Apache Karaf Cellar provides an API to implement the cluster component. The default cluster component implementation is powered by Hazelcast.
Hazelcast is a clustering and scalable data distribution solution. It provides features that exactly match the needs for the cluster component, especially the following:
A distributed storage implementation. This is where Apache Karaf Cellar will store the resources' status.
A distributed topic for publish/subscribe messaging. Apache Karaf Cellar will use this distributed topic to implement cluster events.
These are the two functionalities we are looking for in our cluster component.
However, Hazelcast also provides additional features. Thanks to Hazelcast, Apache Karaf Cellar supports different ways to discover the nodes of the cluster: static IP address definition, multicast, and whiteboard registration. The following diagram shows the modules provided by Karaf:
The first thing to do is install Cellar in the different Karaf...