Caching OSM tiles - how to not overload backends?

[Damien Wetzel]

Hi Tranxène50
I'm a reseller of Fastly in France a cdn based on a fork of varnish 2
maybe it could be a solution to minimize the backend traffic you receive somehow ?
i can make you test if needed
akamai has a solution they call waiting room, to regulate the traffic to the origin,
i think this is the kind of things to try to achieve ?
Best Regards,
Damien 

tranxene50 writes:
 > 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 <dridi at varni.sh> 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
 >         <tranxene50 at openvz-diff-backups.fr> 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";
 >         >   .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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