"standby register/follow": provide primary node details for event notifications

For events generated by these commands, it may be useful to know details
of the primary node. This makes following additional parameters available
to event notification scripts:

- %p: node ID of the primary
- %a: node name of the primary
- %c: conninfo string for the primary

Implements GitHub #375

doc/event-notifications.sgml

@@ -37,7 +37,7 @@
   <filename>repmgr.conf</filename>.
  </para>
  <para>
-  This parameter accepts the following format placeholders:
+  The following format placeholders are provided for all event notifications:
  </para>
 
  <variablelist>
@@ -84,18 +84,8 @@
     </para>
    </listitem>
   </varlistentry>
-
-
-  <varlistentry>
-   <term><option>%p</option></term>
-   <listitem>
-    <para>
-     node ID of the demoted primary (<xref linkend="repmgr-standby-switchover"> only)
-    </para>
-   </listitem>
-  </varlistentry>
-
  </variablelist>
+
  <para>
   The values provided for <literal>%t</literal> and <literal>%d</literal>
   will probably contain spaces, so should be quoted in the provided command
@@ -104,34 +94,60 @@
     event_notification_command='/path/to/some/script %n %e %s "%t" "%d"'
   </programlisting>
  </para>
+
  <para>
-  Additionally the following format placeholders are available for the event
-  type <varname>bdr_failover</varname> and optionally <varname>bdr_recovery</varname>:
+   The following parameters are provided for a subset of event notifications:
  </para>
+
  <variablelist>
+  <varlistentry>
+   <term><option>%p</option></term>
+   <listitem>
+    <para>
+     node ID of the current primary (<xref linkend="repmgr-standby-register"> and <xref linkend="repmgr-standby-follow">)
+    </para>
+    <para>
+     node ID of the demoted primary (<xref linkend="repmgr-standby-switchover"> only)
+    </para>
+   </listitem>
+  </varlistentry>
   <varlistentry>
    <term><option>%c</option></term>
    <listitem>
     <para>
-     conninfo string of the next available node
+     <literal>conninfo</literal> string of the primary node
+     (<xref linkend="repmgr-standby-register"> and <xref linkend="repmgr-standby-follow">)
+    </para>
+    <para>
+      <literal>conninfo</literal> string of the next available node
+      (<varname>bdr_failover</varname> and  <varname>bdr_recovery</varname>)
     </para>
    </listitem>
   </varlistentry>
+
   <varlistentry>
    <term><option>%a</option></term>
    <listitem>
     <para>
-     name of the next available node
+     name of the current primary node (<xref linkend="repmgr-standby-register"> and <xref linkend="repmgr-standby-follow">)
+    </para>
+    <para>
+     name of the next available node (<varname>bdr_failover</varname> and  <varname>bdr_recovery</varname>)
     </para>
    </listitem>
   </varlistentry>
+
  </variablelist>
+
  <para>
-  These should always be quoted.
+  The values provided for <literal>%c</literal> and <literal>%a</literal>
+  will probably contain spaces, so should always be quoted.
  </para>
+
  <para>
   By default, all notification types will be passed to the designated script;
-  the notification types can be filtered to explicitly named ones:
+  the notification types can be filtered to explicitly named ones using the
+  <varname>event_notifications</varname> parameter:
 
   <itemizedlist spacing="compact" mark="bullet">
 
@@ -219,6 +235,7 @@
 
   </itemizedlist>
  </para>
+
  <para>
   Note that under some circumstances (e.g. when no replication cluster primary
   could be located), it will not be possible to write an entry into the

doc/repmgr-standby-follow.sgml

@@ -87,9 +87,14 @@
     <para>
       A <literal>standby_follow</literal> <link linkend="event-notifications">event notification</link> will be generated.
     </para>
+    <para>
+      If provided, &repmgr; will subsitute the placeholders <literal>%p</literal> with the node ID of the primary
+      being followed, <literal>%c</literal> with its <literal>conninfo</literal> string, and
+      <literal>%a</literal> with its node name.
+    </para>
   </refsect1>
 
- <refsect1>
+  <refsect1>
     <title>See also</title>
     <para>
      <xref linkend="repmgr-node-rejoin">

doc/repmgr-standby-register.sgml

@@ -105,6 +105,12 @@
       standby.
     </para>
 
+    <para>
+      If provided, &repmgr; will subsitute the placeholders <literal>%p</literal> with the node ID of the
+      primary node, <literal>%c</literal> with its <literal>conninfo</literal> string, and
+      <literal>%a</literal> with its node name.
+    </para>
+
   </refsect1>
 
 </refentry>