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

[Ramesh T S]

powerdns with geoip should be good starters + ruby module for service health checks.

From: Thomas Prommer <thomas at prommer.net>
Sent: Fri, 16 Sep 2011 14:26:09 
To: Artur Bergman <sky at crucially.net>
Cc: varnish-dev at varnish-cache.org
Subject: Re: Load balancing geographically distributed nodes with varnish - a good idea?
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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