[SR-Users] What happens to calls when Kamailio restarts?

[Alex Balashov]

That said, while there are doubtless some environments so large that
this becomes a significant business question, I would think carefully
about whether this problem is truly worth solving before designing any
overly Rube-Goldbergian coping mechanism.

So, CANCELs for a small amount of calls in flight don't make it out the
door. Big deal? The two endpoints will sooner rather than later, by
various kinds of dead peer detection, discover that the other end is
dead. If you restart during a quiet / low-volume time, you can probably
keep this sort of thing to a minimum. 

If it truly counts, by all means do it, but in my experience there are a
lot of folks with "high volume" ideas that are more fantasy than reality
who spend a lot of capital designing and optimising for availability
scenarios that never turn out to be a problem. I don't know how many
times I have heard in Kamailio consulting work that this registrar needs
to support five million endpoints and never be down and ... well, that
bridge is just never remotely crossed. Off by a few orders of
magnitude. :-)

-- Alex

On Thu, Jul 13, 2017 at 06:22:55PM +0000, Samuel F. wrote:

> Thank you for the responses! As a follow up question, how do companies with large loads on their Kamailios handle restarts especially considering the CANCELs?
> 
> What is a good (business) process to restart a Kamailio without incurring any interruptions at all? What other components in the infrastructure would be in place and which ones are in use in the wild?
> 
> 
> // Samuel
> 
> ________________________________
> From: sr-users <sr-users-bounces at lists.kamailio.org> on behalf of Sebastian Damm <damm at sipgate.de>
> Sent: Thursday, July 13, 2017 2:39:39 PM
> To: Kamailio (SER) - Users Mailing List
> Subject: Re: [SR-Users] What happens to calls when Kamailio restarts?
> 
> Hi,
> 
> On Wed, Jul 12, 2017 at 11:53 AM, Alex Balashov
> <abalashov at evaristesys.com> wrote:
> > All SIP messages passing through the proxy can be forwarded statelessly
> > and based on properties of the SIP message alone.
> 
> There's one thing that could happen: Calls that get cancelled after a
> restart, could possibly keep on ringing on the far end. At least if
> you check for an active transaction in your kamailio config.
> 
>   if (!t_check_trans()) {
>       sl_send_reply("481", "Call/Transaction does not exist");
>       xlog("L_ERR", "CANCEL: found no matching transaction F=$fu T=$tu
> R=$ru\n");
>       return;
>   }
> 
> And if you do some sort of random dispatching, CANCELs could end up on
> a different gateway.
> 
> But other than that, a restart shouldn't cause much trouble.
> Especially in-call requests get routed by Route headers only.
> 
> Regards,
> Sebastian
> 
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-- 
Alex Balashov | Principal | Evariste Systems LLC

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