Moy Blog

I have been coding some new stuff for Asterisk lately, but the feature I like the most is Asynchronous AGI. I got the idea from MAGI, an old patch written by David Pollak that allowed AGI execution thru the manager interface. For those ignoring what AGI and AMI are, go read:

Asterisk Gateway Interface ( AGI )
Asterisk Manager API ( AMI )

So, my patch, allow users to execute AGI commands using “Action: AGI” and get the response reading “Event: AsyncAGI”. The manager header “CommandID” can be specified to match up the responses. Let’s see an example

In extensions.ael you would put something like this:

context sample-async-agi {
    test => {
        AGI(agi:async);
    };
};

That will put the channel to wait AGI commands. The channel will NOT do anything but wait for Hangup or any AGI command you ask it to execute. AGI commands can arrive from 2 sources. The most important and useful source of commands is the manager, but with my patch you can also execute AGI from the command line. Let’s see how it is done from the manager:

# telnet localhost 5038
Action: Login
Username: test
Secret: test

Action: AGI
Channel: SIP/33-blah
Command: EXEC Playback tt-monkeys
CommandID: MyCommandID


That would cause Asterisk to execute the “Playback” application on channel SIP/33-blah, which MUST be in AGI(agi:async) application. After executing the command you will be able to read an event with the AGI response url-encoded. If the channel is not in Async AGI, the command will not be executed and you will get an error response.

As I said, you can use the command line to execute Async AGI as well, just like this:

tcore*CLI> agi exec SIP/testing-09a5b960 “EXEC startmusiconhold”
tcore*CLI> agi exec SIP/testing-09a5b960 “EXEC stopmusiconhold”
tcore*CLI> agi exec SIP/testing-09a5b960 “EXEC Dial(Agent/23)”

That will start MOH, then stop it, and finally will dial to the Agent 23. This means you can implement a Queue without using native buggy Asterisk queues. You can receive calls and send them to Async AGI to put them on hold, then, when you detect availability of some of your Agents, Dial() to that agent.

If you want to learn more about this feature here is the mantis bug entry: http://bugs.digium.com/view.php?id=11282.

If you want the patch back-ported to 1.4, I have one here: http://www.moythreads.com/asterisk-1.4.15-async-agi.patch

In case you find this patch useful, please try it in trunk as well and provide feedback in mantis. Even when some people has found this patch useful, some of the top developers at asterisk-dev are hesitating in accepting it because similar results can be obtained thru the use of FastAGI, however, me and other people at asterisk-dev are trying to prove the patch also makes easier the implementation of some applications.

This is a hot discussion we got some weeks ago about it: http://lists.digium.com/pipermail/asterisk-dev/2007-December/031046.html

See you!