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) 1996-2013, PostgreSQL Global Development Group
 *
 *
 * IDENTIFICATION
 *    src/backend/postmaster/startup.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include <signal.h>
#include <unistd.h>

#include "access/xlog.h"
#include "libpq/pqsignal.h"
#include "miscadmin.h"
#include "postmaster/startup.h"
#include "storage/ipc.h"
#include "storage/latch.h"
#include "storage/pmsignal.h"
#include "storage/standby.h"
#include "utils/guc.h"
#include "utils/timeout.h"


/*
 * 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_triggered = 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;

/* Signal handlers */
static void startupproc_quickdie(SIGNAL_ARGS);
static void StartupProcSigUsr1Handler(SIGNAL_ARGS);
static void StartupProcTriggerHandler(SIGNAL_ARGS);
static void StartupProcSigHupHandler(SIGNAL_ARGS);


/* --------------------------------
 *      signal handler routines
 * --------------------------------
 */

/*
 * startupproc_quickdie() occurs when signalled SIGQUIT by the postmaster.
 *
 * Some backend has bought the farm,
 * so we need to stop what we're doing and exit.
 */
static void
startupproc_quickdie(SIGNAL_ARGS)
{
    PG_SETMASK(&BlockSig);

    /*
     * We DO NOT want to run proc_exit() callbacks -- we're here because
     * shared memory may be corrupted, so we don't want to try to clean up our
     * transaction.  Just nail the windows shut and get out of town.  Now that
     * there's an atexit callback to prevent third-party code from breaking
     * things by calling exit() directly, we have to reset the callbacks
     * explicitly to make this work as intended.
     */
    on_exit_reset();

    /*
     * Note we do exit(2) not exit(0).  This is to force the postmaster into a
     * system reset cycle if some idiot DBA sends a manual SIGQUIT to a random
     * backend.  This is necessary precisely because we don't clean up our
     * shared memory state.  (The "dead man switch" mechanism in pmsignal.c
     * should ensure the postmaster sees this as a crash, too, but no harm in
     * being doubly sure.)
     */
    exit(2);
}


/* SIGUSR1: let latch facility handle the signal */
static void
StartupProcSigUsr1Handler(SIGNAL_ARGS)
{
    int         save_errno = errno;

    latch_sigusr1_handler();

    errno = save_errno;
}

/* SIGUSR2: set flag to finish recovery */
static void
StartupProcTriggerHandler(SIGNAL_ARGS)
{
    int         save_errno = errno;

    promote_triggered = 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;
}

/* Handle SIGHUP and SIGTERM signals of startup process */
void
HandleStartupProcInterrupts(void)
{
    /*
     * Check if we were requested to re-read config file.
     */
    if (got_SIGHUP)
    {
        got_SIGHUP = false;
        ProcessConfigFile(PGC_SIGHUP);
    }

    /*
     * 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.
     */
    if (IsUnderPostmaster && !PostmasterIsAlive())
        exit(1);
}


/* ----------------------------------
 *  Startup Process main entry point
 * ----------------------------------
 */
void
StartupProcessMain(void)
{
    /*
     * If possible, make this process a group leader, so that the postmaster
     * can signal any child processes too.
     */
#ifdef HAVE_SETSID
    if (setsid() < 0)
        elog(FATAL, "setsid() failed: %m");
#endif

    /*
     * 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 */
    pqsignal(SIGQUIT, startupproc_quickdie);    /* hard crash time */
    InitializeTimeouts();       /* establishes SIGALRM handler */
    pqsignal(SIGPIPE, SIG_IGN);
    pqsignal(SIGUSR1, StartupProcSigUsr1Handler);
    pqsignal(SIGUSR2, StartupProcTriggerHandler);

    /*
     * Reset some signals that are accepted by postmaster but not here
     */
    pqsignal(SIGCHLD, SIG_DFL);
    pqsignal(SIGTTIN, SIG_DFL);
    pqsignal(SIGTTOU, SIG_DFL);
    pqsignal(SIGCONT, SIG_DFL);
    pqsignal(SIGWINCH, SIG_DFL);

    /*
     * Register timeouts needed for standby mode
     */
    RegisterTimeout(STANDBY_DEADLOCK_TIMEOUT, StandbyDeadLockHandler);
    RegisterTimeout(STANDBY_TIMEOUT, StandbyTimeoutHandler);

    /*
     * Unblock signals (they were blocked when the postmaster forked us)
     */
    PG_SETMASK(&UnBlockSig);

    /*
     * 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
IsPromoteTriggered(void)
{
    return promote_triggered;
}

void
ResetPromoteTriggered(void)
{
    promote_triggered = false;
}