walsender.h File Reference

#include <signal.h>

Include dependency graph for walsender.h:

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Macros
#define	WalSndWakeupRequest()    do { wake_wal_senders = true; } while (0)
#define	WalSndWakeupProcessRequests()

Enumerations
enum	CRSSnapshotAction { CRS_EXPORT_SNAPSHOT , CRS_NOEXPORT_SNAPSHOT , CRS_USE_SNAPSHOT }

Functions
void	InitWalSender (void)
bool	exec_replication_command (const char *cmd_string)
void	WalSndErrorCleanup (void)
void	WalSndResourceCleanup (bool isCommit)
void	WalSndSignals (void)
Size	WalSndShmemSize (void)
void	WalSndShmemInit (void)
void	WalSndWakeup (void)
void	WalSndInitStopping (void)
void	WalSndWaitStopping (void)
void	HandleWalSndInitStopping (void)
void	WalSndRqstFileReload (void)

Variables
PGDLLIMPORT bool	am_walsender
PGDLLIMPORT bool	am_cascading_walsender
PGDLLIMPORT bool	am_db_walsender
PGDLLIMPORT bool	wake_wal_senders
PGDLLIMPORT int	max_wal_senders
PGDLLIMPORT int	wal_sender_timeout
PGDLLIMPORT bool	log_replication_commands

Macro Definition Documentation

WalSndWakeupProcessRequests

#define WalSndWakeupProcessRequests

(

)

Value:

    do                                      \
    {                                       \
        if (wake_wal_senders)               \
        {                                   \
            wake_wal_senders = false;       \
            if (max_wal_senders > 0)        \
                WalSndWakeup();             \
        }                                   \
    } while (0)

Definition at line 63 of file walsender.h.

WalSndWakeupRequest

#define WalSndWakeupRequest

(

)

do { wake_wal_senders = true; } while (0)

Definition at line 57 of file walsender.h.

Enumeration Type Documentation

CRSSnapshotAction

enum CRSSnapshotAction

Enumerator
CRS_EXPORT_SNAPSHOT
CRS_NOEXPORT_SNAPSHOT
CRS_USE_SNAPSHOT

Definition at line 20 of file walsender.h.

{
    CRS_EXPORT_SNAPSHOT,
    CRS_NOEXPORT_SNAPSHOT,
    CRS_USE_SNAPSHOT
} CRSSnapshotAction;

Function Documentation

exec_replication_command()

bool exec_replication_command

(

const char *

cmd_string

)

Definition at line 1669 of file walsender.c.

{
    int         parse_rc;
    Node       *cmd_node;
    const char *cmdtag;
    MemoryContext cmd_context;
    MemoryContext old_context;
 
    /*
     * 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.
     */
    cmd_context = AllocSetContextCreate(CurrentMemoryContext,
                                        "Replication command context",
                                        ALLOCSET_DEFAULT_SIZES);
    old_context = MemoryContextSwitchTo(cmd_context);
 
    replication_scanner_init(cmd_string);
 
    /*
     * Is it a WalSender command?
     */
    if (!replication_scanner_is_replication_command())
    {
        /* Nope; clean up and get out. */
        replication_scanner_finish();
 
        MemoryContextSwitchTo(old_context);
        MemoryContextDelete(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();
    if (parse_rc != 0)
        ereport(ERROR,
                (errcode(ERRCODE_SYNTAX_ERROR),
                 errmsg_internal("replication command parser returned %d",
                                 parse_rc)));
    replication_scanner_finish();
 
    cmd_node = replication_parse_result;
 
    /*
     * 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);
            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_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;
 
        default:
            elog(ERROR, "unrecognized replication command node tag: %u",
                 cmd_node->type);
    }
 
    /* done */
    MemoryContextSwitchTo(old_context);
    MemoryContextDelete(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, Assert(), CHECK_FOR_INTERRUPTS, CommitTransactionCommand(), CreateDestReceiver(), CreateReplicationSlot(), CurrentMemoryContext, DEBUG1, debug_query_string, generate_unaccent_rules::dest, DestRemoteSimple, DropReplicationSlot(), elog(), EndReplicationCommand(), ereport, errcode(), errmsg(), errmsg_internal(), ERROR, GetPGVariable(), got_STOPPING, IdentifySystem(), initStringInfo(), InvalidOid, IsAbortedTransactionBlockState(), StartReplicationCmd::kind, LOG, log_replication_commands, MemoryContextDelete(), MemoryContextSwitchTo(), MyDatabaseId, MyWalSnd, VariableShowStmt::name, output_message, pgstat_report_activity(), PreventInTransactionBlock(), ReadReplicationSlot(), REPLICATION_KIND_PHYSICAL, replication_parse_result, 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, Node::type, ReadReplicationSlotCmd::type, WalSndSetState(), WALSNDSTATE_STOPPING, and xlogreader.

Referenced by PostgresMain().

HandleWalSndInitStopping()

void HandleWalSndInitStopping

(

void

)

Definition at line 3199 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;
}

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

Referenced by procsignal_sigusr1_handler().

InitWalSender()

void InitWalSender

(

void

)

Referenced by PostgresMain().

WalSndErrorCleanup()

void WalSndErrorCleanup

(

void

)

Definition at line 315 of file walsender.c.

{
    LWLockReleaseAll();
    ConditionVariableCancelSleep();
    pgstat_report_wait_end();
 
    if (xlogreader != NULL && xlogreader->seg.ws_file >= 0)
        wal_segment_close(xlogreader);
 
    if (MyReplicationSlot != NULL)
        ReplicationSlotRelease();
 
    ReplicationSlotCleanup();
 
    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())
        WalSndResourceCleanup(false);
 
    if (got_STOPPING || got_SIGUSR2)
        proc_exit(0);
 
    /* Revert back to startup state */
    WalSndSetState(WALSNDSTATE_STARTUP);
}

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

Referenced by PostgresMain().

WalSndInitStopping()

void WalSndInitStopping

(

void

)

Definition at line 3341 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, InvalidBackendId);
    }
}

References i, InvalidBackendId, max_wal_senders, WalSnd::mutex, WalSnd::pid, PROCSIG_WALSND_INIT_STOPPING, SendProcSignal(), SpinLockAcquire, SpinLockRelease, WalSndCtl, and WalSndCtlData::walsnds.

Referenced by ShutdownXLOG().

WalSndResourceCleanup()

void WalSndResourceCleanup

(

bool

isCommit

)

Definition at line 350 of file walsender.c.

{
    ResourceOwner resowner;
 
    if (CurrentResourceOwner == NULL)
        return;
 
    /*
     * Deleting CurrentResourceOwner is not allowed, so we must save a pointer
     * in a local variable and clear it first.
     */
    resowner = CurrentResourceOwner;
    CurrentResourceOwner = NULL;
 
    /* Now we can release resources and delete it. */
    ResourceOwnerRelease(resowner,
                         RESOURCE_RELEASE_BEFORE_LOCKS, isCommit, true);
    ResourceOwnerRelease(resowner,
                         RESOURCE_RELEASE_LOCKS, isCommit, true);
    ResourceOwnerRelease(resowner,
                         RESOURCE_RELEASE_AFTER_LOCKS, isCommit, true);
    ResourceOwnerDelete(resowner);
}

References CurrentResourceOwner, RESOURCE_RELEASE_AFTER_LOCKS, RESOURCE_RELEASE_BEFORE_LOCKS, RESOURCE_RELEASE_LOCKS, ResourceOwnerDelete(), and ResourceOwnerRelease().

Referenced by perform_base_backup(), and WalSndErrorCleanup().

WalSndRqstFileReload()

void WalSndRqstFileReload

(

void

)

Definition at line 3176 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 i, max_wal_senders, WalSnd::mutex, WalSnd::needreload, WalSnd::pid, SpinLockAcquire, SpinLockRelease, WalSndCtl, and WalSndCtlData::walsnds.

Referenced by KeepFileRestoredFromArchive().

WalSndShmemInit()

void WalSndShmemInit

(

void

)

Definition at line 3264 of file walsender.c.

{
    bool        found;
    int         i;
 
    WalSndCtl = (WalSndCtlData *)
        ShmemInitStruct("Wal Sender Ctl", WalSndShmemSize(), &found);
 
    if (!found)
    {
        /* First time through, so initialize */
        MemSet(WalSndCtl, 0, WalSndShmemSize());
 
        for (i = 0; i < NUM_SYNC_REP_WAIT_MODE; i++)
            dlist_init(&(WalSndCtl->SyncRepQueue[i]));
 
        for (i = 0; i < max_wal_senders; i++)
        {
            WalSnd     *walsnd = &WalSndCtl->walsnds[i];
 
            SpinLockInit(&walsnd->mutex);
        }
    }
}

References dlist_init(), i, max_wal_senders, MemSet, WalSnd::mutex, NUM_SYNC_REP_WAIT_MODE, ShmemInitStruct(), SpinLockInit, WalSndCtlData::SyncRepQueue, WalSndCtl, WalSndCtlData::walsnds, and WalSndShmemSize().

Referenced by CreateSharedMemoryAndSemaphores().

WalSndShmemSize()

Size WalSndShmemSize

(

void

)

Definition at line 3252 of file walsender.c.

{
    Size        size = 0;
 
    size = offsetof(WalSndCtlData, walsnds);
    size = add_size(size, mul_size(max_wal_senders, sizeof(WalSnd)));
 
    return size;
}

References add_size(), max_wal_senders, and mul_size().

Referenced by CalculateShmemSize(), and WalSndShmemInit().

WalSndSignals()

void WalSndSignals

(

void

)

Definition at line 3233 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, 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, SIG_DFL);
}

References die, InitializeTimeouts(), pqsignal(), procsignal_sigusr1_handler(), SIG_DFL, SIG_IGN, SIGCHLD, SIGHUP, SignalHandlerForConfigReload(), SIGPIPE, SIGUSR1, SIGUSR2, StatementCancelHandler(), and WalSndLastCycleHandler().

Referenced by PostgresMain().

WalSndWaitStopping()

void WalSndWaitStopping

(

void

)

Definition at line 3367 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 i, max_wal_senders, WalSnd::mutex, pg_usleep(), WalSnd::pid, SpinLockAcquire, SpinLockRelease, WalSnd::state, WalSndCtl, WalSndCtlData::walsnds, and WALSNDSTATE_STOPPING.

Referenced by ShutdownXLOG().

WalSndWakeup()

void WalSndWakeup

(

void

)

Definition at line 3296 of file walsender.c.

{
    int         i;
 
    for (i = 0; i < max_wal_senders; i++)
    {
        Latch      *latch;
        WalSnd     *walsnd = &WalSndCtl->walsnds[i];
 
        /*
         * Get latch pointer with spinlock held, for the unlikely case that
         * pointer reads aren't atomic (as they're 8 bytes).
         */
        SpinLockAcquire(&walsnd->mutex);
        latch = walsnd->latch;
        SpinLockRelease(&walsnd->mutex);
 
        if (latch != NULL)
            SetLatch(latch);
    }
}

References i, WalSnd::latch, max_wal_senders, WalSnd::mutex, SetLatch(), SpinLockAcquire, SpinLockRelease, WalSndCtl, and WalSndCtlData::walsnds.

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

Variable Documentation

am_cascading_walsender

PGDLLIMPORT bool am_cascading_walsender

extern

Definition at line 117 of file walsender.c.

Referenced by IdentifySystem(), ProcessStandbyReplyMessage(), StartLogicalReplication(), StartReplication(), SyncRepGetStandbyPriority(), and XLogSendPhysical().

am_db_walsender

PGDLLIMPORT bool am_db_walsender

extern

Definition at line 119 of file walsender.c.

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

am_walsender

PGDLLIMPORT bool am_walsender

extern

Definition at line 116 of file walsender.c.

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

log_replication_commands

PGDLLIMPORT bool log_replication_commands

extern

Definition at line 126 of file walsender.c.

Referenced by exec_replication_command().

max_wal_senders

PGDLLIMPORT int max_wal_senders

extern

Definition at line 122 of file walsender.c.

Referenced by check_autovacuum_max_workers(), check_max_connections(), check_max_worker_processes(), CheckRequiredParameterValues(), InitControlFile(), InitializeMaxBackends(), InitProcess(), InitWalSenderSlot(), MaxLivePostmasterChildren(), pg_stat_get_wal_senders(), PostmasterMain(), SyncRepGetCandidateStandbys(), WalSndInitStopping(), WalSndRqstFileReload(), WalSndShmemInit(), WalSndShmemSize(), WalSndWaitStopping(), WalSndWakeup(), and XLogReportParameters().

wake_wal_senders

PGDLLIMPORT bool wake_wal_senders

extern

Definition at line 131 of file walsender.c.

wal_sender_timeout

PGDLLIMPORT int wal_sender_timeout

extern

Definition at line 124 of file walsender.c.

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