iSCALE - A Message Oriented Middleware (MOM)
The iSCALE component provides a Java Message Service (JMS) framework for inter-process communication. Processes communicate through a broker, which is responsible for routing and buffering messages. Multiple brokers can communicate with each other in order to traverse firewalls and for load balancing.
The Sentinel processes use a publisher/subscriber mechanism to communicate with each other. This allows a process to publish a message to a topic channel that multiple subscribers consume, without the publishing process knowing which process subscribes to it. Subscribers can receive published messages from publishers without knowing what publishers are available. This minimizes configuration and increases system stability and scalability. For example, when a new Wizard is added to the system, no configuration is required on the Sentinel side.
The publisher process publishes messages to topics (channel), and the subscriber processes subscribe to topics. The message broker then routes messages from publishers to subscribers based on topics they have registered.