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Re: Revised patch for fixing archiver shutdown behavior

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
Cc: pgsql-patches(at)postgreSQL(dot)org, Simon Riggs <simon(at)2ndquadrant(dot)com>
Subject: Re: Revised patch for fixing archiver shutdown behavior
Date: 2008-01-10 15:49:28
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-patches
Alvaro Herrera <alvherre(at)commandprompt(dot)com> writes:
> Tom Lane wrote:
>> Maybe we should go back to the plan of having the postmaster
>> wait for the archiver to exit.

> Yeah, that seems the safest to me -- the problem is that it complicates
> the shutdown sequence a fair bit, because postmaster must act
> differently depending on whether archiving is enabled or not: wait for
> bgwriter exit if disabled, or for archiver exit otherwise.

Given the recent changes to make the postmaster act as a state machine,
I don't think this is really a big deal --- it's just one more state.
The bigger part is that the archiver can't wait for postmaster exit.
We'll need a proper shutdown signal for the archiver, but since it's
not using SIGUSR2 that can be commandeered easily.  So it'd be like

	SIGUSR1 -> do an archive cycle
	SIGUSR2 -> do an archive cycle and exit
	no postmaster -> just exit

The rationale for the last is that it's a crash situation, and
furthermore there's a risk of someone starting a new postmaster
and a conflicting archiver.  So we should put back the behavior
my last patch removed of aborting archiving immediately on
postmaster death.

I'll respin my patch this way...

			regards, tom lane

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Subject: Re: Revised patch for fixing archiver shutdown behavior
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