Hello,

 

regarding limiting the number of gateways retries, you can use different failure routes (e.g. jump from first to second and then stop), you can keep an counter, or probably just rely on ds_next_dst() reaching the end of available gateways in the XAVP (did not checked code).

 

Cheers,

 

Henning

 

--

Henning Westerholt – https://skalatan.de/blog/

Kamailio services – https://gilawa.com

 

From: Unai Rodriguez <unai@rodr.org>
Sent: Tuesday, December 13, 2022 5:32 PM
To: Kamailio (SER) - Users Mailing List <sr-users@lists.kamailio.org>; Henning Westerholt <hw@gilawa.com>
Subject: RE: [SR-Users] How to have Kamailio retry backends

 

Hi Henning/All,

After some digging we realized the system was already retrying thanks to this block on kamailio.cfg

# Try next destionations in failure route
failure_route[RTF_DISPATCH] {
    if (t_is_canceled()) {
        exit;
    }
    # next DST - only for 500 or local timeout
    if (t_check_status("500")
            or (t_branch_timeout() and !t_branch_replied())) {
        if(ds_next_dst()) {
            t_on_failure("RTF_DISPATCH");
            route(RELAY);
            exit;
        }
    }
}

How can we control the maximum number of retries? Seems to be infinite at the moment? Or !t_branch_replied()means that each backend can only reply once?

Thanks you

 

With best wishes,

Unai Rodriguez

On 6 Dec 2022, 10:04 +0100, Henning Westerholt <hw@gilawa.com>, wrote:

Hello,

 

you can implement this by using a failure_route. There is one example in the dispatcher module configuration how to do it.

 

Cheers,

 

Henning

 

--

Henning Westerholt – https://skalatan.de/blog/

Kamailio services – https://gilawa.com

 

From: sr-users <sr-users-bounces@lists.kamailio.org> On Behalf Of Unai Rodriguez
Sent: Saturday, December 3, 2022 5:16 PM
To: sr-users@lists.kamailio.org
Subject: [SR-Users] How to have Kamailio retry backends

 

Dear List,

We’re using Kamailio to load balance MRCP requests to multiple backend groups with a configuration as follows:

# kamailio.cfg
...
...
route[DISPATCH] {
                if($ua=="mrcp_backend_1") {
                                if(!ds_select_dst("1", "4")) {
                                               send_reply("404", "No destination");
                                               exit;
                                }
                }
                if($ua=="mrcp_backend_2") {
                                if(!ds_select_dst("2", "4")) {
                                               send_reply("404", "No destination");
                                               exit;
                                }
                }
                xlog("L_DBG", "--- SCRIPT: going to <$ru> via <$du>\n");
                t_on_failure("RTF_DISPATCH");
                route(RELAY);
                exit;
}
...
...

# dispatcher.list
1 sip:mrcp01.server.int:8060;transport=tcp
1 sip:mrcp02.server.int:8060;transport=tcp

2 sip:mrcp03.server.int:8060;transport=tcp
2 sip:mrcp04.server.int:8060;transport=tcp

With this configuration, Kamailio load balances the initial SIP INVITE among the MRCP servers. After the INVITE, the service communicates directly to the MRCP servers via SIP (for hanging up the call), MRCPv2 (for sending speech control messages), and RTP (for sending audio).

We would like to implement a configurable number of retries, so that if a particular backend times out, Kamailio would retry X times to other backend(s). In short, something equivalent to HAProxy’s retries, but for Kamailio. This probably implies having Kamailio always as part of our communication (not just load balancing the initial SIP INVITE).

I haven’t been able to find much information about this, could someone provide some pointers?

Thank you so much

 

With best wishes,

Unai Rodriguez