[Kamailio-Users] Question regarding TM module DNS failover with SRV records

[Nathan Angelacos]

Daniel-Constantin Mierla wrote:
> 
> 
> On 12/10/09 5:49 PM, Nathan Angelacos wrote:
>> Daniel-Constantin Mierla wrote:
>>> Hello,
>>>
>>> On 12/10/09 5:29 AM, Nathan Angelacos wrote:
>>>>
>>>> According to the 1.5.x TM module documentation,
>>>> DNS failover is triggered by a 503 reply or a timeout.
>>>>
>>>> When using SRV records, it appears a 503 triggers the failure_route 
>>>> instead.
>>>>
>>>> Given:
>>>>
>>>> host -t srv _sip._udp.voip.example.net
>>>>  _sip._udp.voip.example.net has SRV record 1 0 5060 
>>>> fast-server.example.net.
>>>>  _sip._udp.voip.example.net has SRV record 2 0 5060 
>>>> slow-server.example.net.
>>>>
>>>> On an invite to voip.example.net, if fast-server does not respond 
>>>> within "fr_timer" seconds, t_relay fires off a serial branch 
>>>> (t_on_branch is triggered) and the invite goes to slow-server.
>>>>
>>>> If fast-server responds with a 503, the t_on_failure route is 
>>>> triggered instead, and the invite is not sent on to slow-server.
>>>>
>>>> If its not a bug in the module, does anyone have  clues of how to 
>>>> coax the next DNS SRV record out of the t_on_failure route?  Or what 
>>>> can be done to get t_relay to consume the 503?
>>>>
>>> does the 503 reply include a retry-after header?
>>
>> It did not.  Adding one generates the expected results.  Thanks!
>>
>> (Now to convince the customer to add the header - "It worked before 
>> with the other provider...")
>>
> then maybe is easier to patch kamailio 1.5. Look in modules/tm/t_reply.c
> 
> At line 708, replace:
> 
>             /* is the Retry-After header present (if present,
>              * it should be already parsed) */
>             hdr = t->uac[picked_branch].reply->headers;
>             for( ; hdr ; hdr=hdr->next)
>                 if (hdr->type==HDR_RETRY_AFTER_T)
>                     return 1;
>             return 0;
> 
> with:
> 
>          return 1;
> 
>

Thanks!

I'm still a newbie... I really appreciate your patience and help.

Thanks for checking the 3.0 code as well. Good to know that we could try 
to wait for it as well.