Mailing List Archive

Usage of the Shard director ( rampup period )
Hello all,
I'm trying to use the Shard director

sub vcl_init {
new dir_b = directors.shard();
dir_b .add_backend(wb3);
dir_b .add_backend(wb2);
dir_b.add_backend(wb1);
dir_b .set_rampup(2m);
dir_b .reconfigure();
}

I'm trying to debug rampup period for a failed backend, cause it seems to
me that the server is getting back in the pool before the 2 minutes rampup
period.

Any ideas will be appreciated.

Regards
Re: Usage of the Shard director ( rampup period ) [ In reply to ]
Hi,

Did you configure probes for that backend?

--
Guillaume Quintard


On Thu, Nov 14, 2019 at 2:45 AM Yiannis Karayiannidis <
y.karayiannidis@stoiximan.gr> wrote:

> Hello all,
> I'm trying to use the Shard director
>
> sub vcl_init {
> new dir_b = directors.shard();
> dir_b .add_backend(wb3);
> dir_b .add_backend(wb2);
> dir_b.add_backend(wb1);
> dir_b .set_rampup(2m);
> dir_b .reconfigure();
> }
>
> I'm trying to debug rampup period for a failed backend, cause it seems to
> me that the server is getting back in the pool before the 2 minutes rampup
> period.
>
> Any ideas will be appreciated.
>
> Regards
>
> _______________________________________________
> varnish-misc mailing list
> varnish-misc@varnish-cache.org
> https://www.varnish-cache.org/lists/mailman/listinfo/varnish-misc
>
Re: Usage of the Shard director ( rampup period ) [ In reply to ]
On 11/14/19 11:43, Yiannis Karayiannidis wrote:
>
> sub vcl_init {
> new dir_b = directors.shard();
> dir_b .add_backend(wb3);
> dir_b .add_backend(wb2);
> dir_b.add_backend(wb1);
> dir_b .set_rampup(2m);
> dir_b .reconfigure();
> }
>
> I'm trying to debug rampup period for a failed backend, cause it seems to
> me that the server is getting back in the pool before the 2 minutes rampup
> period.

What exactly do you mean by "getting back in the pool before the 2
minutes"? What were you expecting?

Rampup means that requests are directed to a backend, gradually and
increasingly, during the rampup period after a backend is added to the
pool. Say after the backend goes from failing health probes to being
healthy again.

Specifically, set_rampup(2m) means that during the two minutes after a
backend is added to the pool, requests are directed to the alternative
backend with linear decreasing probability, from 100% just after the
backend is added, to 0% after the two minutes are up. For example, at 90
seconds, there is a 75% probability that the backend will receive
requests that sharding would direct to it.

So it's to be expected that a backend will receive requests during rampup.


HTH,
Geoff
--
** * * UPLEX - Nils Goroll Systemoptimierung

Scheffelstraße 32
22301 Hamburg

Tel +49 40 2880 5731
Mob +49 176 636 90917
Fax +49 40 42949753

http://uplex.de
Re: Usage of the Shard director ( rampup period ) [ In reply to ]
Hello Guys,
thanks a lot for the answer Geof.
The shard director does what is expected to do.
It was a misunderstanding from my side.

Thanks again
and sorry for the noise

Regards



On Thu, Nov 14, 2019 at 8:32 PM Geoff Simmons <geoff@uplex.de> wrote:

> On 11/14/19 11:43, Yiannis Karayiannidis wrote:
> >
> > sub vcl_init {
> > new dir_b = directors.shard();
> > dir_b .add_backend(wb3);
> > dir_b .add_backend(wb2);
> > dir_b.add_backend(wb1);
> > dir_b .set_rampup(2m);
> > dir_b .reconfigure();
> > }
> >
> > I'm trying to debug rampup period for a failed backend, cause it seems
> to
> > me that the server is getting back in the pool before the 2 minutes
> rampup
> > period.
>
> What exactly do you mean by "getting back in the pool before the 2
> minutes"? What were you expecting?
>
> Rampup means that requests are directed to a backend, gradually and
> increasingly, during the rampup period after a backend is added to the
> pool. Say after the backend goes from failing health probes to being
> healthy again.
>
> Specifically, set_rampup(2m) means that during the two minutes after a
> backend is added to the pool, requests are directed to the alternative
> backend with linear decreasing probability, from 100% just after the
> backend is added, to 0% after the two minutes are up. For example, at 90
> seconds, there is a 75% probability that the backend will receive
> requests that sharding would direct to it.
>
> So it's to be expected that a backend will receive requests during rampup.
>
>
> HTH,
> Geoff
> --
> ** * * UPLEX - Nils Goroll Systemoptimierung
>
> Scheffelstraße 32
> 22301 Hamburg
>
> Tel +49 40 2880 5731
> Mob +49 176 636 90917
> Fax +49 40 42949753
>
> http://uplex.de
>
> _______________________________________________
> varnish-misc mailing list
> varnish-misc@varnish-cache.org
> https://www.varnish-cache.org/lists/mailman/listinfo/varnish-misc
>


--

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Yiannis Karayiannidis
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