New subject: Failover with dialog dmq while dialog state 2

10 May 2024

Hi Henning,

thank you for your reply. I did a lot testings during the past days and I think I found a
solution that is working, although it's very dirty...

I found out it is possible to send a manual KDMQ-Message to all Proxy-Nodes including the
one that it sending die KDMQ-Message. So I create a dialog state 4 message on ACK and
indeed the Dialog on all Peers are Updated correctly to state 4. I also tried this for
state 3 on 200 OK, but this does not work. I haven't had a look into the code yet but
my experiments shows, that there is never is state 3 update via DMQ, so I think it's
not implemented.

Interestingly the TM-Timer still times out after 300 seconds but in normal circumstances
this doesn't bother, because either the failed Kamailio will not trigger this, because
the Software or the Server crashed, or it tries to send a CANCEL that is denied because we
are in dialog state 4.

The only thing is your really have to be careful about your hash tables. You have to
delete them at the correct point.

I really need to test a lot at this point, but till now, billing seems to be OK even on
failover scenarios.

This is why I really like Kamailio :)

BR, Björn

Am 09.05.24 um 20:57 schrieb Henning Westerholt:

Hello,

thanks for the detailed e-mail. As also indicated in the module documentation, the dialog
module DMQ replication will not replicate everything, its main use-case is for profile
data sharing.
https://kamailio.org/docs/modules/5.8.x/modules/dialog.html#dialog.p.enable…

In the past months there have been some other discussions on the users lists about similar
scenarios (I think related to billing/accounting) and dialog with DMQ, which might be
interesting for you in this regard.

If you find issues where the DMQ synchronisation is lacking some functionality in the
dialog module, you can create a feature request in our issue tracker. There is of course
no guarantee that this limitation is also timely addressed.

Regarding the INVITE and CANCEL scenario, this is usually not related to dialog but to the
tm module. As you also mentioned, there is no replication of transaction state in tm.

Cheers,

Henning

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Re: Failover with dialog dmq while dialog state 2