We usually already have a high enough number of max tcp connections. However, there are certain scenarios when restarting some of our servers the loadbalancer sends all the clients previously connected to these servers to the remaining ones, leading to really
full and really empty nodes. And sometimes we see Kamailio rejecting connections, and sometimes maybe the client can still connect, but the outgoing connection to the next hop is not possible anymore.
But maybe you're right. Manually dropping the connection would probably not be any better than what Kamailio does after really reaching the limit.
We have already implemented the maintenance mode draining, this would work as follows:
Add a shared var named "MAINTENANCE_MODE", set it to 0 in config. Then, when handling the REGISTER, add something like this:
if msg.is_method("REGISTER"):
if KSR.pv.get("$shv(MAINTENANCE_MODE)") == 1:
msg.log("In maintenance mode, rejecting registration")
KSR.set_reply_close()
KSR.hdr.append_to_reply("Retry-After: 3\r\n")
KSR.sl.sl_send_reply(503, "Draining")
return False
You can set the value of the shared var to 1 via kamcmd. After that, on the next re-registration,
the client will be disconnected, ending up hopefully on a different node after reconnect.
Regards,
Sebastian
Why not just increase the max tcp connections? Also, once you hit it, Kamailio will
reset the syn and the load balancer should try on a different server.
I am look for something like what you’re looking for but reset the sub on-demand so
I can put the server in maintenance mode.
Regards,
David Villasmil
phone: +34669448337
Hello,
My plan is to reject new inbound requests if there is already a certain number of open connections on one Kamailio
server. I could answer with a 503 and directly close the connection forcing the client to reconnect and the loadbalancer to send traffic to a different node on the next connect. It's just a last-resort measure to prevent Kamailio from running into the configured
TCP connection limit (workarounding a poorly-implemented external load balancer).
Since I didn't find anything in the docs: Is there a pseudovariable containing the current number of open tcp/tls
connections on this Kamailio? I can (and already do) query them via kamcmd or rpc, but can I access the variable from inside the routing script as well?
Regards,
Sebastian
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