launcher.c File Reference

#include "postgres.h"
#include "access/heapam.h"
#include "access/htup.h"
#include "access/htup_details.h"
#include "access/tableam.h"
#include "access/xact.h"
#include "catalog/pg_subscription.h"
#include "catalog/pg_subscription_rel.h"
#include "funcapi.h"
#include "libpq/pqsignal.h"
#include "miscadmin.h"
#include "pgstat.h"
#include "postmaster/bgworker.h"
#include "postmaster/fork_process.h"
#include "postmaster/interrupt.h"
#include "postmaster/postmaster.h"
#include "replication/logicallauncher.h"
#include "replication/logicalworker.h"
#include "replication/slot.h"
#include "replication/walreceiver.h"
#include "replication/worker_internal.h"
#include "storage/ipc.h"
#include "storage/proc.h"
#include "storage/procarray.h"
#include "storage/procsignal.h"
#include "tcop/tcopprot.h"
#include "utils/memutils.h"
#include "utils/pg_lsn.h"
#include "utils/ps_status.h"
#include "utils/snapmgr.h"
#include "utils/timeout.h"

Include dependency graph for launcher.c:

Go to the source code of this file.

Data Structures
struct	LogicalRepCtxStruct

Macros
#define	DEFAULT_NAPTIME_PER_CYCLE   180000L
#define	PG_STAT_GET_SUBSCRIPTION_COLS   8

Typedefs
typedef struct LogicalRepCtxStruct	LogicalRepCtxStruct

Functions
static void	ApplyLauncherWakeup (void)
static void	logicalrep_launcher_onexit (int code, Datum arg)
static void	logicalrep_worker_onexit (int code, Datum arg)
static void	logicalrep_worker_detach (void)
static void	logicalrep_worker_cleanup (LogicalRepWorker *worker)
Datum	pg_stat_get_subscription (PG_FUNCTION_ARGS)
static List *	get_subscription_list (void)
static void	WaitForReplicationWorkerAttach (LogicalRepWorker *worker, uint16 generation, BackgroundWorkerHandle *handle)
LogicalRepWorker *	logicalrep_worker_find (Oid subid, Oid relid, bool only_running)
List *	logicalrep_workers_find (Oid subid, bool only_running)
void	logicalrep_worker_launch (Oid dbid, Oid subid, const char *subname, Oid userid, Oid relid)
void	logicalrep_worker_stop (Oid subid, Oid relid)
void	logicalrep_worker_wakeup (Oid subid, Oid relid)
void	logicalrep_worker_wakeup_ptr (LogicalRepWorker *worker)
void	logicalrep_worker_attach (int slot)
int	logicalrep_sync_worker_count (Oid subid)
Size	ApplyLauncherShmemSize (void)
void	ApplyLauncherRegister (void)
void	ApplyLauncherShmemInit (void)
void	AtEOXact_ApplyLauncher (bool isCommit)
void	ApplyLauncherWakeupAtCommit (void)
void	ApplyLauncherMain (Datum main_arg)
bool	IsLogicalLauncher (void)

Variables
int	max_logical_replication_workers = 4
int	max_sync_workers_per_subscription = 2
LogicalRepWorker *	MyLogicalRepWorker = NULL
LogicalRepCtxStruct *	LogicalRepCtx
static bool	on_commit_launcher_wakeup = false

Macro Definition Documentation

DEFAULT_NAPTIME_PER_CYCLE

#define DEFAULT_NAPTIME_PER_CYCLE   180000L

Definition at line 52 of file launcher.c.

Referenced by ApplyLauncherMain().

PG_STAT_GET_SUBSCRIPTION_COLS

#define PG_STAT_GET_SUBSCRIPTION_COLS   8

Referenced by pg_stat_get_subscription().

Typedef Documentation

LogicalRepCtxStruct

typedef struct LogicalRepCtxStruct LogicalRepCtxStruct

Function Documentation

ApplyLauncherMain()

void ApplyLauncherMain

(

Datum

main_arg

)

Definition at line 797 of file launcher.c.

References ALLOCSET_DEFAULT_SIZES, AllocSetContextCreate, Assert, BackgroundWorkerInitializeConnection(), BackgroundWorkerUnblockSignals(), before_shmem_exit(), CHECK_FOR_INTERRUPTS, ConfigReloadPending, Subscription::dbid, DEBUG1, DEFAULT_NAPTIME_PER_CYCLE, die, Subscription::enabled, ereport, errmsg_internal(), get_subscription_list(), GetCurrentTimestamp(), InvalidOid, LogicalRepCtxStruct::launcher_pid, lfirst, logicalrep_launcher_onexit(), logicalrep_worker_find(), logicalrep_worker_launch(), LW_SHARED, LWLockAcquire(), LWLockRelease(), MemoryContextDelete(), MemoryContextSwitchTo(), MyLatch, MyProcPid, Subscription::name, now(), Subscription::oid, Subscription::owner, PGC_SIGHUP, pqsignal(), ProcessConfigFile(), ResetLatch(), SIGHUP, SignalHandlerForConfigReload(), TimestampDifferenceExceeds(), TopMemoryContext, WAIT_EVENT_LOGICAL_LAUNCHER_MAIN, WaitLatch(), wal_retrieve_retry_interval, WL_EXIT_ON_PM_DEATH, WL_LATCH_SET, and WL_TIMEOUT.

{
    TimestampTz last_start_time = 0;

    ereport(DEBUG1,
            (errmsg_internal("logical replication launcher started")));

    before_shmem_exit(logicalrep_launcher_onexit, (Datum) 0);

    Assert(LogicalRepCtx->launcher_pid == 0);
    LogicalRepCtx->launcher_pid = MyProcPid;

    /* Establish signal handlers. */
    pqsignal(SIGHUP, SignalHandlerForConfigReload);
    pqsignal(SIGTERM, die);
    BackgroundWorkerUnblockSignals();

    /*
     * Establish connection to nailed catalogs (we only ever access
     * pg_subscription).
     */
    BackgroundWorkerInitializeConnection(NULL, NULL, 0);

    /* Enter main loop */
    for (;;)
    {
        int         rc;
        List       *sublist;
        ListCell   *lc;
        MemoryContext subctx;
        MemoryContext oldctx;
        TimestampTz now;
        long        wait_time = DEFAULT_NAPTIME_PER_CYCLE;

        CHECK_FOR_INTERRUPTS();

        now = GetCurrentTimestamp();

        /* Limit the start retry to once a wal_retrieve_retry_interval */
        if (TimestampDifferenceExceeds(last_start_time, now,
                                       wal_retrieve_retry_interval))
        {
            /* Use temporary context for the database list and worker info. */
            subctx = AllocSetContextCreate(TopMemoryContext,
                                           "Logical Replication Launcher sublist",
                                           ALLOCSET_DEFAULT_SIZES);
            oldctx = MemoryContextSwitchTo(subctx);

            /* search for subscriptions to start or stop. */
            sublist = get_subscription_list();

            /* Start the missing workers for enabled subscriptions. */
            foreach(lc, sublist)
            {
                Subscription *sub = (Subscription *) lfirst(lc);
                LogicalRepWorker *w;

                if (!sub->enabled)
                    continue;

                LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
                w = logicalrep_worker_find(sub->oid, InvalidOid, false);
                LWLockRelease(LogicalRepWorkerLock);

                if (w == NULL)
                {
                    last_start_time = now;
                    wait_time = wal_retrieve_retry_interval;

                    logicalrep_worker_launch(sub->dbid, sub->oid, sub->name,
                                             sub->owner, InvalidOid);
                }
            }

            /* Switch back to original memory context. */
            MemoryContextSwitchTo(oldctx);
            /* Clean the temporary memory. */
            MemoryContextDelete(subctx);
        }
        else
        {
            /*
             * The wait in previous cycle was interrupted in less than
             * wal_retrieve_retry_interval since last worker was started, this
             * usually means crash of the worker, so we should retry in
             * wal_retrieve_retry_interval again.
             */
            wait_time = wal_retrieve_retry_interval;
        }

        /* Wait for more work. */
        rc = WaitLatch(MyLatch,
                       WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
                       wait_time,
                       WAIT_EVENT_LOGICAL_LAUNCHER_MAIN);

        if (rc & WL_LATCH_SET)
        {
            ResetLatch(MyLatch);
            CHECK_FOR_INTERRUPTS();
        }

        if (ConfigReloadPending)
        {
            ConfigReloadPending = false;
            ProcessConfigFile(PGC_SIGHUP);
        }
    }

    /* Not reachable */
}

ApplyLauncherRegister()

void ApplyLauncherRegister

(

void

)

Definition at line 702 of file launcher.c.

References BackgroundWorker::bgw_flags, BackgroundWorker::bgw_function_name, BackgroundWorker::bgw_library_name, BackgroundWorker::bgw_main_arg, BGW_MAXLEN, BackgroundWorker::bgw_name, BackgroundWorker::bgw_notify_pid, BackgroundWorker::bgw_restart_time, BackgroundWorker::bgw_start_time, BackgroundWorker::bgw_type, BGWORKER_BACKEND_DATABASE_CONNECTION, BGWORKER_SHMEM_ACCESS, BgWorkerStart_RecoveryFinished, max_logical_replication_workers, RegisterBackgroundWorker(), and snprintf.

Referenced by PostmasterMain().

{
    BackgroundWorker bgw;

    if (max_logical_replication_workers == 0)
        return;

    memset(&bgw, 0, sizeof(bgw));
    bgw.bgw_flags = BGWORKER_SHMEM_ACCESS |
        BGWORKER_BACKEND_DATABASE_CONNECTION;
    bgw.bgw_start_time = BgWorkerStart_RecoveryFinished;
    snprintf(bgw.bgw_library_name, BGW_MAXLEN, "postgres");
    snprintf(bgw.bgw_function_name, BGW_MAXLEN, "ApplyLauncherMain");
    snprintf(bgw.bgw_name, BGW_MAXLEN,
             "logical replication launcher");
    snprintf(bgw.bgw_type, BGW_MAXLEN,
             "logical replication launcher");
    bgw.bgw_restart_time = 5;
    bgw.bgw_notify_pid = 0;
    bgw.bgw_main_arg = (Datum) 0;

    RegisterBackgroundWorker(&bgw);
}

ApplyLauncherShmemInit()

void ApplyLauncherShmemInit

(

void

)

Definition at line 731 of file launcher.c.

References ApplyLauncherShmemSize(), max_logical_replication_workers, LogicalRepWorker::relmutex, ShmemInitStruct(), SpinLockInit, and LogicalRepCtxStruct::workers.

Referenced by CreateSharedMemoryAndSemaphores().

{
    bool        found;

    LogicalRepCtx = (LogicalRepCtxStruct *)
        ShmemInitStruct("Logical Replication Launcher Data",
                        ApplyLauncherShmemSize(),
                        &found);

    if (!found)
    {
        int         slot;

        memset(LogicalRepCtx, 0, ApplyLauncherShmemSize());

        /* Initialize memory and spin locks for each worker slot. */
        for (slot = 0; slot < max_logical_replication_workers; slot++)
        {
            LogicalRepWorker *worker = &LogicalRepCtx->workers[slot];

            memset(worker, 0, sizeof(LogicalRepWorker));
            SpinLockInit(&worker->relmutex);
        }
    }
}

ApplyLauncherShmemSize()

Size ApplyLauncherShmemSize

(

void

)

Definition at line 683 of file launcher.c.

References add_size(), max_logical_replication_workers, MAXALIGN, and mul_size().

Referenced by ApplyLauncherShmemInit(), and CreateSharedMemoryAndSemaphores().

{
    Size        size;

    /*
     * Need the fixed struct and the array of LogicalRepWorker.
     */
    size = sizeof(LogicalRepCtxStruct);
    size = MAXALIGN(size);
    size = add_size(size, mul_size(max_logical_replication_workers,
                                   sizeof(LogicalRepWorker)));
    return size;
}

ApplyLauncherWakeup()

static void ApplyLauncherWakeup ( void  )

static

Definition at line 787 of file launcher.c.

References kill, LogicalRepCtxStruct::launcher_pid, and SIGUSR1.

Referenced by AtEOXact_ApplyLauncher(), and logicalrep_worker_onexit().

{
    if (LogicalRepCtx->launcher_pid != 0)
        kill(LogicalRepCtx->launcher_pid, SIGUSR1);
}

ApplyLauncherWakeupAtCommit()

void ApplyLauncherWakeupAtCommit

(

void

)

Definition at line 780 of file launcher.c.

References on_commit_launcher_wakeup.

Referenced by AlterSubscription(), and CreateSubscription().

{
    if (!on_commit_launcher_wakeup)
        on_commit_launcher_wakeup = true;
}

AtEOXact_ApplyLauncher()

void AtEOXact_ApplyLauncher

(

bool

isCommit

)

Definition at line 761 of file launcher.c.

References ApplyLauncherWakeup(), and on_commit_launcher_wakeup.

Referenced by AbortTransaction(), and CommitTransaction().

{
    if (isCommit)
    {
        if (on_commit_launcher_wakeup)
            ApplyLauncherWakeup();
    }

    on_commit_launcher_wakeup = false;
}

get_subscription_list()

static List* get_subscription_list ( void  )

static

Definition at line 88 of file launcher.c.

References AccessShareLock, CommitTransactionCommand(), CurrentMemoryContext, Subscription::dbid, Subscription::enabled, ForwardScanDirection, GETSTRUCT, GetTransactionSnapshot(), heap_getnext(), HeapTupleIsValid, lappend(), MemoryContextSwitchTo(), Subscription::name, NameStr, NIL, Subscription::oid, Subscription::owner, palloc0(), pstrdup(), StartTransactionCommand(), table_beginscan_catalog(), table_close(), table_endscan(), and table_open().

Referenced by ApplyLauncherMain().

{
    List       *res = NIL;
    Relation    rel;
    TableScanDesc scan;
    HeapTuple   tup;
    MemoryContext resultcxt;

    /* This is the context that we will allocate our output data in */
    resultcxt = CurrentMemoryContext;

    /*
     * Start a transaction so we can access pg_database, and get a snapshot.
     * We don't have a use for the snapshot itself, but we're interested in
     * the secondary effect that it sets RecentGlobalXmin.  (This is critical
     * for anything that reads heap pages, because HOT may decide to prune
     * them even if the process doesn't attempt to modify any tuples.)
     *
     * FIXME: This comment is inaccurate / the code buggy. A snapshot that is
     * not pushed/active does not reliably prevent HOT pruning (->xmin could
     * e.g. be cleared when cache invalidations are processed).
     */
    StartTransactionCommand();
    (void) GetTransactionSnapshot();

    rel = table_open(SubscriptionRelationId, AccessShareLock);
    scan = table_beginscan_catalog(rel, 0, NULL);

    while (HeapTupleIsValid(tup = heap_getnext(scan, ForwardScanDirection)))
    {
        Form_pg_subscription subform = (Form_pg_subscription) GETSTRUCT(tup);
        Subscription *sub;
        MemoryContext oldcxt;

        /*
         * Allocate our results in the caller's context, not the
         * transaction's. We do this inside the loop, and restore the original
         * context at the end, so that leaky things like heap_getnext() are
         * not called in a potentially long-lived context.
         */
        oldcxt = MemoryContextSwitchTo(resultcxt);

        sub = (Subscription *) palloc0(sizeof(Subscription));
        sub->oid = subform->oid;
        sub->dbid = subform->subdbid;
        sub->owner = subform->subowner;
        sub->enabled = subform->subenabled;
        sub->name = pstrdup(NameStr(subform->subname));
        /* We don't fill fields we are not interested in. */

        res = lappend(res, sub);
        MemoryContextSwitchTo(oldcxt);
    }

    table_endscan(scan);
    table_close(rel, AccessShareLock);

    CommitTransactionCommand();

    return res;
}

IsLogicalLauncher()

bool IsLogicalLauncher

(

void

)

Definition at line 913 of file launcher.c.

References LogicalRepCtxStruct::launcher_pid, and MyProcPid.

Referenced by ProcessInterrupts().

{
    return LogicalRepCtx->launcher_pid == MyProcPid;
}

logicalrep_launcher_onexit()

static void logicalrep_launcher_onexit ( int  code, Datum  arg  )

static

Definition at line 632 of file launcher.c.

References LogicalRepCtxStruct::launcher_pid.

Referenced by ApplyLauncherMain().

{
    LogicalRepCtx->launcher_pid = 0;
}

logicalrep_sync_worker_count()

int logicalrep_sync_worker_count

(

Oid

subid

)

Definition at line 659 of file launcher.c.

References Assert, i, LWLockHeldByMe(), max_logical_replication_workers, OidIsValid, LogicalRepWorker::relid, LogicalRepWorker::subid, and LogicalRepCtxStruct::workers.

Referenced by logicalrep_worker_launch(), and process_syncing_tables_for_apply().

{
    int         i;
    int         res = 0;

    Assert(LWLockHeldByMe(LogicalRepWorkerLock));

    /* Search for attached worker for a given subscription id. */
    for (i = 0; i < max_logical_replication_workers; i++)
    {
        LogicalRepWorker *w = &LogicalRepCtx->workers[i];

        if (w->subid == subid && OidIsValid(w->relid))
            res++;
    }

    return res;
}

logicalrep_worker_attach()

void logicalrep_worker_attach

(

int

slot

)

Definition at line 564 of file launcher.c.

References Assert, before_shmem_exit(), ereport, errcode(), errmsg(), ERROR, LogicalRepWorker::in_use, logicalrep_worker_onexit(), LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), max_logical_replication_workers, MyProc, LogicalRepWorker::proc, and LogicalRepCtxStruct::workers.

Referenced by ApplyWorkerMain().

{
    /* Block concurrent access. */
    LWLockAcquire(LogicalRepWorkerLock, LW_EXCLUSIVE);

    Assert(slot >= 0 && slot < max_logical_replication_workers);
    MyLogicalRepWorker = &LogicalRepCtx->workers[slot];

    if (!MyLogicalRepWorker->in_use)
    {
        LWLockRelease(LogicalRepWorkerLock);
        ereport(ERROR,
                (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                 errmsg("logical replication worker slot %d is empty, cannot attach",
                        slot)));
    }

    if (MyLogicalRepWorker->proc)
    {
        LWLockRelease(LogicalRepWorkerLock);
        ereport(ERROR,
                (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                 errmsg("logical replication worker slot %d is already used by "
                        "another worker, cannot attach", slot)));
    }

    MyLogicalRepWorker->proc = MyProc;
    before_shmem_exit(logicalrep_worker_onexit, (Datum) 0);

    LWLockRelease(LogicalRepWorkerLock);
}

logicalrep_worker_cleanup()

static void logicalrep_worker_cleanup ( LogicalRepWorker *  worker )

static

Definition at line 614 of file launcher.c.

References Assert, LogicalRepWorker::dbid, LogicalRepWorker::in_use, InvalidOid, LW_EXCLUSIVE, LWLockHeldByMeInMode(), LogicalRepWorker::proc, LogicalRepWorker::relid, LogicalRepWorker::subid, and LogicalRepWorker::userid.

Referenced by logicalrep_worker_detach(), logicalrep_worker_launch(), and WaitForReplicationWorkerAttach().

{
    Assert(LWLockHeldByMeInMode(LogicalRepWorkerLock, LW_EXCLUSIVE));

    worker->in_use = false;
    worker->proc = NULL;
    worker->dbid = InvalidOid;
    worker->userid = InvalidOid;
    worker->subid = InvalidOid;
    worker->relid = InvalidOid;
}

logicalrep_worker_detach()

static void logicalrep_worker_detach ( void  )

static

Definition at line 600 of file launcher.c.

References logicalrep_worker_cleanup(), LW_EXCLUSIVE, LWLockAcquire(), and LWLockRelease().

Referenced by logicalrep_worker_onexit().

{
    /* Block concurrent access. */
    LWLockAcquire(LogicalRepWorkerLock, LW_EXCLUSIVE);

    logicalrep_worker_cleanup(MyLogicalRepWorker);

    LWLockRelease(LogicalRepWorkerLock);
}

logicalrep_worker_find()

LogicalRepWorker* logicalrep_worker_find	(	Oid	subid,
		Oid	relid,
		bool	only_running
	)

Definition at line 215 of file launcher.c.

References Assert, i, LogicalRepWorker::in_use, LWLockHeldByMe(), max_logical_replication_workers, LogicalRepWorker::proc, LogicalRepWorker::relid, LogicalRepWorker::subid, and LogicalRepCtxStruct::workers.

Referenced by ApplyLauncherMain(), logicalrep_worker_stop(), logicalrep_worker_wakeup(), process_syncing_tables_for_apply(), wait_for_relation_state_change(), and wait_for_worker_state_change().

{
    int         i;
    LogicalRepWorker *res = NULL;

    Assert(LWLockHeldByMe(LogicalRepWorkerLock));

    /* Search for attached worker for a given subscription id. */
    for (i = 0; i < max_logical_replication_workers; i++)
    {
        LogicalRepWorker *w = &LogicalRepCtx->workers[i];

        if (w->in_use && w->subid == subid && w->relid == relid &&
            (!only_running || w->proc))
        {
            res = w;
            break;
        }
    }

    return res;
}

logicalrep_worker_launch()

void logicalrep_worker_launch	(	Oid	dbid,
		Oid	subid,
		const char *	subname,
		Oid	userid,
		Oid	relid
	)

Definition at line 266 of file launcher.c.

References Assert, BackgroundWorker::bgw_flags, BackgroundWorker::bgw_function_name, BackgroundWorker::bgw_library_name, BackgroundWorker::bgw_main_arg, BGW_MAXLEN, BackgroundWorker::bgw_name, BGW_NEVER_RESTART, BackgroundWorker::bgw_notify_pid, BackgroundWorker::bgw_restart_time, BackgroundWorker::bgw_start_time, BackgroundWorker::bgw_type, BGWORKER_BACKEND_DATABASE_CONNECTION, BGWORKER_SHMEM_ACCESS, BgWorkerStart_RecoveryFinished, LogicalRepWorker::dbid, DEBUG1, elog, ereport, errcode(), errhint(), errmsg(), errmsg_internal(), ERROR, LogicalRepWorker::generation, GetCurrentTimestamp(), i, LogicalRepWorker::in_use, Int32GetDatum, InvalidXLogRecPtr, LogicalRepWorker::last_lsn, LogicalRepWorker::last_recv_time, LogicalRepWorker::last_send_time, LogicalRepWorker::launch_time, logicalrep_sync_worker_count(), logicalrep_worker_cleanup(), LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), max_logical_replication_workers, max_replication_slots, max_sync_workers_per_subscription, MyProcPid, now(), OidIsValid, LogicalRepWorker::proc, RegisterDynamicBackgroundWorker(), LogicalRepWorker::relid, LogicalRepWorker::relstate, LogicalRepWorker::relstate_lsn, LogicalRepWorker::reply_lsn, LogicalRepWorker::reply_time, snprintf, LogicalRepWorker::subid, TIMESTAMP_NOBEGIN, TimestampDifferenceExceeds(), LogicalRepWorker::userid, WaitForReplicationWorkerAttach(), wal_receiver_timeout, WARNING, and LogicalRepCtxStruct::workers.

Referenced by ApplyLauncherMain(), and process_syncing_tables_for_apply().

{
    BackgroundWorker bgw;
    BackgroundWorkerHandle *bgw_handle;
    uint16      generation;
    int         i;
    int         slot = 0;
    LogicalRepWorker *worker = NULL;
    int         nsyncworkers;
    TimestampTz now;

    ereport(DEBUG1,
            (errmsg_internal("starting logical replication worker for subscription \"%s\"",
                             subname)));

    /* Report this after the initial starting message for consistency. */
    if (max_replication_slots == 0)
        ereport(ERROR,
                (errcode(ERRCODE_CONFIGURATION_LIMIT_EXCEEDED),
                 errmsg("cannot start logical replication workers when max_replication_slots = 0")));

    /*
     * We need to do the modification of the shared memory under lock so that
     * we have consistent view.
     */
    LWLockAcquire(LogicalRepWorkerLock, LW_EXCLUSIVE);

retry:
    /* Find unused worker slot. */
    for (i = 0; i < max_logical_replication_workers; i++)
    {
        LogicalRepWorker *w = &LogicalRepCtx->workers[i];

        if (!w->in_use)
        {
            worker = w;
            slot = i;
            break;
        }
    }

    nsyncworkers = logicalrep_sync_worker_count(subid);

    now = GetCurrentTimestamp();

    /*
     * If we didn't find a free slot, try to do garbage collection.  The
     * reason we do this is because if some worker failed to start up and its
     * parent has crashed while waiting, the in_use state was never cleared.
     */
    if (worker == NULL || nsyncworkers >= max_sync_workers_per_subscription)
    {
        bool        did_cleanup = false;

        for (i = 0; i < max_logical_replication_workers; i++)
        {
            LogicalRepWorker *w = &LogicalRepCtx->workers[i];

            /*
             * If the worker was marked in use but didn't manage to attach in
             * time, clean it up.
             */
            if (w->in_use && !w->proc &&
                TimestampDifferenceExceeds(w->launch_time, now,
                                           wal_receiver_timeout))
            {
                elog(WARNING,
                     "logical replication worker for subscription %u took too long to start; canceled",
                     w->subid);

                logicalrep_worker_cleanup(w);
                did_cleanup = true;
            }
        }

        if (did_cleanup)
            goto retry;
    }

    /*
     * If we reached the sync worker limit per subscription, just exit
     * silently as we might get here because of an otherwise harmless race
     * condition.
     */
    if (nsyncworkers >= max_sync_workers_per_subscription)
    {
        LWLockRelease(LogicalRepWorkerLock);
        return;
    }

    /*
     * However if there are no more free worker slots, inform user about it
     * before exiting.
     */
    if (worker == NULL)
    {
        LWLockRelease(LogicalRepWorkerLock);
        ereport(WARNING,
                (errcode(ERRCODE_CONFIGURATION_LIMIT_EXCEEDED),
                 errmsg("out of logical replication worker slots"),
                 errhint("You might need to increase max_logical_replication_workers.")));
        return;
    }

    /* Prepare the worker slot. */
    worker->launch_time = now;
    worker->in_use = true;
    worker->generation++;
    worker->proc = NULL;
    worker->dbid = dbid;
    worker->userid = userid;
    worker->subid = subid;
    worker->relid = relid;
    worker->relstate = SUBREL_STATE_UNKNOWN;
    worker->relstate_lsn = InvalidXLogRecPtr;
    worker->last_lsn = InvalidXLogRecPtr;
    TIMESTAMP_NOBEGIN(worker->last_send_time);
    TIMESTAMP_NOBEGIN(worker->last_recv_time);
    worker->reply_lsn = InvalidXLogRecPtr;
    TIMESTAMP_NOBEGIN(worker->reply_time);

    /* Before releasing lock, remember generation for future identification. */
    generation = worker->generation;

    LWLockRelease(LogicalRepWorkerLock);

    /* Register the new dynamic worker. */
    memset(&bgw, 0, sizeof(bgw));
    bgw.bgw_flags = BGWORKER_SHMEM_ACCESS |
        BGWORKER_BACKEND_DATABASE_CONNECTION;
    bgw.bgw_start_time = BgWorkerStart_RecoveryFinished;
    snprintf(bgw.bgw_library_name, BGW_MAXLEN, "postgres");
    snprintf(bgw.bgw_function_name, BGW_MAXLEN, "ApplyWorkerMain");
    if (OidIsValid(relid))
        snprintf(bgw.bgw_name, BGW_MAXLEN,
                 "logical replication worker for subscription %u sync %u", subid, relid);
    else
        snprintf(bgw.bgw_name, BGW_MAXLEN,
                 "logical replication worker for subscription %u", subid);
    snprintf(bgw.bgw_type, BGW_MAXLEN, "logical replication worker");

    bgw.bgw_restart_time = BGW_NEVER_RESTART;
    bgw.bgw_notify_pid = MyProcPid;
    bgw.bgw_main_arg = Int32GetDatum(slot);

    if (!RegisterDynamicBackgroundWorker(&bgw, &bgw_handle))
    {
        /* Failed to start worker, so clean up the worker slot. */
        LWLockAcquire(LogicalRepWorkerLock, LW_EXCLUSIVE);
        Assert(generation == worker->generation);
        logicalrep_worker_cleanup(worker);
        LWLockRelease(LogicalRepWorkerLock);

        ereport(WARNING,
                (errcode(ERRCODE_CONFIGURATION_LIMIT_EXCEEDED),
                 errmsg("out of background worker slots"),
                 errhint("You might need to increase max_worker_processes.")));
        return;
    }

    /* Now wait until it attaches. */
    WaitForReplicationWorkerAttach(worker, generation, bgw_handle);
}

logicalrep_worker_onexit()

static void logicalrep_worker_onexit ( int  code, Datum  arg  )

static

Definition at line 643 of file launcher.c.

References ApplyLauncherWakeup(), logicalrep_worker_detach(), LogRepWorkerWalRcvConn, and walrcv_disconnect.

Referenced by logicalrep_worker_attach().

{
    /* Disconnect gracefully from the remote side. */
    if (LogRepWorkerWalRcvConn)
        walrcv_disconnect(LogRepWorkerWalRcvConn);

    logicalrep_worker_detach();

    ApplyLauncherWakeup();
}

logicalrep_worker_stop()

void logicalrep_worker_stop	(	Oid	subid,
		Oid	relid
	)

Definition at line 436 of file launcher.c.

References CHECK_FOR_INTERRUPTS, LogicalRepWorker::generation, LogicalRepWorker::in_use, kill, logicalrep_worker_find(), LW_SHARED, LWLockAcquire(), LWLockRelease(), MyLatch, PGPROC::pid, LogicalRepWorker::proc, ResetLatch(), WAIT_EVENT_BGWORKER_SHUTDOWN, WAIT_EVENT_BGWORKER_STARTUP, WaitLatch(), WL_EXIT_ON_PM_DEATH, WL_LATCH_SET, and WL_TIMEOUT.

Referenced by AlterSubscription_refresh(), and DropSubscription().

{
    LogicalRepWorker *worker;
    uint16      generation;

    LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);

    worker = logicalrep_worker_find(subid, relid, false);

    /* No worker, nothing to do. */
    if (!worker)
    {
        LWLockRelease(LogicalRepWorkerLock);
        return;
    }

    /*
     * Remember which generation was our worker so we can check if what we see
     * is still the same one.
     */
    generation = worker->generation;

    /*
     * If we found a worker but it does not have proc set then it is still
     * starting up; wait for it to finish starting and then kill it.
     */
    while (worker->in_use && !worker->proc)
    {
        int         rc;

        LWLockRelease(LogicalRepWorkerLock);

        /* Wait a bit --- we don't expect to have to wait long. */
        rc = WaitLatch(MyLatch,
                       WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
                       10L, WAIT_EVENT_BGWORKER_STARTUP);

        if (rc & WL_LATCH_SET)
        {
            ResetLatch(MyLatch);
            CHECK_FOR_INTERRUPTS();
        }

        /* Recheck worker status. */
        LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);

        /*
         * Check whether the worker slot is no longer used, which would mean
         * that the worker has exited, or whether the worker generation is
         * different, meaning that a different worker has taken the slot.
         */
        if (!worker->in_use || worker->generation != generation)
        {
            LWLockRelease(LogicalRepWorkerLock);
            return;
        }

        /* Worker has assigned proc, so it has started. */
        if (worker->proc)
            break;
    }

    /* Now terminate the worker ... */
    kill(worker->proc->pid, SIGTERM);

    /* ... and wait for it to die. */
    for (;;)
    {
        int         rc;

        /* is it gone? */
        if (!worker->proc || worker->generation != generation)
            break;

        LWLockRelease(LogicalRepWorkerLock);

        /* Wait a bit --- we don't expect to have to wait long. */
        rc = WaitLatch(MyLatch,
                       WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
                       10L, WAIT_EVENT_BGWORKER_SHUTDOWN);

        if (rc & WL_LATCH_SET)
        {
            ResetLatch(MyLatch);
            CHECK_FOR_INTERRUPTS();
        }

        LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
    }

    LWLockRelease(LogicalRepWorkerLock);
}

logicalrep_worker_wakeup()

void logicalrep_worker_wakeup	(	Oid	subid,
		Oid	relid
	)

Definition at line 533 of file launcher.c.

References logicalrep_worker_find(), logicalrep_worker_wakeup_ptr(), LW_SHARED, LWLockAcquire(), and LWLockRelease().

Referenced by pg_attribute_noreturn().

{
    LogicalRepWorker *worker;

    LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);

    worker = logicalrep_worker_find(subid, relid, true);

    if (worker)
        logicalrep_worker_wakeup_ptr(worker);

    LWLockRelease(LogicalRepWorkerLock);
}

logicalrep_worker_wakeup_ptr()

void logicalrep_worker_wakeup_ptr

(

LogicalRepWorker *

worker

)

Definition at line 553 of file launcher.c.

References Assert, LWLockHeldByMe(), LogicalRepWorker::proc, PGPROC::procLatch, and SetLatch().

Referenced by logicalrep_worker_wakeup(), process_syncing_tables_for_apply(), and wait_for_worker_state_change().

{
    Assert(LWLockHeldByMe(LogicalRepWorkerLock));

    SetLatch(&worker->proc->procLatch);
}

logicalrep_workers_find()

List* logicalrep_workers_find	(	Oid	subid,
		bool	only_running
	)

Definition at line 243 of file launcher.c.

References Assert, i, LogicalRepWorker::in_use, lappend(), LWLockHeldByMe(), max_logical_replication_workers, NIL, LogicalRepWorker::proc, LogicalRepWorker::subid, and LogicalRepCtxStruct::workers.

Referenced by DropSubscription().

{
    int         i;
    List       *res = NIL;

    Assert(LWLockHeldByMe(LogicalRepWorkerLock));

    /* Search for attached worker for a given subscription id. */
    for (i = 0; i < max_logical_replication_workers; i++)
    {
        LogicalRepWorker *w = &LogicalRepCtx->workers[i];

        if (w->in_use && w->subid == subid && (!only_running || w->proc))
            res = lappend(res, w);
    }

    return res;
}

pg_stat_get_subscription()

Datum pg_stat_get_subscription

(

PG_FUNCTION_ARGS

)

Definition at line 922 of file launcher.c.

References ReturnSetInfo::allowedModes, ReturnSetInfo::econtext, ExprContext::ecxt_per_query_memory, elog, ereport, errcode(), errmsg(), ERROR, get_call_result_type(), i, Int32GetDatum, InvalidOid, IsA, IsBackendPid(), LogicalRepWorker::last_lsn, LogicalRepWorker::last_recv_time, LogicalRepWorker::last_send_time, LSNGetDatum, LW_SHARED, LWLockAcquire(), LWLockRelease(), max_logical_replication_workers, MemoryContextSwitchTo(), MemSet, ObjectIdGetDatum, OidIsValid, PG_ARGISNULL, PG_GETARG_OID, PG_STAT_GET_SUBSCRIPTION_COLS, PGPROC::pid, LogicalRepWorker::proc, LogicalRepWorker::relid, LogicalRepWorker::reply_lsn, LogicalRepWorker::reply_time, ReturnSetInfo::returnMode, ReturnSetInfo::setDesc, ReturnSetInfo::setResult, SFRM_Materialize, LogicalRepWorker::subid, TimestampTzGetDatum, tuplestore_begin_heap(), tuplestore_donestoring, tuplestore_putvalues(), TYPEFUNC_COMPOSITE, values, work_mem, LogicalRepCtxStruct::workers, and XLogRecPtrIsInvalid.

{
#define PG_STAT_GET_SUBSCRIPTION_COLS   8
    Oid         subid = PG_ARGISNULL(0) ? InvalidOid : PG_GETARG_OID(0);
    int         i;
    ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
    TupleDesc   tupdesc;
    Tuplestorestate *tupstore;
    MemoryContext per_query_ctx;
    MemoryContext oldcontext;

    /* check to see if caller supports us returning a tuplestore */
    if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("set-valued function called in context that cannot accept a set")));
    if (!(rsinfo->allowedModes & SFRM_Materialize))
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("materialize mode required, but it is not allowed in this context")));

    /* Build a tuple descriptor for our result type */
    if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
        elog(ERROR, "return type must be a row type");

    per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
    oldcontext = MemoryContextSwitchTo(per_query_ctx);

    tupstore = tuplestore_begin_heap(true, false, work_mem);
    rsinfo->returnMode = SFRM_Materialize;
    rsinfo->setResult = tupstore;
    rsinfo->setDesc = tupdesc;

    MemoryContextSwitchTo(oldcontext);

    /* Make sure we get consistent view of the workers. */
    LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);

    for (i = 0; i <= max_logical_replication_workers; i++)
    {
        /* for each row */
        Datum       values[PG_STAT_GET_SUBSCRIPTION_COLS];
        bool        nulls[PG_STAT_GET_SUBSCRIPTION_COLS];
        int         worker_pid;
        LogicalRepWorker worker;

        memcpy(&worker, &LogicalRepCtx->workers[i],
               sizeof(LogicalRepWorker));
        if (!worker.proc || !IsBackendPid(worker.proc->pid))
            continue;

        if (OidIsValid(subid) && worker.subid != subid)
            continue;

        worker_pid = worker.proc->pid;

        MemSet(values, 0, sizeof(values));
        MemSet(nulls, 0, sizeof(nulls));

        values[0] = ObjectIdGetDatum(worker.subid);
        if (OidIsValid(worker.relid))
            values[1] = ObjectIdGetDatum(worker.relid);
        else
            nulls[1] = true;
        values[2] = Int32GetDatum(worker_pid);
        if (XLogRecPtrIsInvalid(worker.last_lsn))
            nulls[3] = true;
        else
            values[3] = LSNGetDatum(worker.last_lsn);
        if (worker.last_send_time == 0)
            nulls[4] = true;
        else
            values[4] = TimestampTzGetDatum(worker.last_send_time);
        if (worker.last_recv_time == 0)
            nulls[5] = true;
        else
            values[5] = TimestampTzGetDatum(worker.last_recv_time);
        if (XLogRecPtrIsInvalid(worker.reply_lsn))
            nulls[6] = true;
        else
            values[6] = LSNGetDatum(worker.reply_lsn);
        if (worker.reply_time == 0)
            nulls[7] = true;
        else
            values[7] = TimestampTzGetDatum(worker.reply_time);

        tuplestore_putvalues(tupstore, tupdesc, values, nulls);

        /*
         * If only a single subscription was requested, and we found it,
         * break.
         */
        if (OidIsValid(subid))
            break;
    }

    LWLockRelease(LogicalRepWorkerLock);

    /* clean up and return the tuplestore */
    tuplestore_donestoring(tupstore);

    return (Datum) 0;
}

WaitForReplicationWorkerAttach()

static void WaitForReplicationWorkerAttach ( LogicalRepWorker *  worker, uint16  generation, BackgroundWorkerHandle *  handle  )

static

Definition at line 157 of file launcher.c.

References BGWH_STOPPED, CHECK_FOR_INTERRUPTS, LogicalRepWorker::generation, GetBackgroundWorkerPid(), LogicalRepWorker::in_use, logicalrep_worker_cleanup(), LW_EXCLUSIVE, LW_SHARED, LWLockAcquire(), LWLockRelease(), MyLatch, LogicalRepWorker::proc, ResetLatch(), status(), WAIT_EVENT_BGWORKER_STARTUP, WaitLatch(), WL_EXIT_ON_PM_DEATH, WL_LATCH_SET, and WL_TIMEOUT.

Referenced by logicalrep_worker_launch().

{
    BgwHandleStatus status;
    int         rc;

    for (;;)
    {
        pid_t       pid;

        CHECK_FOR_INTERRUPTS();

        LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);

        /* Worker either died or has started; no need to do anything. */
        if (!worker->in_use || worker->proc)
        {
            LWLockRelease(LogicalRepWorkerLock);
            return;
        }

        LWLockRelease(LogicalRepWorkerLock);

        /* Check if worker has died before attaching, and clean up after it. */
        status = GetBackgroundWorkerPid(handle, &pid);

        if (status == BGWH_STOPPED)
        {
            LWLockAcquire(LogicalRepWorkerLock, LW_EXCLUSIVE);
            /* Ensure that this was indeed the worker we waited for. */
            if (generation == worker->generation)
                logicalrep_worker_cleanup(worker);
            LWLockRelease(LogicalRepWorkerLock);
            return;
        }

        /*
         * We need timeout because we generally don't get notified via latch
         * about the worker attach.  But we don't expect to have to wait long.
         */
        rc = WaitLatch(MyLatch,
                       WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
                       10L, WAIT_EVENT_BGWORKER_STARTUP);

        if (rc & WL_LATCH_SET)
        {
            ResetLatch(MyLatch);
            CHECK_FOR_INTERRUPTS();
        }
    }
}

Variable Documentation

LogicalRepCtx

LogicalRepCtxStruct* LogicalRepCtx

Definition at line 68 of file launcher.c.

max_logical_replication_workers

int max_logical_replication_workers = 4

Definition at line 54 of file launcher.c.

Referenced by ApplyLauncherRegister(), ApplyLauncherShmemInit(), ApplyLauncherShmemSize(), logicalrep_sync_worker_count(), logicalrep_worker_attach(), logicalrep_worker_find(), logicalrep_worker_launch(), logicalrep_workers_find(), and pg_stat_get_subscription().

max_sync_workers_per_subscription

int max_sync_workers_per_subscription = 2

Definition at line 55 of file launcher.c.

Referenced by logicalrep_worker_launch(), and process_syncing_tables_for_apply().

MyLogicalRepWorker

LogicalRepWorker* MyLogicalRepWorker = NULL

Definition at line 57 of file launcher.c.

Referenced by apply_handle_stream_abort(), apply_handle_stream_commit(), apply_handle_stream_start(), apply_handle_stream_stop(), apply_spooled_messages(), ApplyWorkerMain(), IsLogicalWorker(), LogicalRepSyncTableStart(), maybe_reread_subscription(), pg_attribute_noreturn(), process_syncing_tables_for_apply(), process_syncing_tables_for_sync(), should_apply_changes_for_rel(), UpdateWorkerStats(), wait_for_relation_state_change(), and wait_for_worker_state_change().

on_commit_launcher_wakeup

bool on_commit_launcher_wakeup = false

static

Definition at line 76 of file launcher.c.

Referenced by ApplyLauncherWakeupAtCommit(), and AtEOXact_ApplyLauncher().