Managing Clusters with Enterprise Manager and Packaging Applications in ColdFusion MX 7

Configuring Load Balancing

Of the two HA methods, load balancing is simpler to implement and configure. You use it to distribute requests across a number of computers, based on an algorithm for determining load. You can distribute requests with a simple method, such as a round-robin configuration (which isn’t technically load balanced), which sends requests to each computer in a sequence. Or, you could use a more complex distribution method based on CPU utilization. If you distribute load based on CPU utilization, you must use some sort of method to report the CPU load back to the load-balancing software. You can configure JRun clustering features to act as a simple load balancer, handing requests to the cluster members. There are three algorithms you can use to distribute load: round robin, weighted round robin and random round robin. Strictly speaking, these are not load balanced options. However you can use weighted round robin (WRR) to simulate a more complex load-balance configuration. By using WRR, you apply a weight to each machine in the cluster so that in a mixed-hardware environment where some machines may be more powerful than others, JRun sends a proportional request volume to more robust machines. Random round robin (RRR) distributes requests machines in the cluster randomly. As I mentioned earlier, round robin (RR) distributes requests sequentially to cluster participants.

Figure 3. Configuring a cluster with weighted round robin request distribution

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