startup.c

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/*-------------------------------------------------------------------------
 *
 * startup.c
 *
 * The Startup process initialises the server and performs any recovery
 * actions that have been specified. Notice that there is no "main loop"
 * since the Startup process ends as soon as initialisation is complete.
 * (in standby mode, one can think of the replay loop as a main loop,
 * though.)
 *
 *
 * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
 *
 *
 * IDENTIFICATION
 *    src/backend/postmaster/startup.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"
 
#include "access/xlog.h"
#include "access/xlogrecovery.h"
#include "access/xlogutils.h"
#include "libpq/pqsignal.h"
#include "miscadmin.h"
#include "pgstat.h"
#include "postmaster/interrupt.h"
#include "postmaster/startup.h"
#include "storage/ipc.h"
#include "storage/latch.h"
#include "storage/pmsignal.h"
#include "storage/procsignal.h"
#include "storage/standby.h"
#include "utils/guc.h"
#include "utils/memutils.h"
#include "utils/timeout.h"
 
 
#ifndef USE_POSTMASTER_DEATH_SIGNAL
/*
 * On systems that need to make a system call to find out if the postmaster has
 * gone away, we'll do so only every Nth call to HandleStartupProcInterrupts().
 * This only affects how long it takes us to detect the condition while we're
 * busy replaying WAL.  Latch waits and similar which should react immediately
 * through the usual techniques.
 */
#define POSTMASTER_POLL_RATE_LIMIT 1024
#endif
 
/*
 * Flags set by interrupt handlers for later service in the redo loop.
 */
static volatile sig_atomic_t got_SIGHUP = false;
static volatile sig_atomic_t shutdown_requested = false;
static volatile sig_atomic_t promote_signaled = false;
 
/*
 * Flag set when executing a restore command, to tell SIGTERM signal handler
 * that it's safe to just proc_exit.
 */
static volatile sig_atomic_t in_restore_command = false;
 
/*
 * Time at which the most recent startup operation started.
 */
static TimestampTz startup_progress_phase_start_time;
 
/*
 * Indicates whether the startup progress interval mentioned by the user is
 * elapsed or not. TRUE if timeout occurred, FALSE otherwise.
 */
static volatile sig_atomic_t startup_progress_timer_expired = false;
 
/*
 * Time between progress updates for long-running startup operations.
 */
int         log_startup_progress_interval = 10000;  /* 10 sec */
 
/* Signal handlers */
static void StartupProcTriggerHandler(SIGNAL_ARGS);
static void StartupProcSigHupHandler(SIGNAL_ARGS);
 
/* Callbacks */
static void StartupProcExit(int code, Datum arg);
 
 
/* --------------------------------
 *      signal handler routines
 * --------------------------------
 */
 
/* SIGUSR2: set flag to finish recovery */
static void
StartupProcTriggerHandler(SIGNAL_ARGS)
{
    int         save_errno = errno;
 
    promote_signaled = true;
    WakeupRecovery();
 
    errno = save_errno;
}
 
/* SIGHUP: set flag to re-read config file at next convenient time */
static void
StartupProcSigHupHandler(SIGNAL_ARGS)
{
    int         save_errno = errno;
 
    got_SIGHUP = true;
    WakeupRecovery();
 
    errno = save_errno;
}
 
/* SIGTERM: set flag to abort redo and exit */
static void
StartupProcShutdownHandler(SIGNAL_ARGS)
{
    int         save_errno = errno;
 
    if (in_restore_command)
        proc_exit(1);
    else
        shutdown_requested = true;
    WakeupRecovery();
 
    errno = save_errno;
}
 
/*
 * Re-read the config file.
 *
 * If one of the critical walreceiver options has changed, flag xlog.c
 * to restart it.
 */
static void
StartupRereadConfig(void)
{
    char       *conninfo = pstrdup(PrimaryConnInfo);
    char       *slotname = pstrdup(PrimarySlotName);
    bool        tempSlot = wal_receiver_create_temp_slot;
    bool        conninfoChanged;
    bool        slotnameChanged;
    bool        tempSlotChanged = false;
 
    ProcessConfigFile(PGC_SIGHUP);
 
    conninfoChanged = strcmp(conninfo, PrimaryConnInfo) != 0;
    slotnameChanged = strcmp(slotname, PrimarySlotName) != 0;
 
    /*
     * wal_receiver_create_temp_slot is used only when we have no slot
     * configured.  We do not need to track this change if it has no effect.
     */
    if (!slotnameChanged && strcmp(PrimarySlotName, "") == 0)
        tempSlotChanged = tempSlot != wal_receiver_create_temp_slot;
    pfree(conninfo);
    pfree(slotname);
 
    if (conninfoChanged || slotnameChanged || tempSlotChanged)
        StartupRequestWalReceiverRestart();
}
 
/* Handle various signals that might be sent to the startup process */
void
HandleStartupProcInterrupts(void)
{
#ifdef POSTMASTER_POLL_RATE_LIMIT
    static uint32 postmaster_poll_count = 0;
#endif
 
    /*
     * Process any requests or signals received recently.
     */
    if (got_SIGHUP)
    {
        got_SIGHUP = false;
        StartupRereadConfig();
    }
 
    /*
     * Check if we were requested to exit without finishing recovery.
     */
    if (shutdown_requested)
        proc_exit(1);
 
    /*
     * Emergency bailout if postmaster has died.  This is to avoid the
     * necessity for manual cleanup of all postmaster children.  Do this less
     * frequently on systems for which we don't have signals to make that
     * cheap.
     */
    if (IsUnderPostmaster &&
#ifdef POSTMASTER_POLL_RATE_LIMIT
        postmaster_poll_count++ % POSTMASTER_POLL_RATE_LIMIT == 0 &&
#endif
        !PostmasterIsAlive())
        exit(1);
 
    /* Process barrier events */
    if (ProcSignalBarrierPending)
        ProcessProcSignalBarrier();
 
    /* Perform logging of memory contexts of this process */
    if (LogMemoryContextPending)
        ProcessLogMemoryContextInterrupt();
}
 
 
/* --------------------------------
 *      signal handler routines
 * --------------------------------
 */
static void
StartupProcExit(int code, Datum arg)
{
    /* Shutdown the recovery environment */
    if (standbyState != STANDBY_DISABLED)
        ShutdownRecoveryTransactionEnvironment();
}
 
 
/* ----------------------------------
 *  Startup Process main entry point
 * ----------------------------------
 */
void
StartupProcessMain(void)
{
    /* Arrange to clean up at startup process exit */
    on_shmem_exit(StartupProcExit, 0);
 
    /*
     * Properly accept or ignore signals the postmaster might send us.
     */
    pqsignal(SIGHUP, StartupProcSigHupHandler); /* reload config file */
    pqsignal(SIGINT, SIG_IGN);  /* ignore query cancel */
    pqsignal(SIGTERM, StartupProcShutdownHandler);  /* 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, StartupProcTriggerHandler);
 
    /*
     * Reset some signals that are accepted by postmaster but not here
     */
    pqsignal(SIGCHLD, SIG_DFL);
 
    /*
     * Register timeouts needed for standby mode
     */
    RegisterTimeout(STANDBY_DEADLOCK_TIMEOUT, StandbyDeadLockHandler);
    RegisterTimeout(STANDBY_TIMEOUT, StandbyTimeoutHandler);
    RegisterTimeout(STANDBY_LOCK_TIMEOUT, StandbyLockTimeoutHandler);
 
    /*
     * Unblock signals (they were blocked when the postmaster forked us)
     */
    sigprocmask(SIG_SETMASK, &UnBlockSig, NULL);
 
    /*
     * Do what we came for.
     */
    StartupXLOG();
 
    /*
     * Exit normally. Exit code 0 tells postmaster that we completed recovery
     * successfully.
     */
    proc_exit(0);
}
 
void
PreRestoreCommand(void)
{
    /*
     * Set in_restore_command to tell the signal handler that we should exit
     * right away on SIGTERM. We know that we're at a safe point to do that.
     * Check if we had already received the signal, so that we don't miss a
     * shutdown request received just before this.
     */
    in_restore_command = true;
    if (shutdown_requested)
        proc_exit(1);
}
 
void
PostRestoreCommand(void)
{
    in_restore_command = false;
}
 
bool
IsPromoteSignaled(void)
{
    return promote_signaled;
}
 
void
ResetPromoteSignaled(void)
{
    promote_signaled = false;
}
 
/*
 * Set a flag indicating that it's time to log a progress report.
 */
void
startup_progress_timeout_handler(void)
{
    startup_progress_timer_expired = true;
}
 
void
disable_startup_progress_timeout(void)
{
    /* Feature is disabled. */
    if (log_startup_progress_interval == 0)
        return;
 
    disable_timeout(STARTUP_PROGRESS_TIMEOUT, false);
    startup_progress_timer_expired = false;
}
 
/*
 * Set the start timestamp of the current operation and enable the timeout.
 */
void
enable_startup_progress_timeout(void)
{
    TimestampTz fin_time;
 
    /* Feature is disabled. */
    if (log_startup_progress_interval == 0)
        return;
 
    startup_progress_phase_start_time = GetCurrentTimestamp();
    fin_time = TimestampTzPlusMilliseconds(startup_progress_phase_start_time,
                                           log_startup_progress_interval);
    enable_timeout_every(STARTUP_PROGRESS_TIMEOUT, fin_time,
                         log_startup_progress_interval);
}
 
/*
 * A thin wrapper to first disable and then enable the startup progress
 * timeout.
 */
void
begin_startup_progress_phase(void)
{
    /* Feature is disabled. */
    if (log_startup_progress_interval == 0)
        return;
 
    disable_startup_progress_timeout();
    enable_startup_progress_timeout();
}
 
/*
 * Report whether startup progress timeout has occurred. Reset the timer flag
 * if it did, set the elapsed time to the out parameters and return true,
 * otherwise return false.
 */
bool
has_startup_progress_timeout_expired(long *secs, int *usecs)
{
    long        seconds;
    int         useconds;
    TimestampTz now;
 
    /* No timeout has occurred. */
    if (!startup_progress_timer_expired)
        return false;
 
    /* Calculate the elapsed time. */
    now = GetCurrentTimestamp();
    TimestampDifference(startup_progress_phase_start_time, now, &seconds, &useconds);
 
    *secs = seconds;
    *usecs = useconds;
    startup_progress_timer_expired = false;
 
    return true;
}