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<!-- Module User's Guide -->

<chapter>
	
	<title>&adminguide;</title>
	
	<section>
	<title>Overview</title>
	<para>
		This module provides asynchronous operations for handling SIP requests
		in the configuration file.
	</para>
	<para>
		Async uses t_suspend() and t_continue() from the TM and TMX modules.
	</para>
	<para>
		Note that after invoking the asynchronous operation, the processing
		will continue later in another application process. Therefore variables 
		stored in private memory should not be used, try to use shared memory if you
		want to get values after the processing is resumed (e.g., $avp(...),
		$xavp(...), $shv(...), htable $sht(...)).
	</para>
	</section>

	<section>
	<title>Dependencies</title>
	<section>
		<title>&kamailio; Modules</title>
		<para>
		The following modules must be loaded before this module:
			<itemizedlist>
			<listitem>
			<para>
				<emphasis>tm</emphasis> - transaction management.
			</para>
			</listitem>
			<listitem>
			<para>
				<emphasis>tmx</emphasis> - transaction management extensions.
			</para>
			</listitem>
			</itemizedlist>
		</para>
	</section>
	<section>
		<title>External Libraries or Applications</title>
		<para>
		The following libraries or applications must be installed before running
		&kamailio; with this module loaded:
			<itemizedlist>
			<listitem>
			<para>
				<emphasis>None</emphasis>
			</para>
			</listitem>
			</itemizedlist>
		</para>
	</section>
	</section>
	<section>
	<title>Parameters</title>
	<section>
		<title><varname>workers</varname> (int)</title>
		<para>
			Number of worker processes to be started to handle the asynchronous
			tasks for async_route() and async_sleep(). 
		</para>
		<para>
		<emphasis>
			Default value is 1.
		</emphasis>
		</para>
		<example>
		<title>Set <varname>workers</varname> parameter</title>
		<programlisting format="linespecific">
...
modparam("async", "workers", 2)
...
</programlisting>
		</example>
	</section>
	</section>

	<section>
	<title>Functions</title>
	<section id="async.f.async_route">
	    <title>
		<function moreinfo="none">async_route(routename, seconds)</function>
	    </title>
	    <para>
		Simulate a sleep of 'seconds' and then continue the processing of the SIP
		request with the route[routename]. In case of internal errors, the
		function returns false, otherwise the function exits the execution of
		the script at that moment (return 0 behaviour).
		</para>
		<para>
		The routename parameter can be a static string or a dynamic string
		value with config variables.
		</para>
		<para>
		The sleep parameter represent the number of seconds to suspend the
		processing of a SIP request. Maximum value is 100. The parameter can be
		a static integer or a variable holding an integer.
		</para>
		<para>
		Since the SIP request handling is resumed in another process,
		the config file execution state is practically lost. Therefore beware
		that the execution of config after resume will end once the
		route[routename] is finished.
		</para>
		<para>
		This function can be used from REQUEST_ROUTE.
		</para>
		<example>
		<title><function>async_route</function> usage</title>
		<programlisting format="linespecific">
...
async_route("RESUME", "4");
...
route[RESUME] {
   send_reply("404", "Not found");
   exit;
}
...
</programlisting>
	    </example>
	</section>

	<section id="async.f.async_sleep">
	    <title>
		<function moreinfo="none">async_sleep(seconds)</function>
	    </title>
	    <para>
		Simulate a sleep of 'seconds' and then continue the processing of SIP
		request with the next action. In case of internal errors, the function
		returns false.
		</para>
		<para>
		The sleep parameter represent the number of seconds to suspend the
		processing of SIP request. Maximum value is 100. The parameter can be
		a static integer or a variable holding an integer.
		</para>
		<para>
		This function can be used from REQUEST_ROUTE.
		</para>
		<example>
		<title><function>async_sleep</function> usage</title>
		<programlisting format="linespecific">
...
async_sleep("4");
send_reply("404", "Not found");
exit;
...
</programlisting>
	    </example>
	</section>

	<section id="async.f.async_task_route">
	    <title>
		<function moreinfo="none">async_task_route(routename)</function>
	    </title>
	    <para>
		Continue the processing of the SIP request with the route[routename]
		in one of the processes from core asynchronous framework. The core
		parameter async_workers has to be set to enable asynchronous
		framework. The task is executed as soon as a process from asynchronous
		framework is idle, there is no wait time for the task like for
		async_route(...).
		</para>
		<para>
		To enable the core asynchronous framework, you need to set the
		<emphasis>async_workers</emphasis> core parameter in the configuration
		file. See the core cookbook for more information.
		<example>
		<title><function>async_workers</function> usage</title>
		<programlisting format="linespecific">
...
; Enable 8 worker processes used by async and other modules
async_workers=8
...
</programlisting>
	    </example>
		</para>
		<para>
		In case of internal errors, the function returns false, otherwise the
		function exits the execution of the script at that moment (return
		0 behaviour).
		</para>
		<para>
		The routename parameter can be a static string or a dynamic string
		value with config variables.
		</para>
		<para>
		Since the SIP request handling is resumed in another process,
		the config file execution state is practically lost. Therefore beware
		that the execution of config after resume will end once the
		route[routename] is finished.
		</para>
		<para>
		This function can be used from REQUEST_ROUTE.
		</para>
		<example>
		<title><function>async_task_route</function> usage</title>
		<programlisting format="linespecific">
...
async_task_route("RESUME");
...
route[RESUME] {
   t_relay();
   exit;
}
...
</programlisting>
	    </example>
	</section>
	</section>
</chapter>

