[SR-Users] Understanding t_relay

[Ryan Brindley]

Hey Daniel,

Thanks for the reply and pointers on what I'm doing wrong. I'll look into
the branch_failure_route and read the docs again to make sure I do serial
forking and not accidentally creating a parallel fork.

Does there happen to be any good resources (blog posts, wiki articles,
books, ancient Egyptian hieroglyphics) on better understanding the handling
of requests/responses in Kamailio? Or are the module docs the best
available resource?

Thanks,

Ryan

On Wed, Feb 4, 2015 at 1:02 PM, Daniel-Constantin Mierla <miconda at gmail.com>
wrote:

> 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
> Kamailio World Conference, May 27-29, 2015
> Berlin, Germany - http://www.kamailioworld.com
>
>
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