[SR-Users] Can this be done with xhttp module (3.1 devel)?

[Alex Balashov]

Sergey,

On 10/01/2010 06:11 PM, Sergey Okhapkin wrote:

> There is a way, t_uac_dlg MI does that. I wonder why something similar is not
> available from cfg script. You can issue http request and wait for response
> from cfg, it would be nice to have  t_uac_dlg() script function too.

You can send a request from script, sure.  That's what uac_req_send() 
does;  t_uac_dlg is just its MI equivalent, allowing that action to be 
externally stimulated.  Unless I am missing something that is not in 
the documentation, t_uac_dlg does not wait for a reply either.  Or 
does it?  I have not used it.

> I have no problem to run apache and invoke t_uac_dlg from CGI, but I'd prefer
> to avoid cgi overhead and implement kamailio-only based solution.

Understandably.  However, generally speaking, the architecture of 
Kamailio, and the entire *SER technology stack, is patterned after a 
strictly (external) event-driven process.  This means that route 
script is invoked only when messages are received;  some state 
information can be retained across sets of related messages 
(transactions, dialogs, etc.), but in principle, Kamailio does not sit 
around and block, waiting for replies to come back.

Given the present architecture, waiting on a response would be 
additionally problematic because Kamailio/sip-router does not use 
threads per se.  It spawns a set of forked processes which act as 
worker threads that are specialised into different roles, but these 
are finite in nature.  It would be catastrophic to throughput to have 
one of these pause and block, waiting on a reply before returning from 
an invocation of route script for a given message.

-- 
Alex Balashov - Principal
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