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From: Peter Eisentraut <peter_e@gmx.net>
To: pgsql-docs <pgsql-docs@postgresql.org>
Subject: Re: obsolete pg_receivexlog note?
Date: Wed, 05 Nov 2014 16:42:02 -0500
Message-ID: <545A99AA.5020107@gmx.net> (raw)
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References: <54454F47.50407@gmx.net>
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On 10/20/14 2:07 PM, Peter Eisentraut wrote:
> The reference page for pg_receivexlog
> (http://www.postgresql.org/docs/9.4/static/app-pgreceivexlog.html) has
> this note:
> 
> """
> When using pg_receivexlog instead of archive_command, the server will
> continue to recycle transaction log files even if the backups are not
> properly archived, since there is no command that fails. This can be
> worked around by having an archive_command that fails when the file has
> not been properly archived yet, for example:
> 
> archive_command = 'sleep 5 && test -f /mnt/server/archivedir/%f'
> The initial timeout is necessary because pg_receivexlog works using
> asynchronous replication and can therefore be slightly behind the master.
> """
> 
> ISTM that this should be replaced with something to the effect of, if
> you are using pg_receivexlog instead of archive_command, you had better
> use slots.

Here is a patch.

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Attachments:

pg-receivexlog-notes.patch (application/x-patch, 1.4K) download
diff --git a/doc/src/sgml/ref/pg_receivexlog.sgml b/doc/src/sgml/ref/pg_receivexlog.sgml
index 2ab392e..f90b61c 100644
--- a/doc/src/sgml/ref/pg_receivexlog.sgml
+++ b/doc/src/sgml/ref/pg_receivexlog.sgml
@@ -324,17 +324,12 @@ <title>Notes</title>
 
   <para>
    When using <application>pg_receivexlog</application> instead of
-   <xref linkend="guc-archive-command">, the server will continue to
-   recycle transaction log files even if the backups are not properly
-   archived, since there is no command that fails. This can be worked
-   around by having an <xref linkend="guc-archive-command"> that fails
-   when the file has not been properly archived yet, for example:
-<programlisting>
-archive_command = 'sleep 5 &amp;&amp; test -f /mnt/server/archivedir/%f'
-</programlisting>
-   The initial timeout is necessary because
-   <application>pg_receivexlog</application> works using asynchronous
-   replication and can therefore be slightly behind the master.
+   <xref linkend="guc-archive-command"> as the main WAL backup method, it is
+   strongly recommended to use replication slots.  Otherwise, the server is
+   free to recycle or remove transaction log files before they are backed up,
+   because it does not have any information, either
+   from <xref linkend="guc-archive-command"> or the replication slots, about
+   how far the WAL stream has been archived.
   </para>
 
  </refsect1>

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  Subject: Re: obsolete pg_receivexlog note?
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