PostgreSQL神秘进程的观察

在PostgreSQL运行的时候，通过对其代码进行跟踪，发现不断有进程被生成，访问InitFileAccess，过了大约20秒左右，就死掉了。

这个过程反复地进行着，进程号不断增加。

我对其进一步进行了跟踪，发现似乎是这些进程是为了 autovacuum 而被创建出来，然后自己消亡的。

在PostgreSQL9.2源代码中加入：

InitFileAccess(void)
{

    fprintf(stderr,"In %s ...by Process %d\n", __FUNCTION__,getpid());
    fprintf(stderr,"----------------------------------------------------\n\n");

    ...
}

void
BaseInit(void)
{

    fprintf(stderr,"In %s ...by Process %d\n", __FUNCTION__,getpid());

    /*
     * Attach to shared memory and semaphores, and initialize our
     * input/output/debugging file descriptors.
     */
    InitCommunication();
    DebugFileOpen();

    /* Do local initialization of file, storage and buffer managers */
    InitFileAccess();
    smgrinit();
    InitBufferPoolAccess();
}

NON_EXEC_STATIC void
AutoVacLauncherMain(int argc, char *argv[])
{
    ...
    fprintf(stderr,"In %s ...by Process %d\n", __FUNCTION__,getpid());

    /* Early initialization */
    BaseInit();
    ...
    proc_exit(0);                /* done */
}

NON_EXEC_STATIC void
AutoVacWorkerMain(int argc, char *argv[])
{
    ...
    fprintf(stderr,"In %s ...by Process %d\n", __FUNCTION__,getpid());

    /* Early initialization */
    BaseInit();
    ...

    /* All done, go away */
    proc_exit(0);
}

执行结果如下：

[postgres@lex bin]$ ./pg_ctl -D ../data start
server starting
[postgres@lex bin]$ In BaseInit ...by Process 4804
In InitFileAccess ...by Process 4804
----------------------------------------------------

LOG:  database system was shut down at 2013-05-24 14:29:46 CST
In BaseInit ...by Process 4805
In InitFileAccess ...by Process 4805
----------------------------------------------------

In BaseInit ...by Process 4806
In InitFileAccess ...by Process 4806
----------------------------------------------------

In BaseInit ...by Process 4807
In InitFileAccess ...by Process 4807
----------------------------------------------------

LOG:  autovacuum launcher started
In AutoVacLauncherMain ...by Process 4808
In BaseInit ...by Process 4808
In InitFileAccess ...by Process 4808
----------------------------------------------------

LOG:  database system is ready to accept connections
In AutoVacWorkerMain ...by Process 4816
In BaseInit ...by Process 4816
In InitFileAccess ...by Process 4816
----------------------------------------------------

In AutoVacWorkerMain ...by Process 4823
In BaseInit ...by Process 4823
In InitFileAccess ...by Process 4823
----------------------------------------------------

In AutoVacWorkerMain ...by Process 4830
In BaseInit ...by Process 4830
In InitFileAccess ...by Process 4830
----------------------------------------------------