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Enable pg_rewind to be used with PostgreSQL 9.3/9.4

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pg_rewind is not part of the core distribution for those, but we
provided support in repmgr 3.3 so should extend it to repmgr 4.

Note that there is no check in place whether the pg_rewind binary
exists, so it's up to the user to ensure it's present.

Addresses GitHub #413.
This commit is contained in:
Ian Barwick
2018-03-30 16:04:00 +09:00
committed by Ian Barwick
parent 5e4bdb5a1b
commit 3ccf1cf182
9 changed files with 180 additions and 94 deletions
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7
doc/repmgr-standby-switchover.sgml
View File

@@ -84,11 +84,14 @@
</varlistentry>
<varlistentry>
<term><option>--force-rewind</option></term>
<term><option>--force-rewind[=/path/to/pg_rewind]</option></term>
<listitem>
<para>
Use <application>pg_rewind</application> to reintegrate the old primary if necessary
(PostgreSQL 9.5 and later).
(and the prerequisites for using <application>pg_rewind</application> are met).
If using PostgreSQL 9.3 or 9.4, and the <application>pg_rewind</application>
binary is not installed in the PostgreSQL <filename>bin</filename> directory,
provide its full path. For more details see also <xref linkend="switchover-pg-rewind">.
</para>
</listitem>
</varlistentry>

40
doc/switchover.sgml
View File

@@ -179,6 +179,46 @@
</simpara>
</note>
<sect2 id="switchover-pg-rewind" xreflabel="Switchover and pg_rewind">
<title>Switchover and pg_rewind</title>
<para>
If the demotion candidate does not shut down smoothly or cleanly, there's a risk it
will have a slightly divergent timeline and will not be able to attach to the new
primary. To fix this situation without needing to reclone the old primary, it's
possible to use the <application>pg_rewind</application> utility, which will usually be
able to resync the two servers.
</para>
<para>
To have &repmgr; execute <application>pg_rewind</application> if it detects this
situation after promoting the new primary, add the <option>--force-rewind</option>
option.
</para>
<note>
<simpara>
If &repmgr; detects a situation where it needs to execute <application>pg_rewind</application>,
it will execute a <literal>CHECKPOINT</literal> on the new primary before executing
<application>pg_rewind</application>.
</simpara>
</note>
<para>
For more details on <application>pg_rewind</application>, see:
<ulink url="https://www.postgresql.org/docs/current/static/app-pgrewind.html">https://www.postgresql.org/docs/current/static/app-pgrewind.html</ulink>.
</para>
<para>
<application>pg_rewind</application> has been part of the core PostgreSQL distribution since
version 9.5. Users of versions 9.3 and 9.4 will need to manually install; source code available here:
<ulink url="https://github.com/vmware/pg_rewind">https://github.com/vmware/pg_rewind</ulink>.
If the <application>pg_rewind</application>
binary is not installed in the PostgreSQL <filename>bin</filename> directory, provide
its full path on the demotion candidate with <option>--force-rewind</option>.
</para>
<para>
Note that building the 9.3/9.4 version of <application>pg_rewind</application> requires the PostgreSQL
source code. Also, PostgreSQL 9.3 does not provide <varname>wal_log_hints</varname>,
meaning data checksums must have been enabled when the database was initialized.
</para>
</sect2>
</sect1>