PostgreSQL pg_ctl start启动超时实例分析

do_start->

  pm_pid = start_postmaster();

  if (do_wait){

   print_msg(_( "waiting for server to start..." ));

   switch (wait_for_postmaster(pm_pid, false )){

    case POSTMASTER_READY:

     print_msg(_( " done\n" ));

     print_msg(_( "server started\n" ));

     break ;

    case POSTMASTER_STILL_STARTING:

     print_msg(_( " stopped waiting\n" ));

     write_stderr(_( "%s: server did not start in time\n" ), progname);

     exit (1);

     break ;

    case POSTMASTER_FAILED:

     print_msg(_( " stopped waiting\n" ));

     write_stderr(_( "%s: could not start server\n" "Examine the log output.\n" ), progname);

     exit (1);

     break ;

   }

  } else

   print_msg(_( "server starting\n" ));

wait_for_postmaster->

  for (i = 0; i < wait_seconds * WAITS_PER_SEC; i++){

   if ((optlines = readfile(pid_file, &numlines)) != NULL && numlines >= LOCK_FILE_LINE_PM_STATUS){

    pmpid = atol (optlines[LOCK_FILE_LINE_PID - 1]);

    pmstart = atol (optlines[LOCK_FILE_LINE_START_TIME - 1]);

    if (pmstart >= start_time - 2 && pmpid == pm_pid){

     char   *pmstatus = optlines[LOCK_FILE_LINE_PM_STATUS - 1];

     if ( strcmp (pmstatus, PM_STATUS_READY) == 0 || strcmp (pmstatus, PM_STATUS_STANDBY) == 0){

      /* postmaster is done starting up */

      free_readfile(optlines);

      return POSTMASTER_READY;

     }

    }

   }

   free_readfile(optlines);

   if (waitpid((pid_t) pm_pid, &exitstatus, WNOHANG) == (pid_t) pm_pid)

    return POSTMASTER_FAILED;

   pg_usleep(USEC_PER_SEC / WAITS_PER_SEC);

  }

  /* out of patience; report that postmaster is still starting up */

  return POSTMASTER_STILL_STARTING;

PostmasterMain->

  pqsignal_no_restart(SIGUSR1, sigusr1_handler); /* message from child process */

  pqsignal_no_restart(SIGCHLD, reaper); /* handle child termination */

  ...

  StartupXLOG();

  ...

  proc_exit(0); //exit函数向主进程发送SIGCHLD信号

reaper-> //进程终止或者停止的信号

  AddToDataDirLockFile(LOCK_FILE_LINE_PM_STATUS, PM_STATUS_READY);

postmaster进程接收信号：

sigusr1_handler->

  if (CheckPostmasterSignal(PMSIGNAL_RECOVERY_STARTED) &&

   pmState == PM_STARTUP && Shutdown == NoShutdown){

   CheckpointerPID = StartCheckpointer();

   BgWriterPID = StartBackgroundWriter();

   if (XLogArchivingAlways())

    PgArchPID = pgarch_start();

   //hot_standby在postgresql.conf文件中配置TRUE

   //表示在恢复的时候允许连接

   if (!EnableHotStandby){

    //将standby写入postmaster.pid文件，表示up但不允许连接

    AddToDataDirLockFile(LOCK_FILE_LINE_PM_STATUS, PM_STATUS_STANDBY);

   }

   pmState = PM_RECOVERY;

  }

  if (CheckPostmasterSignal(PMSIGNAL_BEGIN_HOT_STANDBY) &&

   pmState == PM_RECOVERY && Shutdown == NoShutdown){

   PgStatPID = pgstat_start();

   //将ready写入postmaster.pid文件，允许连接

   AddToDataDirLockFile(LOCK_FILE_LINE_PM_STATUS, PM_STATUS_READY);

   pmState = PM_HOT_STANDBY;

  }

  ...

StartupXLOG->

  ReadCheckpointRecord

  if (ArchiveRecoveryRequested && IsUnderPostmaster){ //有recovery.conf文件则ArchiveRecoveryRequested为TRUE

   //有recovery.conf文件则ArchiveRecoveryRequested为TRUE

   PublishStartupProcessInformation();

   SetForwardFsyncRequests();

   //向master进程发送PMSIGNAL_RECOVERY_STARTED信号

   SendPostmasterSignal(PMSIGNAL_RECOVERY_STARTED);

   bgwriterLaunched = true ;

  }

  CheckRecoveryConsistency();-->...

  |-- if (standbyState == STANDBY_SNAPSHOT_READY && !LocalHotStandbyActive &&

  |  reachedConsistency && IsUnderPostmaster){

  |  SpinLockAcquire(&XLogCtl->info_lck);

  |  XLogCtl->SharedHotStandbyActive = true ;

  |  SpinLockRelease(&XLogCtl->info_lck);

  |  LocalHotStandbyActive = true ;

  |  SendPostmasterSignal(PMSIGNAL_BEGIN_HOT_STANDBY);

  |-- }

  ...

  回放一个record后，每次读取下一个record前都会调用CheckRecoveryConsistency