Re: 'Shutdown <= SmartShutdown' check while launching processes in postmaster.

shveta malik <shveta(dot)malik(at)gmail(dot)com> writes:
> I would like to know that why we have 'Shutdown <= SmartShutdown'
> check before launching few processes (WalReceiver, WalSummarizer,
> AutoVacuum worker) while rest of the processes (BGWriter, WalWriter,
> Checkpointer, Archiver etc) do not have any such check. If I have to
> launch a new process, what shall be the criteria to decide if I need
> this check?

Children that are stopped by the "if (pmState == PM_STOP_BACKENDS)"
stanza in PostmasterStateMachine should not be allowed to start
again later if we are trying to shut down. (But "smart" shutdown
doesn't enforce that, since it's a very weak state that only
prohibits new client sessions.) The processes that are allowed
to continue beyond that point are ones that are needed to perform
the shutdown checkpoint, or useful to make it finish faster.

regards, tom lane