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From: Jesper Pedersen <jesper.pedersen@redhat.com>
To: Michael Paquier <michael@paquier.xyz>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: Laurenz Albe <laurenz.albe@cybertec.at>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: pg_receivewal documentation
Date: Tue, 23 Jul 2019 08:00:41 -0400
Message-ID: <72d2d628-eff9-94dc-8ced-0869bfda4e80@redhat.com> (raw)
In-Reply-To: <20190723000820.GA2059@paquier.xyz>
References: <20190710142421.GA28387@alvherre.pgsql>
	<54779de5-f922-c0cf-629d-b582eded7265@redhat.com>
	<20190716050555.GA1439@paquier.xyz>
	<ebed4b9043b222d486ea3f0e44e7dcd242a80781.camel@cybertec.at>
	<65c3ecdf-8995-34cb-83c4-50068877e632@redhat.com>
	<20190717013835.GA2130@paquier.xyz>
	<CA+TgmoY-8im5GHnSf1zih8t66DOcy7CO+i_p01LbP6ck+Unhpg@mail.gmail.com>
	<20190722014851.GC1757@paquier.xyz>
	<9fea76ce-6912-c262-6f64-2b7c4496be65@redhat.com>
	<20190723000820.GA2059@paquier.xyz>

Hi,

On 7/22/19 8:08 PM, Michael Paquier wrote:
>> +   <xref linkend="guc-synchronous-commit"/> to something other than
> 
> Looks fine to me.  Just a tiny nit.  For the second reference to
> synchronous_commit, I would change the link to a <varname> markup.

Sure.

Best regards,
  Jesper

Attachments:

v10_pgreceivewal-doc.patch (text/x-patch, 1.8K) download From f6c5e9128e0779f928d94bf9bcc8813bf03150f0 Mon Sep 17 00:00:00 2001 From: jesperpedersen <jesper.pedersen@redhat.com> Date: Tue, 9 Jul 2019 13:14:25 -0400 Subject: [PATCH] Highlight that pg_receivewal doesn't apply WAL, and as such synchronous-commit needs to be remote_write or lower. MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Author: Robert Haas Review-by: Michael Paquier, Álvaro Herrera, Laurenz Albe and Jesper Pedersen --- doc/src/sgml/ref/pg_receivewal.sgml | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/doc/src/sgml/ref/pg_receivewal.sgml b/doc/src/sgml/ref/pg_receivewal.sgml index 0506120c00..a7536bed92 100644 --- a/doc/src/sgml/ref/pg_receivewal.sgml +++ b/doc/src/sgml/ref/pg_receivewal.sgml @@ -52,7 +52,15 @@ PostgreSQL documentation Unlike the WAL receiver of a PostgreSQL standby server, <application>pg_receivewal</application> by default flushes WAL data only when a WAL file is closed. The option <option>--synchronous</option> must be specified to flush WAL data - in real time. + in real time. Since <application>pg_receivewal</application> does not apply WAL, + you should not allow it to become a synchronous standby when + <xref linkend="guc-synchronous-commit"/> equals <literal>remote_apply</literal>. + If it does, it will appear to be a standby which never catches up, + which may cause commits to block. To avoid this, you should either + configure an appropriate value for <xref linkend="guc-synchronous-standby-names"/>, or + specify an <varname>application_name</varname> for + <application>pg_receivewal</application> that does not match it, or change the value of + <varname>synchronous_commit</varname> to something other than <literal>remote_apply</literal>. </para> <para> -- 2.21.0

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