Add support TCP user timeout in libpq and the backend server

Similarly to the set of parameters for keepalive, a connection parameter
for libpq is added as well as a backend GUC, called tcp_user_timeout.

Increasing the TCP user timeout is useful to allow a connection to
survive extended periods without end-to-end connection, and decreasing
it allows application to fail faster.  By default, the parameter is 0,
which makes the connection use the system default, and follows a logic
close to the keepalive parameters in its handling.  When connecting
through a Unix-socket domain, the parameters have no effect.

Author: Ryohei Nagaura
Reviewed-by: Fabien Coelho, Robert Haas, Kyotaro Horiguchi, Kirk
Jamison, Mikalai Keida, Takayuki Tsunakawa, Andrei Yahorau
Discussion: https://postgr.es/m/EDA4195584F5064680D8130B1CA91C45367328@G01JPEXMBYT04

2 files changed, 39 insertions, 0 deletions

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index bc1d0f7bfae..d2da1abe618 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -939,6 +939,31 @@ include_dir 'conf.d'
       </listitem>
      </varlistentry>
 
+     <varlistentry id="guc-tcp-user-timeout" xreflabel="tcp_user_timeout">
+      <term><varname>tcp_user_timeout</varname> (<type>integer</type>)
+      <indexterm>
+       <primary><varname>tcp_user_timeout</varname> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        Specifies the number of milliseconds that transmitted data may
+        remain unacknowledged before a connection is forcibly closed.
+        A value of 0 uses the system default.
+        This parameter is supported only on systems that support
+        <symbol>TCP_USER_TIMEOUT</symbol>; on other systems, it must be zero.
+        In sessions connected via a Unix-domain socket, this parameter is
+        ignored and always reads as zero. 
+       </para>
+       <note>
+        <para>
+         This parameter is not supported on Windows and on Linux version
+         2.6.36 or older.
+        </para>
+       </note>
+      </listitem>
+     </varlistentry>
+
      </variablelist>
      </sect2>
 
diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index 924b7ce50e1..fe833aa6260 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -1249,6 +1249,20 @@ postgresql://%2Fvar%2Flib%2Fpostgresql/dbname
       </listitem>
      </varlistentry>
 
+     <varlistentry id="libpq-tcp-user-timeout" xreflabel="libpq_tcp_user_timeout">
+      <term><literal>tcp_user_timeout</literal></term>
+      <listitem>
+       <para>
+        Controls the number of milliseconds that transmitted data may
+        remain unacknowledged before a connection is forcibly closed.
+        A value of zero uses the system default. This parameter is
+        ignored for connections made via a Unix-domain socket.
+        It is only supported on systems where <symbol>TCP_USER_TIMEOUT</symbol>
+        is available; on other systems, it has no effect.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="libpq-connect-tty" xreflabel="tty">
       <term><literal>tty</literal></term>
       <listitem>