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doc: improve BDR failover documentation

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Ian Barwick
2018-02-05 13:25:49 +09:00
parent c19e7f1025
commit 3b823396eb
1 changed files with 33 additions and 20 deletions
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53
doc/repmgrd-bdr.sgml
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@@ -174,17 +174,13 @@
<para>
Key to "failover" execution is the <literal>event_notification_command</literal>,
which is a user-definable script specified in <filename>repmpgr.conf</filename>
and which should reconfigure the proxy server/ connection pooler to point
to the other, still-active node.
and which can use a &repmgr; <link linkend="event-notifications">event notification</link>
to reconfigure the proxy server / connection pooler so it points to the other, still-active node.
Details of the event will be passed as parameters to the script.
</para>
<para>
Each time &repmgr; (or <application>repmgrd</application>) records an event,
it can optionally execute the script defined in
<literal>event_notification_command</literal> to take further action;
details of the event will be passed as parameters.
</para>
<para>
Following placeholders are available to the script:
Following parameter placeholders are available for the script definition in <filename>repmpgr.conf</filename>;
these will be replaced with the appropriate value when the script is executed:
</para>
<variablelist>
@@ -231,20 +227,35 @@
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>%c</option></term>
<listitem>
<para>
conninfo string of the next available node (<varname>bdr_failover</varname>)
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>%a</option></term>
<listitem>
<para>
name of the next available node (<varname>bdr_failover</varname>)
</para>
</listitem>
</varlistentry>
</variablelist>
<para>
Note that <literal>%c</literal> and <literal>%a</literal> will only be provided during
<varname>bdr_failover</varname> events, which is what is of interest here.
Note that <literal>%c</literal> and <literal>%a</literal> are only provided with
particular failover events, in this case <varname>bdr_failover</varname>.
</para>
<para>
The provided sample script (`scripts/bdr-pgbouncer.sh`) is configured like
this:
The provided sample script (`scripts/bdr-pgbouncer.sh`) is configured as follows:
<programlisting>
event_notification_command='/path/to/bdr-pgbouncer.sh %n %e %s "%c" "%a"'</programlisting>
</para>
<para>
and parses the configures parameters like this:
and parses the placeholder parameters like this:
<programlisting>
NODE_ID=$1
EVENT_TYPE=$2
@@ -252,12 +263,14 @@
NEXT_CONNINFO=$4
NEXT_NODE_NAME=$5</programlisting>
</para>
<para>
The script also contains some hard-coded values about the <application>PgBouncer</application>
configuration for both nodes; these will need to be adjusted for your local environment
(ideally the scripts would be maintained as templates and generated by some
kind of provisioning system).
</para>
<note>
<para>
The sample script also contains some hard-coded values for the <application>PgBouncer</application>
configuration for both nodes; these will need to be adjusted for your local environment
(ideally the scripts would be maintained as templates and generated by some
kind of provisioning system).
</para>
</note>
<para>
The script performs following steps: