Each node hosts a Group Communication component, abstracted by:
Group communication components see each others and can dispatch messages, more accurately org.codehaus.wadi.group.Envelope, to each others.
WADI provides four implementations of the Group Communication API, defined in wadi-group:
Service Spaces are components building on top of the above group communication infrastructure. They provide a logical group communication service, which restricts the view that clients have of the cluster to the sub-set of the nodes hosting a given Service Space.
For instance, Service Space 1 is hosted by Node 1 and Node 3. Clients on Node 1 using the logical group communication service of Service Space 1 only see Node 3. Also, they can only dispatch messages to Node 3.
Service Spaces are used to share the physical group communication services of a node between multiple applications, e.g. Web-applications.