DISTRIBUTED COMPUTING - Standard implementation features

Standard implementation features

The standard implementation (using Message Streams) extends the basic features of a caucus to provide members with a way to:

Pause a caucus
Resume a caucus
Send join messages
Distinguish between several different message types

The pause and resume feature is useful when clients need to synchronize shared data. By sending a TStandardCaucusPauseMessage, a caucus member can suspend message delivery within the caucus, causing all messages to queue internally. Once the shared data is synchronized, the caucus member sends a TStandardCaucusResumeMessage to continue communications. The framework then sends all queued messages to the caucus members. For more about pause and resume, read "Pausing and resuming a caucus" on page 55.

The standard implementation also supports join messages--when a new member joins a caucus, all caucus members are automatically notified.

With the addition of three message types--pause, resume, and join--on top of the leave and data messages of the abstract interface, it makes sense to provide a way to distinguish between the different types. The standard implementation includes enumerated values that allow a caucus member to evaluate an incoming message to determine its type--see "Receiving messages from a caucus" on page 53 for a complete list.

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