Date: Thu, 30 Aug 2018 11:57:05 -0700
From: Michael Paquier <michael@paquier.xyz>
To: Alexander Kukushkin <cyberdemn@gmail.com>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>,
	Alvaro Herrera <alvherre@2ndquadrant.com>,
	Dmitry Dolgov <9erthalion6@gmail.com>,
	pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #15346: Replica fails to start after the crash
Message-ID: <20180830185705.GF15446@paquier.xyz>
References: <20180829061723.GA5903@paquier.xyz>
 <CAFh8B=kuFyBsth-1wuPqncnTiCa7reKzCz=RzO1X-Y78U74F5g@mail.gmail.com>
 <20180829121051.GC5903@paquier.xyz>
 <CAFh8B==_6cY1f7rF4oxK+wjpWKaYzs96Q6Tn5=4QRWJiVnjmDg@mail.gmail.com>
 <20180829205436.GE5903@paquier.xyz>
 <CAFh8B=n-NSo2Ktz_DG3W4FAFr2xHYr7FyRNdOF6g7T2o1-CD4w@mail.gmail.com>
 <20180830133911.GA15446@paquier.xyz>
 <CAFh8B==_Acxr_-K0iRfWdVoAn_pfgzpvu+5AsdaWTEkttwhnnw@mail.gmail.com>
 <20180830173435.GB15446@paquier.xyz>
 <CAFh8B==uFj619A8dY1evowLxj_J=9mO29ONw_QHqSLsRQM5ZWw@mail.gmail.com>
MIME-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha512;
	protocol="application/pgp-signature"; boundary="jaoouwwPWoQSJZYp"
Content-Disposition: inline
In-Reply-To: 
 <CAFh8B==uFj619A8dY1evowLxj_J=9mO29ONw_QHqSLsRQM5ZWw@mail.gmail.com>
Precedence: bulk


--jaoouwwPWoQSJZYp
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

On Thu, Aug 30, 2018 at 08:31:36PM +0200, Alexander Kukushkin wrote:
> 2018-08-30 19:34 GMT+02:00 Michael Paquier <michael@paquier.xyz>:
>> I have been struggling for a couple of hours to get a deterministic test
>> case out of my pocket, and I did not get one as you would need to get
>> the bgwriter to flush a page before crash recovery finishes, we could do
>=20
> In my case the active standby server has crashed, it wasn't in the
> crash recovery mode.

That's what I meant, a standby crashed and then restarted, doing crash
recovery before moving on with archive recovery once it was done with
all its local WAL.

> Minimum recovery ending location is AB3/4A1B3118, but at the same time
> I managed to find pages from 0000000500000AB300000053 on disk (at
> least in the index files). That could only mean that bgwriter was
> flushing dirty pages, but pg_control wasn't properly updated and it
> happened not during recovery after hardware crash, but while the
> postgres was running before the hardware crash.

Exactly, that would explain the incorrect reference.

> The only possible way to recover such standby - cut off all possible
> connections and let it replay all WAL files it managed to write to
> disk before the first crash.

Yeah...  I am going to apply the patch after another lookup, that will
fix the problem moving forward.  Thanks for checking by the way.
--
Michael

--jaoouwwPWoQSJZYp
Content-Type: application/pgp-signature; name="signature.asc"

-----BEGIN PGP SIGNATURE-----
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=FocU
-----END PGP SIGNATURE-----

--jaoouwwPWoQSJZYp--