1.3.9 Instance Load Balancing

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COMA also supports instance load balancing, in which instantiation of components is automatically distributed across instance containers on multiple servers, according to run-time information, such as the comparative load on each server. Instance container load balancing also enables a rudimentary form of failover, in which a server that is experiencing system failures is temporarily disabled so that it can be restarted or otherwise returned to a good state.

An ORB that performs instance load balancing is said to be configured as an instance load balancing router. A machine that participates in instance load balancing as a target for component instantiation is known as an instance load balancing target. COMA enables configuration of instance container load balancing as follows:

  • A COMA server optionally enables instance load balancing support to be started or stopped for its configured ORB.

  • The machine settings object has a configuration property that indicates whether the target ORB is configured as an instance load balancing router and, optionally, enables a client to change this configuration.

  • A COMA server that configures an instance load balancing router, exposes its list of instance load balancing targets in its catalog, and allows this list to be modified.