoint(), tmpbuf, update_process_title, wal_segment_close(), WALRead(), WALReadFromBuffers(), WALReadRaiseError(), WalSndCaughtUp, WalSndSetState(), WALSNDSTATE_STOPPING, WALOpenSegment::ws_file, WALSegmentContext::ws_segsize, WALOpenSegment::ws_tli, XLByteToSeg, and xlogreader.

Referenced by StartReplication().

Variable Documentation

am_cascading_walsender

bool am_cascading_walsender = false

Definition at line 136 of file walsender.c.

Referenced by GetStandbyFlushRecPtr(), IdentifySystem(), InitWalSender(), logical_read_xlog_page(), ProcessStandbyReplyMessage(), StartLogicalReplication(), StartReplication(), SyncRepGetStandbyPriority(), WalSndHandleConfigReload(), XLogSendLogical(), and XLogSendPhysical().

am_db_walsender

bool am_db_walsender = false

Definition at line 138 of file walsender.c.

Referenced by check_db(), ClientAuthentication(), InitPostgres(), and ProcessStartupPacket().

am_walsender

bool am_walsender = false

Definition at line 135 of file walsender.c.

Referenced by BackendInitialize(), check_db(), ClientAuthentication(), forbidden_in_wal_sender(), HandleWalSndInitStopping(), InitPostgres(), LagTrackerWrite(), MarkPostmasterChildWalSender(), PerformAuthentication(), PostgresMain(), ProcessStartupPacket(), ReplicationSlotAcquire(), ReplicationSlotRelease(), and WalSndSetState().

got_SIGUSR2

volatile sig_atomic_t got_SIGUSR2 = false

static

Definition at line 232 of file walsender.c.

Referenced by WalSndCheckShutdownTimeout(), WalSndErrorCleanup(), WalSndLastCycleHandler(), WalSndLoop(), and XLogSendLogical().

got_STOPPING

volatile sig_atomic_t got_STOPPING = false

static

Definition at line 233 of file walsender.c.

Referenced by exec_replication_command(), HandleWalSndInitStopping(), NeedToWaitForStandbys(), StartLogicalReplication(), StartReplication(), WalSndCheckShutdownTimeout(), WalSndErrorCleanup(), WalSndWaitForWal(), XLogSendLogical(), and XLogSendPhysical().

lag_tracker

LagTracker* lag_tracker

static

Definition at line 279 of file walsender.c.

Referenced by InitWalSender(), LagTrackerRead(), and LagTrackerWrite().

last_processing

TimestampTz last_processing = 0

static

Definition at line 198 of file walsender.c.

Referenced by ProcessRepliesIfAny(), WalSndCheckTimeOut(), and WalSndKeepaliveIfNecessary().

last_reply_timestamp

TimestampTz last_reply_timestamp = 0

static

Definition at line 204 of file walsender.c.

Referenced by CreateReplicationSlot(), ProcessRepliesIfAny(), WalSndCheckTimeOut(), WalSndComputeSleeptime(), WalSndDone(), WalSndKeepaliveIfNecessary(), WalSndLoop(), WalSndUpdateProgress(), and WalSndWriteData().

log_replication_commands

bool log_replication_commands = false

Definition at line 150 of file walsender.c.

Referenced by exec_replication_command(), ReplicationSlotAcquire(), and ReplicationSlotRelease().

logical_decoding_ctx

LogicalDecodingContext* logical_decoding_ctx = NULL

static

Definition at line 243 of file walsender.c.

Referenced by StartLogicalReplication(), and XLogSendLogical().

max_wal_senders

int max_wal_senders = 10

Definition at line 141 of file walsender.c.

Referenced by CheckRequiredParameterValues(), InitControlFile(), InitializeMaxBackends(), InitPostmasterChildSlots(), InitProcess(), InitWalSenderSlot(), pg_stat_get_wal_senders(), PostmasterMain(), SyncRepGetCandidateStandbys(), WalSndInitStopping(), WalSndRqstFileReload(), WalSndShmemInit(), WalSndShmemRequest(), WalSndWaitStopping(), WalSndWakeupProcessRequests(), and XLogReportParameters().

MyWalSnd

WalSnd* MyWalSnd = NULL

Definition at line 132 of file walsender.c.

Referenced by exec_replication_command(), InitWalSenderSlot(), ProcessStandbyHSFeedbackMessage(), ProcessStandbyPSRequestMessage(), ProcessStandbyReplyMessage(), StartLogicalReplication(), StartReplication(), SyncRepGetCandidateStandbys(), SyncRepInitConfig(), SyncRepReleaseWaiters(), WalSndDone(), WalSndDoneImmediate(), WalSndKill(), WalSndLoop(), WalSndSetState(), WalSndWait(), WalSndWaitForWal(), XLogSendLogical(), and XLogSendPhysical().

output_message

StringInfoData output_message

static

Definition at line 193 of file walsender.c.

Referenced by exec_replication_command(), ProcessStandbyPSRequestMessage(), WalSndKeepalive(), and XLogSendPhysical().

replication_active

volatile sig_atomic_t replication_active = false

static

Definition at line 241 of file walsender.c.

Referenced by HandleWalSndInitStopping(), NeedToWaitForStandbys(), StartLogicalReplication(), StartReplication(), and WalSndErrorCleanup().

reply_message

StringInfoData reply_message

static

Definition at line 194 of file walsender.c.

Referenced by exec_replication_command(), ProcessRepliesIfAny(), ProcessStandbyHSFeedbackMessage(), ProcessStandbyMessage(), ProcessStandbyPSRequestMessage(), and ProcessStandbyReplyMessage().

sendTimeLine

TimeLineID sendTimeLine = 0

static

Definition at line 181 of file walsender.c.

Referenced by logical_read_xlog_page(), StartReplication(), WalSndSegmentOpen(), and XLogSendPhysical().

sendTimeLineIsHistoric

bool sendTimeLineIsHistoric = false

static

Definition at line 183 of file walsender.c.

Referenced by logical_read_xlog_page(), StartReplication(), WalSndSegmentOpen(), and XLogSendPhysical().

sendTimeLineNextTLI

TimeLineID sendTimeLineNextTLI = 0

static

Definition at line 182 of file walsender.c.

Referenced by logical_read_xlog_page(), StartReplication(), WalSndSegmentOpen(), and XLogSendPhysical().

sendTimeLineValidUpto

XLogRecPtr sendTimeLineValidUpto = InvalidXLogRecPtr

static

Definition at line 184 of file walsender.c.

Referenced by logical_read_xlog_page(), StartReplication(), WalSndSegmentOpen(), and XLogSendPhysical().

sentPtr

XLogRecPtr sentPtr = InvalidXLogRecPtr

static

Definition at line 190 of file walsender.c.

Referenced by ProcessStandbyReplyMessage(), StartLogicalReplication(), StartReplication(), WalSndDone(), WalSndKeepalive(), WalSndWaitForWal(), XLogSendLogical(), and XLogSendPhysical().

shutdown_request_timestamp

TimestampTz shutdown_request_timestamp = 0

static

Definition at line 210 of file walsender.c.

Referenced by WalSndCheckShutdownTimeout(), and WalSndComputeSleeptime().

shutdown_stream_done_queued

bool shutdown_stream_done_queued = false

static

Definition at line 217 of file walsender.c.

Referenced by WalSndDone(), and WalSndDoneImmediate().

streamingDoneReceiving

bool streamingDoneReceiving

static

Definition at line 226 of file walsender.c.

Referenced by ProcessRepliesIfAny(), StartReplication(), WalSndLoop(), and WalSndWaitForWal().

streamingDoneSending

bool streamingDoneSending

static

Definition at line 225 of file walsender.c.

Referenced by ProcessRepliesIfAny(), StartReplication(), WalSndLoop(), WalSndWaitForWal(), and XLogSendPhysical().

tmpbuf

StringInfoData tmpbuf

static

Definition at line 195 of file walsender.c.

Referenced by copy_crlf(), describeOneTableDetails(), exec_replication_command(), GetVisibilityMapPins(), mdc_finish(), multirange_recv(), parse_literal_data(), parse_symenc_sesskey(), pqGetHomeDirectory(), PQunescapeBytea(), prefix_init(), pullf_read_max(), scanGetCandidate(), shm_mq_sendv(), tsvectorin(), WalSndWriteData(), and XLogSendPhysical().

uploaded_manifest

IncrementalBackupInfo* uploaded_manifest = NULL

static

Definition at line 172 of file walsender.c.

Referenced by exec_replication_command(), and UploadManifest().

uploaded_manifest_mcxt

MemoryContext uploaded_manifest_mcxt = NULL

static

Definition at line 173 of file walsender.c.

Referenced by UploadManifest().

waiting_for_ping_response

bool waiting_for_ping_response = false

static

Definition at line 207 of file walsender.c.

Referenced by ProcessRepliesIfAny(), WalSndComputeSleeptime(), WalSndDone(), WalSndKeepalive(), WalSndKeepaliveIfNecessary(), WalSndLoop(), and WalSndWaitForWal().

wake_wal_senders

bool wake_wal_senders = false

Definition at line 155 of file walsender.c.

Referenced by WalSndWakeupProcessRequests().

wal_sender_shutdown_timeout

int wal_sender_shutdown_timeout = -1

Definition at line 146 of file walsender.c.

Referenced by WalSndCheckShutdownTimeout(), and WalSndComputeSleeptime().

wal_sender_timeout

int wal_sender_timeout = 60 * 1000

Definition at line 143 of file walsender.c.

Referenced by WalSndCheckTimeOut(), WalSndComputeSleeptime(), WalSndKeepaliveIfNecessary(), WalSndUpdateProgress(), and WalSndWriteData().

WalSndCaughtUp

bool WalSndCaughtUp = false

static

Definition at line 229 of file walsender.c.

Referenced by WalSndDone(), WalSndLoop(), WalSndWaitForWal(), XLogSendLogical(), and XLogSendPhysical().

WalSndCtl

WalSndCtlData* WalSndCtl = NULL

Definition at line 121 of file walsender.c.

Referenced by InitWalSenderSlot(), pg_stat_get_wal_senders(), PhysicalWakeupLogicalWalSnd(), SyncRepGetCandidateStandbys(), SyncRepQueueInsert(), SyncRepReleaseWaiters(), SyncRepUpdateSyncStandbysDefined(), SyncRepWaitForLSN(), SyncRepWakeQueue(), WaitForStandbyConfirmation(), WalSndInitStopping(), WalSndRqstFileReload(), WalSndShmemInit(), WalSndShmemRequest(), WalSndUpdateProgress(), WalSndWait(), WalSndWaitStopping(), and WalSndWakeup().

WalSndShmemCallbacks

const ShmemCallbacks WalSndShmemCallbacks

Initial value:

= {
    .request_fn = WalSndShmemRequest,
    .init_fn = WalSndShmemInit,
}

Definition at line 126 of file walsender.c.

                                            {
    .request_fn = WalSndShmemRequest,
    .init_fn = WalSndShmemInit,
};

xlogreader

XLogReaderState* xlogreader = NULL

static

Definition at line 162 of file walsender.c.

Referenced by exec_replication_command(), StartLogicalReplication(), StartReplication(), WalSndErrorCleanup(), and XLogSendPhysical().