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
总结
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