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
________________________________
From: David Villasmil <[email protected]>
Sent: Tuesday, February 6, 2024 13:11
To: Kamailio (SER) - Users Mailing List <[email protected]>
Cc: Sebastian Damm <[email protected]>
Subject: Re: [SR-Users] Get the amount of open TCP connection from routing logic
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
email: [email protected]<mailto:[email protected]>
phone: +34669448337
On Tue, 6 Feb 2024 at 12:47, Sebastian Damm via sr-users
<[email protected]<mailto:[email protected]>> wrote:
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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