From: | Justin Pryzby <pryzby(at)telsasoft(dot)com> |
---|---|
To: | Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com> |
Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Jakub Glapa <jakub(dot)glapa(at)gmail(dot)com>, Fabio Isabettini <fisabettini(at)voipfuture(dot)com>, Arne Roland <A(dot)Roland(at)index(dot)de>, Sand Stone <sand(dot)m(dot)stone(at)gmail(dot)com>, Rick Otten <rottenwindfish(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
Subject: | Re: dsa_allocate() faliure |
Date: | 2019-02-11 00:02:15 |
Message-ID: | 20190211000215.GU31721@telsasoft.com |
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Lists: | pgsql-hackers pgsql-performance |
On Mon, Feb 11, 2019 at 09:45:07AM +1100, Thomas Munro wrote:
> Ouch. Yeah, that'd do it and matches the evidence. With this change,
> I couldn't reproduce the problem after 90 minutes with a test case
> that otherwise hits it within a couple of minutes.
...
> Note that this patch addresses the error "dsa_allocate could not find
> %zu free pages". (The error "dsa_area could not attach to segment" is
> something else and apparently rarer.)
"could not attach" is the error reported early this morning while
stress-testing this patch with queued_alters queries in loops, so that's
consistent with your understanding. And I guess it preceded getting stuck on
lock; although I don't how long between the first happened and the second, I'm
guess not long and perhaps immedidately; since the rest of the processes were
all stuck as in bug#15585 rather than ERRORing once every few minutes.
I mentioned that "could not attach to segment" occurs in leader either/or
parallel worker. And most of the time causes an ERROR only, and doesn't wedge
all future parallel workers. Maybe bug#15585 "wedged" state maybe only occurs
after some pattern of leader+worker failures (?) I've just triggered bug#15585
again, but if there's a pattern, I don't see it.
Please let me know whether you're able to reproduce the "not attach" bug using
simultaneous loops around the queued_alters query; it's easy here.
Justin
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