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Fix handling of upstream node change check

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repmgrd has a check to see if the upstream node has unexpectedly
changed, e.g. if the repmgrd service is paused and the PostgreSQL
instance has been pointed to another node.

However this check was relying on the node record on the local node
being up-to-date, which may not be the case immediately after a
failover, when the node is still replaying records updated prior
to the node's own record being updated. In this case it will
mistakenly assume the node is following the original primary
and attempt to restart monitoring, which will fail as the original
primary is no longer available.

To prevent this, we check against the node's record on the upstream
node.

Addresses issue noted in GitHub #587 and #588.
This commit is contained in:
Ian Barwick
2019-10-14 09:31:47 +09:00
parent 4aaa24a5f8
commit 2304584679
3 changed files with 56 additions and 9 deletions
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26
doc/appendix-release-notes.xml
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@@ -228,8 +228,34 @@ conninfo='host=node1 user=repmgr dbname=repmgr connect_timeout=2'</programlistin
or <literal>pg_monitor</literal> are permitted to do this as well.
</para>
</listitem>
<listitem>
<para>
&repmgrd;: Fix handling of upstream node change check.
</para>
<para>
&repmgrd; has a check to see if the upstream node has unexpectedly
changed, e.g. if the repmgrd service is paused and the PostgreSQL
instance has been pointed to another node.
</para>
<para>
However this check was relying on the node record on the local node
being up-to-date, which may not be the case immediately after a
failover, when the node is still replaying records updated prior
to the node's own record being updated. In this case it will
mistakenly assume the node is following the original primary
and attempt to restart monitoring, which will fail as the original
primary is no longer available.
</para>
<para>
To prevent this, the node's record on the upstream node is checked
to see if the reported upstream <literal>node_id</literal> matches
the expected <literal>node_id</literal>. GitHub #587/#588.
</para>
</listitem>
</itemizedlist>
</para>
</sect2>
</sect1>