Assigning a new RTPEngine for a call for the sake of failover - sr-users

15 Apr 2023

Hello,

I am trying to implement RTPEngine failover, where if a selected RTPEngine node fails in
the middle of the call (and not responding NG requests), I want to select an alternative
node. However, when I call rtpengine_manage(), it does not seem to select an alternative
node in case of a failure. To address this, I have attempted to check if
$avp(RTP_INSTANCE) is null after calling rtpengine_manage(), and then use
rtpengine_delete() to forget the selected RTPEngine node for the specific call, with the
expectation that Kamailio would assign a new RTPEngine node for subsequent SIP message
retries. However, it appears that rtpengine_delete() does not have the desired effect in
this regard.

Here is an excerpt of my code for reference:
```
route[RTP] {
#!ifdef WITH_RTPENGINE
	if (has_body("application/sdp")) {
		if ($avp(x_source) == "INTERNAL") {
			rtpengine_manage("replace-session-connection replace-origin direction=internal
direction=external");
		}
		else if ($avp(x_source) == "EXTERNAL") {
			rtpengine_manage("replace-session-connection replace-origin direction=external
direction=internal");
		}

		if ($avp(RTP_INSTANCE) == $null) {
			rtpengine_delete();
			drop();
		}
	}
#!endif
}
```

Can you please advise on how I can achieve the desired failover behavior? Is there another
function similar to `rtpengine_reset_call` that can make Kamailio forget the RTPEngine
node for a specific call?

Thank you!