Gracefully stopping varnish

[Guillaume Quintard]

Hello,

So, there must be a misconception on my, because to me, just refusing new
connections isn't graceful. If the LB is sending you new connections, you
should honor them.

So, from what I get, k8s stops sending new connections to Varnish, and what
you want is is for Varnish to shutdown once there's no more active
connections, which is, I would argue, kinda different from refusing new
connections. But, let's stop being a pompous jerk obsessed with semantics
and let's try to work on a solution.

>From what I get, we can kill varnish as soon as the number of active
connections drops to 0, so your apachectl command would be equal to this in
Varnish language:

if [ `varnishstat -1 | awk '/MEMPOOL.sess[0-9]+.live/ {a+=$2} END {print
a}'` != 0 ]; then
    sleep 1
fi
killall varnishd


There's probably a shorter version ,but that's the gist of it.

Would that do?

-- 
Guillaume Quintard

On Wed, Oct 18, 2017 at 8:22 PM, Hugues Alary <hugues at betabrand.com> wrote:

> Hi,
>
> That is indeed what I want to do. Draining connections at the LB level
> just involves more work ;).
>
> For context: my entire stack runs on a kubernetes cluster.
>
> I sometime need to replace a running instance of a server process [be it
> nginx apache php-fpm varnish whatever] with a new instance.
>
> Taking Apache as an example, I simply create the new apache instance (a
> new pod in kubernetes speak), which immediately starts getting some traffic
> (without changing the load balancer configuration at all, a kubernetes
> "service" automatically detects new pods), then I gracefully shutdown the
> old instance (kubernetes actually automatically tells the pod to shutdown),
> by issuing a "apachectl -k graceful-stop" (kubernetes is configured to
> issue this command for me), which instructs apache to stop accepting
> connections, finish, then shutdown.
>
> It's really great because instead of having to push a new config refusing
> probes and reload it, I (/kubernetes) simply gracefully stops apache and
> the traffic flows to the new instance. nginx and php-fpm also handle things
> this way.
>
> At any rate, thanks for the advice, I will start using probes!
>
> Cheers,
> -Hugues
>
>
>
> On Tue, Oct 17, 2017 at 11:51 PM, Guillaume Quintard <
> guillaume at varnish-software.com> wrote:
>
>> Hi,
>>
>> That's not possible. However, what you really want, I think, is not
>> sending new requests to Varnish. That's usually done at the loa-bbalancing
>> level. If your LB use probes, you can tell Varnish to stop honoring them,
>> drain the connections,  then kill it.
>>
>> --
>> Guillaume Quintard
>>
>> On Oct 18, 2017 02:28, "Hugues Alary" <hugues at betabrand.com> wrote:
>>
>>> Hi there,
>>>
>>> I've been looking around and I can't find a documented way of gracefully
>>> shutting down varnishd, and by gracefully I mean tell varnish "stop
>>> accepting connections, but finish what you were doing, then shutdown".
>>>
>>> I did find something in the "first varnish design notes" (
>>> https://varnish-cache.org/docs/5.1/phk/firstdesign.html) which seemed
>>> to indicate that sending SIGKILL/SIGTERM would mean "suspend/stop" but KILL
>>> doesn't seem to work, and TERM, well... terminates but not gracefully.
>>>
>>> I also tried using "varnishadm stop", which also doesn't gracefully
>>> stops connection.
>>>
>>> Is there anyway to achieve this?
>>>
>>> Thanks!
>>> -Hugues
>>>
>>> _______________________________________________
>>> varnish-misc mailing list
>>> varnish-misc at varnish-cache.org
>>> https://www.varnish-cache.org/lists/mailman/listinfo/varnish-misc
>>>
>>
>
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