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doc: note witness node behaviour in child node monitoring

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Ian Barwick
2019-05-30 11:50:31 +09:00
parent 45e17223b9
commit 9a0994856a
2 changed files with 993 additions and 8 deletions
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31
doc/repmgrd-automatic-failover.xml
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@@ -408,11 +408,11 @@ INFO: node 3 received notification to rerun promotion candidate election
<para>
When running on the primary node, &repmgrd; can
monitor connections and in particular disconnections by its attached
child nodes (standbys), and optionally execute a custom command
if certain criteria are met (such as the number of attached nodes falling to
zero following a failover to a new primary); this command can be used for
example to &quot;fence&quot; the node and ensure it is isolated from any
applications attempting to access the replication cluster.
child nodes (standbys, and if in use, the witness server), and optionally
execute a custom command if certain criteria are met (such as the number of
attached nodes falling to zero following a failover to a new primary); this
command can be used for example to &quot;fence&quot; the node and ensure it
is isolated from any applications attempting to access the replication cluster.
</para>
<note>
@@ -429,7 +429,7 @@ INFO: node 3 received notification to rerun promotion candidate election
<sect2 id="repmgrd-primary-child-disconnection-monitoring-process">
<title>Standby disconnections monitoring process and criteria</title>
<para>
&repmgrd; monitors attach child nodes and decides
&repmgrd; monitors attached child nodes and decides
whether to invoke the user-defined command based on the following process
and criteria:
<itemizedlist>
@@ -442,6 +442,10 @@ INFO: node 3 received notification to rerun promotion candidate election
the nodes present there against the list of nodes registered with &repmgr; which
should be attached to the primary.
</para>
<para>
If a witness server is in use, &repmgrd; connects to it and checks which upstream node
it is following.
</para>
</listitem>
<listitem>
@@ -450,19 +454,30 @@ INFO: node 3 received notification to rerun promotion candidate election
&repmgrd; notes the time it detected the node's absence, and additionally generates a
<literal>child_node_disconnect</literal> event.
</para>
<para>
If a witness server is in use, and it is no longer following the primary, or not
reachable at all, &repmgrd; notes the time it detected the node's absence, and additionally generates a
<literal>child_node_disconnect</literal> event.
</para>
</listitem>
<listitem>
<para>
If a chile node (standby) which was absent from <literal>pg_stat_replication</literal> reappears,
If a child node (standby) which was absent from <literal>pg_stat_replication</literal> reappears,
&repmgrd; clears the time it detected the node's absence, and additionally generates a
<literal>child_node_reconnect</literal> event.
</para>
<para>
If a witness server is in use, which was previously not reachable or not following the
primary node, has become reachable and is following the primary node, &repmgrd; clears the
time it detected the node's absence, and additionally generates a
<literal>child_node_reconnect</literal> event.
</para>
</listitem>
<listitem>
<para>
If an entirely new child node (standby) is detected, &repmgrd; adds it to its internal list
If an entirely new child node (standby or witness) is detected, &repmgrd; adds it to its internal list
and additionally generates a <literal>child_node_new_connect</literal> event.
</para>
</listitem>