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Programming Distributed Systems with YAMI4

9.3 Publish-Subscribe

The publish-subscribe example is a simple system where information flows from a single producer to zero or more consumers. This example represents an interesting family of distributed systems that have well-defined data sources and are based on reporting, measurements or filtering.

In this example the publisher is a regular server that establishes a listener on the given target and that exposes one object which can handle subscriptions from clients. The client program can be started in many instances, which shows that the management of subscriptions is well encapsulated so that the publisher can focus only on producing its data.

The easiest way to try this example is to perform the following actions:

Run the publisher part in its own console. Provide a single parameter that is a server target for listener - the shortest form of the target is tcp://*:*. The publisher will print its resolved target on the screen. After that the publisher will print a random value every second - this random value is published to whoever might be subscribed at any given moment.
Run one or more subscribers in other consoles, on the same or different machines in the network. Start it with the target address of the publisher. The subscriber should print the values that are produced by the publisher.