Articles

Begining to think about Load Balancing

In Uncategorized on March 17, 2010 by petrem66 Tagged:

The complexity of building a web application from scratch is significant, even without having to worry about its availability, and fault tolerance. But such concerns are very important to acknowledge. One of them that I’ve just got to taste is the deployment.
With SSL enabled and fault tolerant applications one needs to imagine a load balancing capability that can not only dispatch requests well but also put less burden for request encryption/decryption on the web server. I’ve got the point that using an intermediate layer of SSL caching server layer would be needed in order to take on the processing demand related to SSL, allowing the CPU power to be 100% dedicated to processing the dynamic content for the web server application. In such a context, it would be nice to have one packet level Load Balancing Node (or Layer 4 LB) to dispatch to the SSL cashes, and another Load Balancer at the protocol level (or Layer 7 LB) to dispatch the HTTP request to the Web servers.
Also a good point is that the databases must be load balanced and replicated transparently from the application. For Postgresql, that is my db of choice, there is very nice open source package for that called Sequoia distributed under the Apache License 2 (remember that this is a permissive Lesser license agreement) . Of course people at Continuent have abandoned Sequoia since 2008, and now offer Tungsten (Replicator, Load Balancer …) for a fee or under GNU licensing model.
It seem that Rackspace promotes a simple Load Balancer with Apache. I think that’s good enough for testing

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