Alex Le’s Blog

For the past few days I’ve been working on the cluster project again, after a month of suspension. Finally today I was able to configure a (almost) working load balancer with 3 web servers (1 is the loadbalancer itself, and 2 other dedicated web servers, web01 and web02). I’m in the process of writing down the scripts which I will follow later on to do the screencast. At this stage, what I have is half of the whole picture of a web cluster:

• Failover loadbalancer server pair, running Heartbeat and ldirectord
• A small cluster of 3 load-balanced web servers, using weighted round robin
• A pair of Nameserver to provide name-lookup service for the entire cluster, no more “ping 10.10.10.10.101.101.10.12“!

What is missing is the loadbalanced MySQL cluster. I have been able to get a cluster of 3 MySQL boxes working, but now I’d like to add the ipvsadm and ldirectord to provide load-balancing feature so that the cluster can be scaled up easier.

I am pretty proud of myself for learning all of these amazing technologies within a relatively short period of time. Especially for the DNS, I have learned so much about the networking aspect of a network of computer. The two books, “DNS & BIND” and “BIND Cookbook”, both by O’Reilly, are amazing reference source. I particularly like the “DNS & BIND” book for its in depth coverage on the concept of how nameservers work. Without that fundamental knowledge, it’s hard to build such a working cluster with growing demands.

Here is the revised virtual Linux cluster diagram. So slowly but surely my cluster project is reaching its destination: a complete virtualized web cluster running on VMWare. And once this is done, I think I begin to learn how to develop cluster-ready applications.