[SR-Users] Understanding t_relay

[Daniel-Constantin Mierla]

Hello,

On 04/02/15 16:28, Ryan Brindley wrote:
>
> Hey community,
>
> I'm trying to understand t_relay () when a forward times out.
>
> This is an abbreviated version of what i have:
>
> Request_route {
> ...
> Route(do1)
> }
>
> Route [do1]  {
> ...
> T_on_reply (1reply)
> T_on_failure (1fail)
> T_relay ()
> }
>
> Reply_route[1reply] {
> ...
> If (t_check_status (302)) {
>   Route (do2)
> }
> }
>
> Failure_route [1fail] {
> Xlog (dafail1)
> }
>
> Route [do2]{
> ...
> T_on_reply (2reply)
> T_on_failure (2fail)
> T_relay ()
> }
>
> Reply_route [2reply]{
> Xlog (twerked)
> }
>
> Failure_route [2fail]{
> Xlog (failured)
> }
>
> The case im currently interested in is when the first relay (do1)
> returns a 302 and then the second (do2) times out.
>
> What happens on the second when it times out, it hits the 1fail
> failure_route. This messes with my logic as i would've expected (and
> want to find out how to make it) hit the 2nd failure_route.
>
> I also noticed that if i loop and try the do2 again after the first
> failure it will then hit the 2fail route.
>
> Any clarification on this subject would be greatly appreciated,
>
It is not easy to follow your pseduo-code, but it is important to know
that the SIP response is handled in an onreply_route. Given that, you
cannot call t_relay() on a SIP response (reply). SIP responses are
routed automatically based on Via header.

t_relay() must be used only for SIP requests. If you sent the SIP
request to many destinations (parallel fork), the tm is waiting for all
branches to complete before executing failure_route, the selected
response is based on an algorithm derived from SIP RFC specs. If you
want to have a routing block executed on a negative reply, use
branch_failure_route - in it, you get the request for processing and you
can relay it again.

Cheers,
Daniel

-- 
Daniel-Constantin Mierla
http://twitter.com/#!/miconda - http://www.linkedin.com/in/miconda
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