对Postmaster 对 SIGQUIT 信号处理的理解

[作者：技术者高健@博客园  mail: [email protected] ]

Postmaster 作为父进程，要对很多子进程进行监控，当遇到各种信号的时候，也要适当地进行传达。

/*                                

 * pmdie -- signal handler for processing various postmaster signals.                                

 */                                

static void                                

pmdie(SIGNAL_ARGS)                                

{                                

    int            save_errno = errno;                

                                

    PG_SETMASK(&BlockSig);                            

                                

    ereport(DEBUG2,                            

            (errmsg_internal("postmaster received signal %d",                    

                             postgres_signal_arg)));    

                                

    switch (postgres_signal_arg)                            

    {                            

        ……                        

        case SIGQUIT:                        

                                

            /*                    

             * Immediate Shutdown:                    

             *                    

             * abort all children with SIGQUIT and exit without attempt to                    

             * properly shut down data base system.                    

             */                    

            ereport(LOG,                    

                    (errmsg("received immediate shutdown request")));            

            SignalChildren(SIGQUIT);                    

            if (StartupPID != 0)                    

                signal_child(StartupPID, SIGQUIT);                

            if (BgWriterPID != 0)                    

                signal_child(BgWriterPID, SIGQUIT);                

            if (CheckpointerPID != 0)                    

                signal_child(CheckpointerPID, SIGQUIT);                

            if (WalWriterPID != 0)                    

                signal_child(WalWriterPID, SIGQUIT);                

            if (WalReceiverPID != 0)                    

                signal_child(WalReceiverPID, SIGQUIT);                

            if (AutoVacPID != 0)                    

                signal_child(AutoVacPID, SIGQUIT);                

            if (PgArchPID != 0)                    

                signal_child(PgArchPID, SIGQUIT);                

            if (PgStatPID != 0)                    

                signal_child(PgStatPID, SIGQUIT);                

            ExitPostmaster(0);                    

            break;                    

    }                            

                                

    PG_SETMASK(&UnBlockSig);                            

                                

    errno = save_errno;                            

}                                

实验验证：

启动：

[postgres@localhost bin]$ ./postgres -D /usr/local/pgsql/data

LOG:  database system was shut down at 2012-10-31 15:19:46 CST

LOG:  autovacuum launcher started

LOG:  database system is ready to accept connections

发信号：

[postgres@localhost bin]$ ./pg_ctl -D /usr/local/pgsql/data stop -m immediate

waiting for server to shut down.... done

server stopped

[postgres@localhost bin]$ 

后台出现的信息是：

LOG:  received immediate shutdown request

bg_quickdie happend.

WARNING:  terminating connection because of crash of another server process

DETAIL:  The postmaster has commanded this server process to roll back the current transaction and exit, because another server process exited abnormally and possibly corrupted shared memory.

HINT:  In a moment you should be able to reconnect to the database and repeat your command.

[作者：技术者高健@博客园  mail: [email protected] ]

结束