Hello!
Many thanks for your answers! :-)
@Dridi:
You are right, writing a specific VMOD would be the ideal solution but
unfortunately I am not qualified for the job. ^^
By the way, I would like to thank all the people who are working hard to
enhance and maintain Varnish.
This software is absolutely awesome!
@Xavier:
Before considering HAProxy, I searched if quick and dirty hacks were
possible with iptables to limit simultaneous connexions and tc to shape
the traffic.
But, after a quick reading of the documentation of HAProxy, it became
clear that - as you said - it is a reliable solution.
So, thanks the for the hint!
Have a great day!
Le 16/06/2020 à 00:17, Xavier Leune a écrit :
Hello,
@tranxene50 if implementing a vmod can be very challenging, using
haproxy can be a great solution here. Please refer to this blog post:
https://www.haproxy.com/fr/blog/four-examples-of-haproxy-rate-limiting/ (or
in french ;)
https://www.haproxy.com/fr/blog/four-examples-of-haproxy-rate-limiting/ ).
The very first step is about setting a maximum connections number and
a queuing. Using haproxy as your backend would require low engineering
and a minimum overage.
Regards,
Le lun. 15 juin 2020 à 20:02, Dridi Boukelmoune <[email protected]> a écrit :
Bonsoir,
Unfortunately we don't have any sort of queuing on the backend side,
so besides implementing your own backend transport from scratch in a
VMOD there is currently no solution.
Cordialement,
Dridi
On Sun, Jun 14, 2020 at 2:32 AM tranxene50
<[email protected]
<mailto:[email protected]>> wrote:
>
> Hello!
>
> Please forgive my bad English, I live in France.
>
> Summary: how to cache - with Varnish - Open Street Map PNG
images without overloading OSM tiles servers?
>
> The question seems related to Varnish backends and
".max_connections" parameter.
>
> A far as I know, if ".max_connections" is reached for a backend,
Varnish sends 503 http errors.
>
> I understand the logic but would it be possible to queue these
incoming requests and wait until the selected backend is really
available?
>
> backend a_tile {
> .host = "a.tile.openstreetmap.org
<http://a.tile.openstreetmap.org>";
> .port = "80";
> .max_connections = 2;
> }
>
> If Varnish have, let's say 100 incoming requests in 1 second,
how can I handle this "spike" without overloading the backend?
>
> All my google searches were "dead ends" so I think the question
is poorly formulated.
>
> Note 1 : using [random|round_robin] directors could be a
temporary solution
> Note 2 : libvmod-dynamic is great but does not limit backend
simultaneous connexions
>
> Many thanks for your help!
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