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

[Nathan Angelacos]

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...")