Distributed Queue Example

Programs can use distributed queues for one-of-n certified delivery to a group of servers, in order to balance the load among the servers.

This example illustrates a distributed group of database servers that accept certified messages representing tasks (updates and queries). Rendezvous distributed queue software assigns each task to exactly one of the servers, while the group of servers and the distribution of tasks remains completely transparent to the client processes.

Figure 18 illustrates a server group as a cloud of distributed queue members. From outside, the group appears to be a single transport object; inside the cloud, the members act in concert to process inbound task messages. A program outside the group sends a task message to the group; notice that the sender is not a group member, and does not do anything special to send its message to a group; rather, it sends its message to an ordinary subject name. Inside the group, the member acting as scheduler assigns each task message to exactly one of the workers; only that worker processes the task message.

Figure 18 One-of-N Delivery to a Distributed Queue