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<chapter>
	<title>&adminguide;</title>
	
	<section>
	<title>Overview</title>
	<para>
	This is a module for fast number portability handling. The client is this module
	and the server exists in the /utils/pdbt directory.
	The PDB module and server supports load-balancing and aggressive timeouts.
	Normally it does not need more than a few ms to query the remote server and return
	the reply to the configuration script.
	</para>
	<para>
	The pdb module allows &kamailio; to send queries to a list of servers
  	and store the answer in an AVP. The idea is to ask all servers in
  	parallel and use the first answer, that comes back. A timeout for the
	query can be defined in milliseconds. The queying can be activated and
  	deactivated using FIFO commands.
	</para>
	<para>
    More about the new communication protocol between this module and pdb_server
    can be found in utils/pdbt/docs/network_protocol.txt. The current version is 1.
	</para>
	</section>

	<section>
		<title>Dependencies</title>
		<section>
			<title>&kamailio; Modules</title>
			<para>
			The module depends on the following modules (in the other words 
			the listed modules must be loaded before this module):
			</para>
			<itemizedlist>
			<listitem>
				<para><emphasis>none</emphasis></para>
			</listitem>
			</itemizedlist>
		</section>
		<section>
			<title>External Libraries or Applications</title>
			<para>
			The following libraries or applications must be installed 
			before running &kamailio; with this module loaded:
			</para>
			<itemizedlist>
				<listitem>
				<para><emphasis>The PDB server</emphasis></para>
				</listitem>
			</itemizedlist>
		</section>
	</section>


	<section>
	<title>Parameters</title>
    <section>
	    <title><varname>timeout</varname> (integer)</title>
	    <para>
			This is the timeout in milliseconds for the pdb_query function.
	    </para>
	    <para>
		    <emphasis>
			    Default value is <quote>50</quote>.
		    </emphasis>
	    </para>
	    <example>
		    <title>Set <varname>timeout</varname> parameter</title>
		    <programlisting format="linespecific">
...
modparam("pdb", "timeout", 10)
...
		    </programlisting>
	    </example>
    </section>
    <section>
	    <title><varname>server</varname> (string)</title>
	    <para>
			This is the list of servers to be used by the pdb_query function.
      Queries will be sent in parallel to all servers configured in this list.
			This parameter is mandatory.
	    </para>
	    <example>
		    <title>Set <varname>server</varname> parameter</title>
		    <programlisting format="linespecific">
...
modparam("pdb", "server", "localhost:10001,host.name:10001,192.168.1.7:10002")
...
		    </programlisting>
	    </example>
    </section>
	</section>
	<section>
		<title>Functions</title>
		<section>
	    <title>
				<function moreinfo="none">pdb_query (string query, string dstavp)</function>
	    </title>
	    <para>
				Sends the query string to all configured servers and stores the answer in
				dstavp. If it takes more than the configured timeout, false is returned.
				
				Pseudo-variables or AVPs can be used for the query string.
				
				The answer must consist of the null terminated query string followed by
				a two byte integer value in network byte order. The integer value will
				be stored in the given AVP.
	    </para>
			<example>
				<title><function>pdb_query</function> usage</title>
				<programlisting format="linespecific">
...
# query external service for routing information
if (!pdb_query("$rU", "$avp(i:82)"))
  $avp(i:82) = 0; # default routing
}
cr_route("$avp(i:82)", "$rd", "$rU", "$rU", "call_id");
...
				</programlisting>
			</example>
		</section>
	</section>
	<section>
		<title><acronym>MI</acronym> Commands</title>
		<section>
	    <title>
				<function moreinfo="none">pdb_status</function>
	    </title>
	    <para>
				Prints the status of the module.
				This can either be "active" or "deactivated".
	    </para>
			<example>
				<title><function>pdb_status</function> usage</title>
				<programlisting format="linespecific">
...
&ctltool; fifo pdb_status
...
				</programlisting>
	    </example>
		</section>
		<section>
	    <title>
				<function moreinfo="none">pdb_activate</function>
	    </title>
	    <para>
				Activates the module. This is the default after loading the module.
	    </para>
			<example>
				<title><function>pdb_activate</function> usage</title>
				<programlisting format="linespecific">
...
&ctltool; fifo pdb_activate
...
				</programlisting>
	    </example>
		</section>
		<section>
	    <title>
				<function moreinfo="none">pdb_deactivate</function>
	    </title>
	    <para>
				Deactivates the module. No more queries are performed until it is
				activated again. As long as the module is deactivated, the
				pdb_query function will return -1.
	    </para>
			<example>
				<title><function>pdb_deactivate</function> usage</title>
				<programlisting format="linespecific">
...
&ctltool; fifo pdb_deactivate
...
				</programlisting>
	    </example>
		</section>
	</section>
</chapter>
