[OpenSIPS-Users] Asynchronous processing in OpenSIPS 1.12

[Bogdan-Andrei Iancu]

On 03.09.2014 13:02, Saúl Ibarra Corretgé wrote:
> On 03 Sep 2014, at 11:59, Bogdan-Andrei Iancu <bogdan at opensips.org> wrote:
>
>> On 03.09.2014 12:06, Saúl Ibarra Corretgé wrote:
>>> On 02 Sep 2014, at 18:26, Răzvan Crainea <razvan at opensips.org> wrote:
>>>
>>>> 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.
>>> I find this quite problematic. How does John Doe know a function supports async or not? Maybe the configuration checker can know this and not let OpenSIPS start if you are doing it wrong? Alternatively, blocking functions could be ran in a thread pool thus giving the illusion of them being async.
>> First of all, the function will be documented as supporting Async and the script parser may check it (we will export some extra flags for the function to say "it can do async").
>>
>> Secondly, the script will allow you to use any combination of functions and script macro - I mean the script will allow you to use an async function in a non-async way (and the function will act as sync) or to use a non-async function in an async way (the function will act as async and with a jump to resume route).
>>
> My concern is with that last part: if a function which doesn’t support async is called within an async block it will block but then make the jump thus deceiving the user into believing it was async when it isn’t. We need to fail loudly and tell users they are doing it wrong, iMHO.
Of course, we can detect that at script parsing and decide how to handle it:
     - ignore and do it blocking
     - warning and do it blocking
     - error and do not start.

Regards,
Bogdan