Re: Archiver behavior at shutdown

Alvaro Herrera <alvherre@commandprompt.com> writes:
> What does postmaster do then?  Sleep until archiver is done, or exit
> immediately and hope that the archiver goes away as soon as it finishes?

I think it can just exit immediately, particularly if we invent the
variant signal for "archive what you can and then quit".

> If the former, then we open the possibility that postmaster lives far
> too long before system shutdown decides to SIGKILL it.  If the latter,
> then a subsequent postmaster start could initiate a second archiver
> process which would cause issues with whatever the first archiver is
> doing.

That's a problem that the archiver itself should fix (perhaps it needs
its own lockfile).  Consider kill -9 on the postmaster followed by
starting a fresh postmaster --- you have the same problem, and there's
nothing much the postmaster can do about it.

> I think your proposal to handle SIGTERM could also be used whenever
> postmaster has been asked for shutdown (except smart shutdown,
> perhaps?):

>> I suggest that the response to SIGTERM ought to be to finish
>> out the current copy operation (if possible) but then quit without
>> initiating any new ones.

No, because during normal shutdown we'd like the archiver to copy away
*all* available segments, not just one.
        regards, tom lane