Improve replication connection timeouts.

Rename replication_timeout to wal_sender_timeout, and add a new setting
called wal_receiver_timeout that does the same at the walreceiver side.
There was previously no timeout in walreceiver, so if the network went down,
for example, the walreceiver could take a long time to notice that the
connection was lost. Now with the two settings, both sides of a replication
connection will detect a broken connection similarly.

It is no longer necessary to manually set wal_receiver_status_interval to
a value smaller than the timeout. Both wal sender and receiver now
automatically send a "ping" message if more than 1/2 of the configured
timeout has elapsed, and it hasn't received any messages from the other end.

Amit Kapila, heavily edited by me.

doc/src/sgml/config.sgml

@@ -2236,10 +2236,10 @@ include 'filename'
        </listitem>
       </varlistentry>
 
-     <varlistentry id="guc-replication-timeout" xreflabel="replication_timeout">
-      <term><varname>replication_timeout</varname> (<type>integer</type>)</term>
+     <varlistentry id="guc-wal-sender-timeout" xreflabel="wal_sender_timeout">
+      <term><varname>wal_sender_timeout</varname> (<type>integer</type>)</term>
       <indexterm>
-       <primary><varname>replication_timeout</> configuration parameter</primary>
+       <primary><varname>wal_sender_timeout</> configuration parameter</primary>
       </indexterm>
       <listitem>
        <para>
@@ -2251,12 +2251,6 @@ include 'filename'
         the <filename>postgresql.conf</> file or on the server command line.
         The default value is 60 seconds.
        </para>
-       <para>
-        To prevent connections from being terminated prematurely,
-        <xref linkend="guc-wal-receiver-status-interval">
-        must be enabled on the standby, and its value must be less than the
-        value of <varname>replication_timeout</>.
-       </para>
       </listitem>
      </varlistentry>
 
@@ -2474,11 +2468,6 @@ include 'filename'
        the <filename>postgresql.conf</> file or on the server command line.
        The default value is 10 seconds.
       </para>
-      <para>
-       When <xref linkend="guc-replication-timeout"> is enabled on a sending server,
-       <varname>wal_receiver_status_interval</> must be enabled, and its value
-       must be less than the value of <varname>replication_timeout</>.
-      </para>
       </listitem>
      </varlistentry>
 
@@ -2507,6 +2496,25 @@ include 'filename'
       </listitem>
      </varlistentry>
 
+     <varlistentry id="guc-wal-receiver-timeout" xreflabel="wal_receiver_timeout">
+      <term><varname>wal_receiver_timeout</varname> (<type>integer</type>)</term>
+      <indexterm>
+       <primary><varname>wal_receiver_timeout</> configuration parameter</primary>
+      </indexterm>
+      <listitem>
+       <para>
+        Terminate replication connections that are inactive longer
+        than the specified number of milliseconds. This is useful for
+        the receiving standby server to detect a primary node crash or network
+        outage.
+        A value of zero disables the timeout mechanism.  This parameter
+        can only be set in
+        the <filename>postgresql.conf</> file or on the server command line.
+        The default value is 60 seconds.
+       </para>
+      </listitem>
+     </varlistentry>
+
      </variablelist>
     </sect2>
    </sect1>

doc/src/sgml/release-9.1.sgml

@@ -3322,7 +3322,7 @@
      <listitem>
       <para>
        Add
-       <link linkend="guc-replication-timeout"><varname>replication_timeout</></link>
+       <varname>replication_timeout</>
        setting (Fujii Masao, Heikki Linnakangas)
       </para>