From: Michael Banck <michael.banck@credativ.de>
To: Michael Paquier <michael@paquier.xyz>
Cc: Magnus Hagander <magnus@hagander.net>
Cc: Fabien COELHO <coelho@cri.ensmp.fr>
Cc: Sergei Kornilov <sk@zsrv.org>
Cc: PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>
Subject: Re: Offline enabling/disabling of data checksums
Date: Fri, 15 Mar 2019 09:04:51 +0100
Message-ID: <1552637091.9697.18.camel@credativ.de> (raw)
In-Reply-To: <20190315025027.GN3493@paquier.xyz>
References: <20190313021621.GP13812@paquier.xyz>
<alpine.DEB.2.21.1903130805330.4059@lancre>
<20190313093150.GE2988@paquier.xyz>
<1552473675.4947.62.camel@credativ.de>
<CABUevExWFGMZktS2UEYfKbgsEKLVnrQxv5M8GMYFgiBmQy+cNA@mail.gmail.com>
<1552475364.4947.64.camel@credativ.de>
<20190313115633.GA1878@paquier.xyz>
<20190314043936.GH3493@paquier.xyz>
<CABUevExjCOKDRX=B6fBkoYs7Q2jYJLZS4Bxh1pi0b2_BV-7DEA@mail.gmail.com>
<1552577180.9697.4.camel@credativ.de>
<20190315025027.GN3493@paquier.xyz>
Hi,
Am Freitag, den 15.03.2019, 11:50 +0900 schrieb Michael Paquier:
> On Thu, Mar 14, 2019 at 04:26:20PM +0100, Michael Banck wrote:
> > Am Donnerstag, den 14.03.2019, 15:26 +0100 schrieb Magnus Hagander:
> > > One big-hammer method could be similar to what pg_upgrade does --
> > > temporarily rename away the controlfile so postgresql can't start, and
> > > when done, put it back.
> >
> > That sounds like a good solution to me. I've made PoC patch for that,
> > see attached.
>
> Indeed. I did not know this trick from pg_upgrade. We could just use
> the same.
>
> > The only question is whether pg_checksums should try to move pg_control
> > back (i) on failure (ii) when interrupted?
>
> Yes, we should have a callback on SIGINT and SIGTERM here which just
> moves back in place the control file if the temporary one exists. I
> have been able to grab some time to incorporate the feedback gathered
> on this thread, and please find attached a new version of the patch to
> add --enable/--disable.
Thanks!
One thing stood out to me while quickly looking over it:
+ /*
+ * Flush the control file and its parent path to make the change
+ * durable.
+ */
+ if (fsync_fname(controlfile_path, false, progname) != 0 ||
+ fsync_parent_path(controlfile_path, progname) != 0)
+ {
+ /* errors are already logged on failure */
+ exit(1);
+ }
ISTM this would not run fsync_parent_path() unless the first fsync fails
which is not the intended use. I guess we need two ifs here?
Michael
--
Michael Banck
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To: pgsql-hackers@postgresql.org
Cc: michael.banck@credativ.de, michael@paquier.xyz, magnus@hagander.net, coelho@cri.ensmp.fr, sk@zsrv.org, pgsql-hackers@lists.postgresql.org
Subject: Re: Offline enabling/disabling of data checksums
In-Reply-To: <1552637091.9697.18.camel@credativ.de>
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