Re: [PATCH] Verify Checksums during Basebackups

From: Michael Banck <michael(dot)banck(at)credativ(dot)de>
To: Stephen Frost <sfrost(at)snowman(dot)net>
Cc: Magnus Hagander <magnus(at)hagander(dot)net>, PostgreSQL Developers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: [PATCH] Verify Checksums during Basebackups
Date: 2018-03-05 11:47:17
Message-ID: 1520250437.22202.13.camel@credativ.de
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Hi,

Am Montag, den 05.03.2018, 06:36 -0500 schrieb Stephen Frost:
> Michael,
>
> * Michael Banck (michael(dot)banck(at)credativ(dot)de) wrote:
> > On Sun, Mar 04, 2018 at 06:19:00PM +0100, Magnus Hagander wrote:
> > > So sure, if we go with WARNING + exit with an errorcode, that is perhaps
> > > the best combination of the two.
> >
> > I had a look at how to go about this, but it appears to be a bit
> > complicated; the first problem is that sendFile() and sendDir() don't
> > have status return codes that could be set on checksum verifcation
> > failure. So I added a global variable and threw an ereport(ERROR) at the
> > end of perform_base_backup(), but then I realized that `pg_basebackup'
> > the client program purges the datadir it created if it gets an error:
> >
> > > pg_basebackup: final receive failed: ERROR: Checksum mismatch during
> > > basebackup
> > >
> > > pg_basebackup: removing data directory "data2"
>
> Oh, ugh.

I came up with the attached patch, which sets a checksum_failure
variable in both basebackup.c and pg_basebackup.c, and emits an ereport
with (for now) ERRCODE_DATA_CORRUPTED at the end of
perform_base_backup(), which gets caught in pg_basebackup and then used
to not cleanup the datadir, but exit with a non-zero exit code.

Does that seem feasible?

Michael

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Michael Banck
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Attachment Content-Type Size
checksum_basebackup_error_checking.patch text/x-patch 3.5 KB

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