From: Tom Lane <tgl@sss.pgh.pa.us>
To: Achilleas Mantzios <achill@matrix.gatewaynet.com>
Cc: pgsql-admin@lists.postgresql.org
Subject: Re: PostgreSQL 10.5 : Strange pg_wal fill-up, solved with the shutdown checkpoint
Date: Tue, 06 Nov 2018 09:58:23 -0500
Message-ID: <23169.1541516303@sss.pgh.pa.us> (raw)
In-Reply-To: <6031b670-52d1-b823-6b41-35d2fa1873c6@matrix.gatewaynet.com>
References: <0d25bb8c-9cc7-10bc-71ba-6a8a8c33ec49@matrix.gatewaynet.com>
<46D70340-2172-406A-A346-B2D4C6E947E4@crazybean.net>
<6031b670-52d1-b823-6b41-35d2fa1873c6@matrix.gatewaynet.com>
Achilleas Mantzios <achill@matrix.gatewaynet.com> writes:
> Remember : postgresql checkpointer decided to remove 5000+ files before shutdown. If any conditions were keeping those files afloat should also hold at this point, right.
> The question is why didn't Postgresql removed them earlier.
WAL files get removed/recycled after completion of a checkpoint. So
apparently, checkpoints were not finishing during normal operation,
but the shutdown checkpoint managed to terminate normally. That
eliminates a lot of the usual theories about why checkpoints might
not be succeeding (like a dirty buffer that always fails to be
written, say as a result of broken permissions on its file).
The only theory that comes to mind is that the checkpointer process
was stuck somehow, but just "soft" stuck, in a way that allowed the
postmaster's time-to-shut-down-please signal to unstick it. No,
I have no idea how that could happen exactly. If it happens again,
it'd be really interesting to attach to the checkpointer with a
debugger and collect a stack trace.
regards, tom lane
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To: pgsql-admin@postgresql.org
Cc: tgl@sss.pgh.pa.us, achill@matrix.gatewaynet.com, pgsql-admin@lists.postgresql.org
Subject: Re: PostgreSQL 10.5 : Strange pg_wal fill-up, solved with the shutdown checkpoint
In-Reply-To: <23169.1541516303@sss.pgh.pa.us>
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