Support configurable eventlog application names on Windows

This allows different instances to use the eventlog with different
identifiers, by setting the event_source GUC, similar to how
syslog_ident works.

Original patch by MauMau, heavily modified by Magnus Hagander

doc/src/sgml/config.sgml

@@ -3037,6 +3037,14 @@ local0.*    /var/log/postgresql
          to the  <application>syslog</application> daemon's configuration file
          to make it work.
         </para>
+        <para>
+         On Windows, when you use the <literal>eventlog</literal>
+         option for <varname>log_destination</>, you should
+         register an event source and its library with the operating
+         system so that the Windows Event Viewer can display event
+         log messages cleanly.
+         See <xref linkend="event-log-registration"> for details.
+        </para>
        </note>
       </listitem>
      </varlistentry>
@@ -3287,6 +3295,23 @@ local0.*    /var/log/postgresql
        </listitem>
       </varlistentry>
 
+     <varlistentry id="guc-event-source" xreflabel="event_source">
+      <term><varname>event_source</varname> (<type>string</type>)</term>
+      <indexterm>
+       <primary><varname>event_source</> configuration parameter</primary>
+      </indexterm>
+      <listitem>
+       <para>
+        When logging to <application>event log</> is enabled, this parameter
+        determines the program name used to identify
+        <productname>PostgreSQL</productname> messages in
+        the log. The default is <literal>PostgreSQL</literal>.
+        This parameter can only be set in the <filename>postgresql.conf</>
+        file or on the server command line.
+       </para>
+      </listitem>
+     </varlistentry>
+
       </variablelist>
     </sect2>
      <sect2 id="runtime-config-logging-when">

doc/src/sgml/installation.sgml

@@ -1551,19 +1551,6 @@ PostgreSQL, contrib and HTML documentation successfully made. Ready to install.
   </step>
   </procedure>
 
-  <formalpara>
-   <title>Registering <application>eventlog</> on <systemitem
-   class="osname">Windows</>:</title>
-   <para>
-    To register a <systemitem class="osname">Windows</> <application>eventlog</>
-    library with the operating system, issue this command after installation:
-<screen>
-<userinput>regsvr32 <replaceable>pgsql_library_directory</>/pgevent.dll</>
-</screen>
-    This creates registry entries used by the event viewer.
-   </para>
-  </formalpara>
-
   <formalpara>
    <title>Uninstallation:</title>
    <para>

doc/src/sgml/runtime.sgml

@@ -2295,4 +2295,50 @@ ssh -L 63333:db.foo.com:5432 joe@shell.foo.com
 
  </sect1>
 
+ <sect1 id="event-log-registration">
+  <title>Registering <application>Event Log</> on <systemitem
+  class="osname">Windows</></title>
+
+  <indexterm zone="event-log-registration">
+   <primary>event log</primary>
+   <secondary>event log</secondary>
+  </indexterm>
+
+  <para>
+   To register a <systemitem class="osname">Windows</>
+   <application>event log</> library with the operating system,
+   issue this command:
+<screen>
+<userinput>regsvr32 <replaceable>pgsql_library_directory</>/pgevent.dll</>
+</screen>
+   This creates registry entries used by the event viewer, under the default
+   event source named <literal>PostgreSQL</literal>.
+  </para>
+
+  <para>
+   To specify a different event source name (see
+   <xref linkend="guc-event-source">), use the <literal>/n</literal>
+   and <literal>/i</literal> options:
+<screen>
+<userinput>regsvr32 /n /i:<replaceable>event_source_name</> <replaceable>pgsql_library_directory</>/pgevent.dll</>
+</screen>
+  </para>
+
+  <para>
+   To unregister the <application>event log</> library from
+   the operating system, issue this command:
+<screen>
+<userinput>regsvr32 /u [/i:<replaceable>event_source_name</>] <replaceable>pgsql_library_directory</>/pgevent.dll</>
+</screen>
+  </para>
+
+  <note>
+   <para>
+    To enable event logging in the database server, modify
+    <xref linkend="guc-log-destination"> to include
+    <literal>eventlog</literal> in <filename>postgresql.conf</filename>.
+   </para>
+  </note>
+ </sect1>
+
 </chapter>