Re: Parallel query vs smart shutdown and Postmaster death

On Tue, Feb 26, 2019 at 5:44 PM Thomas Munro <thomas(dot)munro(at)gmail(dot)com> wrote:
> Then perhaps we could do some more involved surgery on master that
> achieves smart shutdown's stated goal here, and lets parallel queries
> actually run? Better ideas welcome.

I have noticed before that the smart shutdown code does not disclose
to the rest of the system that a shutdown is in progress: no signals
are sent, and no shared memory state is updated. That makes it a bit
challenging for any other part of the system to respond to the smart
shutdown in a way that is, well, smart. But I guess that's not really
the problem in this case.

It seems to me that we could fix pmdie() to skip parallel workers; I
think that the postmaster could notice that they are lagged as
BGWORKER_CLASS_PARALLEL. But we'd also have to fix things so that new
parallel workers could be launched during a smart shutdown, which
looks not quite so simple.

--
Robert Haas
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