From: Jesper Pedersen <jesper.pedersen@redhat.com>
To: Laurenz Albe <laurenz.albe@cybertec.at>
To: Michael Paquier <michael@paquier.xyz>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: pg_receivewal documentation
Date: Tue, 16 Jul 2019 13:03:12 -0400
Message-ID: <65c3ecdf-8995-34cb-83c4-50068877e632@redhat.com> (raw)
In-Reply-To: <ebed4b9043b222d486ea3f0e44e7dcd242a80781.camel@cybertec.at>
References: <20190710142421.GA28387@alvherre.pgsql>
<54779de5-f922-c0cf-629d-b582eded7265@redhat.com>
<20190716050555.GA1439@paquier.xyz>
<ebed4b9043b222d486ea3f0e44e7dcd242a80781.camel@cybertec.at>
Hi,
On 7/16/19 12:28 PM, Laurenz Albe wrote:
>> This is not true in all cases as since 9.6 it is possible to specify
>> multiple synchronous standbys. So if for example pg_receivewal and
>> another synchronous standby are set in s_s_names and that the number
>> of a FIRST (priority-based) or ANY (quorum set) is two, then the same
>> issue exists, but this documentation is incorrect. I think that we
>> should have a more extensive wording here, like "if pg_receivewal is
>> part of a quorum-based or priority-based set of synchronous standbys."
>
> I think this would be overly complicated.
> The wording above seems to cover the priority-based base sufficiently
> in my opinion.
> Maybe a second sentence with more detail would be better:
>
> ... must not be set to <literal>remote_apply</literal> if
> <application>pg_receivewal</application> is the only synchronous standby.
> Similarly, if <application>pg_receivewal</application> is part of
> a quorum-based set of synchronous standbys, it won't count towards
> the quorum if <xref linkend="guc-synchronous-commit"/> is set to
> <literal>remote_apply</literal>.
>
Here is the patch for that.
Best regards,
Jesper
Attachments:v5_pgreceivewal-doc.patch (text/x-patch, 1.6K) download
From 4fb28d6fe08ddea5a9740c9a81e8e00b94283d78 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
Authors: Álvaro Herrera, Laurenz Albe and Jesper Pedersen
Review-by: Álvaro Herrera, Laurenz Albe and Jesper Pedersen
---
doc/src/sgml/ref/pg_receivewal.sgml | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/doc/src/sgml/ref/pg_receivewal.sgml b/doc/src/sgml/ref/pg_receivewal.sgmlindex 0506120c00..03b20ecd38 100644--- a/doc/src/sgml/ref/pg_receivewal.sgml+++ b/doc/src/sgml/ref/pg_receivewal.sgml@@ -207,6 +207,18 @@ PostgreSQL documentation
server as a synchronous standby, to ensure that timely feedback is
sent to the server.
</para>
++ <para>+ Note that while WAL will be flushed with this setting,+ <application>pg_receivewal</application> never applies it, so+ <xref linkend="guc-synchronous-commit"/> must not be set to+ <literal>remote_apply</literal> if <application>pg_receivewal</application>+ is the only synchronous standby. Similarly, if+ <application>pg_receivewal</application> is part of a quorum-based+ set of synchronous standbys, it won't count towards the quorum if+ <xref linkend="guc-synchronous-commit"/> is set to+ <literal>remote_apply</literal>.+ </para>
</listitem>
</varlistentry>
--
2.21.0
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-hackers@postgresql.org
Cc: jesper.pedersen@redhat.com, laurenz.albe@cybertec.at, michael@paquier.xyz, alvherre@2ndquadrant.com
Subject: Re: pg_receivewal documentation
In-Reply-To: <65c3ecdf-8995-34cb-83c4-50068877e632@redhat.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox