[OpenSIPS-Users] Asynchronous processing in OpenSIPS 1.12

[Răzvan Crainea]

Hi all,

Among the last discussion of the last IRC meeting[1] was related to 
Asynchronous processing in OpenSIPS script - we want to add a new 
mechanism that allows you to perform asynchronous operations (such as DB 
, REST or exec operations) directly from the script. Using this feature 
will increase the throughput of OpenSIPS, since the SIP processes will 
no longer be stuck waiting for I/O responses.

When reaching an asynchronous operation, the SIP message processing will 
be stopped, and resumed in a different script route. In the script, this 
should be reflected something like this:

route {
     ...
     # other non I/O operations
     async(my_resume_route) {
         avp_db_query("SELECT setid from subscribers where username = 
'$fU'", "$avp(setid)");
     }
     # we never get here.
     exit;
}

route[my_resume_route] {
     xlog("The set used by the callee is $avp(setid)\n");
     # continue message processing
}

Only the functions that are used in an "async" block will be ran 
asynchronously. If the function does not support async processing, it 
will block waiting for the response and resume in the route indicated by 
the "async" block - so the scripting experience will be the same even if 
the async OP could not be done.
In order to resume the processing in a different route, we need to store 
a context of the message. This will be done using the transaction 
module[2]. If this module is not used, the asynchronous mechanism will 
not work.

lirakis suggested to have different processes that waits for the 
asynchronous I/O responses and continues the processing. However, we 
think having the SIP worker processes resume the operations will behave 
better, since we'll have fewer processes and we won't loose time with 
context switches.

How do you see this feature? How would you like to use it? Feel free to 
contribute with any input you find suitable!

[1] http://www.opensips.org/Community/IRCmeeting20140827
[2] http://www.opensips.org/html/docs/modules/1.12.x/tm

Best regards,

-- 
Răzvan Crainea
OpenSIPS Solutions
www.opensips-solutions.com