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PostgreSQL pg

时间:2019-02-26  来源:未知  作者:admin666

一、问题
pg_ctl start启动时报错退出:pg_ctl:server did not start in time。超时时间是多少?从什么时候到哪个阶段算超时?

二、分析:该信息打印位置,从后面代码段do_start函数中可以看出
1、pg_ctl start调用start_postmaster启动PG的主进程后,每隔0.1ms检查一次postmaster.pid文件,是否已写入ready/standby
2、总共会检查600次,即从启动主进程后,最多等待60s,如果没有写入ready/standby则打印上述日志并退出
3、默认等待时间是60s,如果pg_ctl start -t指定等待时间,则等待时间为该指定时间

三、什么时候postmaster.pid文件写入ready/standby
1、如果是主机不管有没有设置hot standby
    1)当startup进程恢复完成退出时,调用proc_exit函数向主进程发送SIGCHLD信号并退出
    2)主进程接收到信号后,signal处理函数reaper调用AddToDataDirLockFile向postmaster.pid文件写入ready
2、如果是备机即data目录下有recovery.cnf文件,且设置了hot standby,在实际恢复前没有到达一致性位置
    1)startup进程向主进程发送PMSIGNAL_RECOVERY_STARTED信号,主进程调用信号处理函数sigusr1_handler,将pmState=PM_RECOVERY
    2)每次读取下一个xlog前都会调用CheckRecoveryConsistency函数进行一致性检查:
        2.1 进入一致性状态,starup进程向主进程发送PMSIGNAL_BEGIN_HOT_STANDBY信号,主进程接收到信号后调用sigusr1_handler- AddToDataDirLockFile向postmaster.pid文件写入ready
3、如果是备机即data目录下有recovery.cnf文件,且设置了hot standby,在实际恢复前没有到达一致性位置
    1)startup进程向主进程发送PMSIGNAL_RECOVERY_STARTED信号,主进程调用信号处理函数sigusr1_handler,将pmState=PM_RECOVERY
    2)每次读取下一个xlog前都会调用CheckRecoveryConsistency函数进行一致性检查。如果没有进入一致性状态
    3)本地日志恢复完成,切换日志源时同样调用CheckRecoveryConsistency函数进行一致性检查
        3.1 进入一致性状态,starup进程向主进程发送PMSIGNAL_BEGIN_HOT_STANDBY信号,主进程接收到信号后调用sigusr1_handler- AddToDataDirLockFile向postmaster.pid文件写入ready
4、如果是备机即data目录下有recovery.cnf文件,且设置了hot standby,在实际恢复前到达一致性位置
    1)startup进程向主进程发送PMSIGNAL_RECOVERY_STARTED信号,主进程调用信号处理函数sigusr1_handler,将pmState=PM_RECOVERY
    2)CheckRecoveryConsistency函数进行一致性检查,向主进程发送PMSIGNAL_BEGIN_HOT_STANDBY信号,主进程接收到信号后调用sigusr1_handler- AddToDataDirLockFile向postmaster.pid文件写入ready
5、如果是备机即data目录下有recovery.cnf文件,没有设置hot standby
    1)startup进程向主进程发送PMSIGNAL_RECOVERY_STARTED信号
    2)主进程接收到信号后,向postmaster.将pmState=PM_RECOVERY

四、代码分析
1、pg_ctl start流程

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;

2、server主进程及信号处理函数

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;
    }
    ...

3、Startup进程

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

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