记忆方法：3 + 5 + 8 + 5

postgres  118495      1    /opt/pgsql10.12/bin/postgres
postgres  18674  118495  postgres: logger process  
postgres  18686  118495  postgres: checkpointerprocess 
postgres  18687  118495  postgres: writer process  
postgres  18688  118495  postgres: wal writerprocess 
postgres  18689  118495  postgres: autovacuum launcherprocess 
postgres  18690  118495  postgres: stats collectorprocess 
postgres  18691  118495  postgres: bgworker: logicalreplication launcher 
postgres  46841  118495  postgres: postgres postgres[local] idle


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src/bin/pg_ctl/pg_ctl.c
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src/backend/postmaster/postmaster.c
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ListenAddresses
/* The TCP listen address(es) */
char   *ListenAddresses;
       if (ListenAddresses) (IP地址才能判断为真)
              char  *rawstring;
              List    *elemlist;
              ListCell           *l;
              int      success = 0;


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bacend process
/*
 * BackendStartup -- start backend process
 *
 * returns: STATUS_ERROR if the fork failed,STATUS_OK otherwise.
 *
 * Note: if you change this code, also considerStartAutovacuumWorker.
 */
static int
BackendStartup(Port*port)
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src/backend/tcop/postgres.c
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为用户交互连接调用InteractiveBackend（）
static int
InteractiveBackend(StringInfo inBuf)
{
       intc; /* character read from getc() */
       /*
        * display a prompt and obtain input from theuser
        */
       printf("backend>");
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tcp_keepalives_idle
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tcp_keepalives_interval
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tcp_keepalives_count
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tcp_user_timeout
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src/backend/postmaster/checkpointer.c




src/include/catalog/pg_control.h
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 */
typedef structCheckPoint
{
        XLogRecPtr       redo;/* 创建存盘时下一个可用的RecPtr(即重做点)*/
        TimeLineID        ThisTimeLineID;        /*当前时间线 ID TLI */
        TimeLineID        PrevTimeLineID;        /*当前一个时间线*/
        boolfullPageWrites;   /* 当前整页写入的状态*/
        uint32       nextXidEpoch;   /* 下一个事物ID的高位*/
        TransactionId nextXid;        /*下一个空闲事物ID */
        Oid   nextOid;    /* 下一个空闲Oid*/
        MultiXactId nextMulti;        /*下一个空闲 MultiXactId */
        MultiXactOffset nextMultiOffset;/* 下一个空闲 MultiXact 偏移量 */
        TransactionId oldestXid;     /* 集簇范围最小的 datfrozenxid */
        Oid   oldestXidDB;     /* 带有最小datfrozenxid的数据库 */
        MultiXactId oldestMulti;     /* 集簇范围内最小的datfrozenxid */
        Oid   oldestMultiDB;   /* 带有最小datminmxid的数据库 */
        pg_time_t  time;/* 存盘时间栈*/
        TransactionId oldestCommitTsXid;      /* oldest Xid with valid commit *timestamp */
        TransactionId newestCommitTsXid;     /* newest Xid with valid commit * timestamp*/
        /*
         *最老的XID仍在运行。这只需要从在线检查点初始化热备用模式，所以我们只需要为在线检查点计算这一点，并且仅当wal_级别为副本时。否则它将设置为InvalidTransactionId。
         */
        TransactionId oldestActiveXid;
} CheckPoint;
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src/backend/postmaster/bgwriter.c
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 */
void
BackgroundWriterMain(void)
{
       sigjmp_buf     local_sigjmp_buf;
       MemoryContextbgwriter_context;
       bool       prev_hibernate;
       WritebackContextwb_context;
       /*
        * Properly accept or ignore signals thepostmaster might send us.
        *
        * bgwriter doesn't participate in ProcSignalsignalling, but a SIGUSR1
        * handler is still needed for latch wakeups.
        */
…………………
}
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bgwriter_delay = 200ms                 # 10-10000ms between rounds
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bgwriter_lru_maxpages = 100            # 0-1000 max buffers written/round
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bgwriter_lru_multiplier = 2.0          # 0-10.0 multiplier on buffersscanned/round
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bgwriter_flush_after = 512kB           # measured in pages, 0 disables
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WalWriterMain();src/backend/postmaster/walwriter.c
/*
WalWriter process，主入口函数是WalWriterMain(void)
 */
Void WalWriterMain(void)
{
       sigjmp_buf     local_sigjmp_buf;
       MemoryContextwalwriter_context;
       int                 left_till_hibernate;
       bool       hibernating;
       /*
        * Properly accept or ignore signals thepostmaster might send us
        *
        * We have no particular use for SIGINT at themoment, but seems
        * reasonable to treat like SIGTERM.
        */
       pqsignal(SIGHUP,WalSigHupHandler); /* set flag to read config file */
       pqsignal(SIGINT,WalShutdownHandler);   /* request shutdown*/
       pqsignal(SIGTERM,WalShutdownHandler);       /* requestshutdown */
       pqsignal(SIGQUIT,wal_quickdie);/* hard crash time */
       pqsignal(SIGALRM,SIG_IGN);
       pqsignal(SIGPIPE,SIG_IGN);
       pqsignal(SIGUSR1,walwriter_sigusr1_handler);
       pqsignal(SIGUSR2,SIG_IGN); /* not used */
… …


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src/backend/postmaster/autovacuum.c
* Main loop for the autovacuum launcherprocess.
 *autovacuum进程主循环
 */
NON_EXEC_STATIC void
AutoVacLauncherMain(int argc, char *argv[])
{* 在某个worker仍然在启动时,不能启动新的worker,因此休眠一段时间;
            * 另外一个worker在ready后会第一时间唤醒我们.
            * 只需要等待autovacuum_naptime参数设置的时间(单位秒)(最大为60s).
            * 注意,在这里不能够连接一个特定的数据库不存在任何问题,因为worker在
            *   尝试连接时,通过startingWorker指针销毁自己.
            * 通过postmaster检测到问题(如fork()失败)会报告并且进行不同的处理,
            *   这里唯一的问题是可能导致这里的处理逻辑在AutoVacWorkerMain的早起触发错误,
            * 而且是在worker通过startingWorker指针清除WorkerInfo前.
            */
           waittime = Min(autovacuum_naptime, 60) * 1000;
           if (TimestampDifferenceExceeds(worker->wi_launchtime, current_time,
                                          waittime))
           {}
… …
}
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src/backend/postmaster/pgstat.c
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int
pgstat_start(void)
{
   time_t      curtime;
   pid_t       pgStatPid;
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 if (pgStatSock == PGINVALID_SOCKET)
        return 0;
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   curtime = time(NULL);
   if ((unsigned int) (curtime - last_pgstat_start_time) <
       (unsigned int) PGSTAT_RESTART_INTERVAL)
       return 0;
   last_pgstat_start_time = curtime;
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void
PostgresMain(int argc, char *argv[],
            const char *dbname,
            const char *username)
{
/*
    * Set up signal handlers and masks.
    * 配置信号handlers和masks.
    *
    * Note that postmaster blocked all signals before forking child process,
    * so there is no race condition whereby we might receive a signal before
    * we have set up the handler.
    * 注意在fork子进程前postmaster已阻塞了所有信号,
    *   因此就算接收到信号,但在完成配置handler前不会存在条件争用.
    *
    * Also note: it's best not to use any signals that are SIG_IGNored inthe
    * postmaster.  If such a signalarrives before we are able to change the
    * handler to non-SIG_IGN, it'll get dropped.  Instead, make a dummy
     * handler in the postmaster to reserve thesignal. (Of course, this isn't
    * an issue for signals that are locally generated, such as SIGALRM and
    * SIGPIPE.)
    * 同时注意:最好不要使用在postmaster中标记为SIG_IGNored的信号.
    * 如果在改变处理器为non-SIG_IGN前,接收到这样的信号,会被清除.
    * 相反,可以在postmaster中创建dummy handler来保留这样的信号.
    * (当然,对于本地产生的信号,比如SIGALRM和SIGPIPE,这不会是问题)
    */
   if (am_walsender)//wal sender进程？
       WalSndSignals();//如果是，则调用WalSndSignals
   else//不是wal sender进程
    {
       //设置标记,读取配置文件
       pqsignal(SIGHUP, PostgresSigHupHandler);    /* set flag to read config
                                                    * file */
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//中断信号处理器(中断当前查询)
       pqsignal(SIGINT, StatementCancelHandler);   /* cancel current query */
       //终止当前查询并退出
       pqsignal(SIGTERM, die); /* cancel current query and exit */
       /*
        * In a standalone backend, SIGQUIT can be generated from the keyboard
        * easily, while SIGTERM cannot, so we make both signals do die()
        * rather than quickdie().
        * 在standalone进程,SIGQUIT可很容易的通过键盘生成,而SIGTERM则不好生成,
        *   因此让这两个信号执行die()而不是quickdie().
        */
//bool IsUnderPostmaster = false
       if (IsUnderPostmaster)
           //悲催时刻,执行quickdie()
           pqsignal(SIGQUIT, quickdie);    /*hard crash time */
       else
           //执行die()
           pqsignal(SIGQUIT, die); /* cancel current query and exit */
       //建立SIGALRM处理器
       InitializeTimeouts();   /* establishesSIGALRM handler */
       /*
        * Ignore failure to write to frontend. Note: if frontend closes
        * connection, we will notice it and exit cleanly when control next
        * returns to outer loop.  Thisseems safer than forcing exit in the
        * midst of output during who-knows-what operation...
        * 忽略写入前端的错误.
        * 注意:如果前端关闭了连接,会通知并在空中下一次返回给外层循环时退出.
        * 这看起来会比在who-knows-what操作期间强制退出安全一些.
        */
       pqsignal(SIGPIPE, SIG_IGN);
       pqsignal(SIGUSR1, procsignal_sigusr1_handler);
       pqsignal(SIGUSR2, SIG_IGN);
       pqsignal(SIGFPE, FloatExceptionHandler);
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src/backend/postmaster/pgarch.c
/*
 *pgarch_start
 *
在启动时或现有archiver died从postmaster处调用。尝试启动一个新的归档进程。返回子进程的PID，
如果失败则返回0。注意：如果失败，将从postmaster主循环再次调用我们。
 */
int
pgarch_start(void)
{
       time_t            curtime;
       pid_t              pgArchPid;
       /*
如果从上次归档开始太快，请不要执行任何操作。这是一个安全阀，用于防止在执行时archiver立即dying 的情况下持续重生。
请注意，因为我们将从postmaster主循环重新调用，所以稍后我们将获得另一个机会。*/
       curtime= time(NULL);
      if((unsigned int) (curtime - last_pgarch_start_time) <
              (unsignedint) PGARCH_RESTART_INTERVAL)
              return0;
       last_pgarch_start_time= curtime;
… …
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src/backend/postmaster/syslogger.c
/* syslogger process 主入口 */
NON_EXEC_STATIC void
SysLoggerMain(int argc, char *argv[])
{
#ifndef WIN32
   char       logbuffer[READ_BUF_SIZE];
   int         bytes_in_logbuffer =0;
#endif
   char     *currentLogDir;
   char     *currentLogFilename;
   int         currentLogRotationAge;
   pg_time_t   now;
   now = MyStartTime;
#ifdef EXEC_BACKEND
    syslogger_parseArgs(argc, argv);
#endif                          /* EXEC_BACKEND */
   am_syslogger = true;
   init_ps_display("logger", "", "","");
   /* 如果重新启动，我们的STDRR已经被重定向到我们自己的输入管道中。这当然是无用的，
       更不用说它干扰检测管EOF。把stderr只想到/dev/null 。假设 syslogger 中生成的所有的消息将通过
       elog.c发送到 write_syslogger_file 。*/
   if (redirection_done)
    {
       int         fd = open(DEVNULL,O_WRONLY, 0);
    /* 关闭可能看起来是多余，但实际上并不是：我们要确保管道即使打开失败也会关闭。我们可以在stderr 指向任何地方运行，但我们不能负担额外的管道输入描述符。由于我们只是试图将这些重置为DEVNULL，所以在这里从close/dup2调用中检查失败没有多大意义，如果它们失败，那么可能文件描述符被关闭，并且任何写入都将进入 bitbucket 。*/
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