Load balancing geographically distributed nodes with varnish - a good idea?

Thomas Prommer thomas at prommer.net
Fri Sep 16 10:53:54 CEST 2011

Thanks Artur,

Can you provide some more detail/a reference pointer how you would see this
being managed on a DNS level? We are currently not managing our our DNS
server or have plans to do so. Are there OOTB DNS solutions that consider
the health status of defined nodes and adapt DNS dispatching accordingly?

Coming back to my original question, would using Varnish to load-balance
geographically distributed nodes be necessarily always a bad idea or an
acceptable and effective practice in high load scenarios? Naturally we would
be willing to sacrifice the loss of optimized latency and SEO benefits
temporarily in benefit of resolving cpu & mem peak conditions on one
particular thoughts.

Appreciate your input /Thomas

On Thu, Sep 15, 2011 at 11:54 AM, Artur Bergman <sky at crucially.net> wrote:

> Not really a lightthpd or varnish issue. DNS is really you answer.
> Also, if you get hit hard in on location, sending it somewhere else and you
> no longer have latency advantage/
> On Sep 15, 2011, at 8:32 AM, Thomas Prommer wrote:
> Varnish Community,
> We are managing a cluster farm of 6 nodes that are geographically
> distributed across Europe (Amsterdam, London, Lisbon, Frankfurt, Zurich,
> Milan) delivering our internationalized application for the appropriate
> CCTLD for such nodes. All nodes have the same server image and application
> deployed. The server distribution is critical to ensure low latency in local
> markets as well as for SEO reasons.
> The application is a simple LAMP application (no centralized data) that is
> using Varnish and Lighttpd Fast CGI for optimal scaling. However, we still
> run into scaling issues were essentially one node gets hit hard with local
> traffic while all the other severs are pretty idle.
> Our question is if there is a common recommendation of load balancing a
> server cluster where the servers are geographically distributed and also if
> varnish or the lighttpd fastcgi server would be more appropriate to carry
> out the load balancing?
> We know that both systems allow for load balancing but we are concerned
> that simply load balancing the IPs of geographically servers wouldn't
> perform too well because an additional round trip to a remote server
> location would be introduced.
> In a nutshell, our questions are:
> Are there any good strategies around load balancing geographical
> distributed servers?
> What are the evaluation points for deciding if either Varnish or Lighttpd
> FastCGI would be more appropriate to own the load balancing responsibility?
> Thanks /Thomas
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