Clustering is available in WildFly out of the box. There is no all-in-one library that deals
with clustering, but rather a set of libraries that cover different kinds of aspects.
The following diagram shows the basic clustering architecture adopted by WildFly:
The backbone of JBoss clustering is the JGroups library, which provides communication
between members of the cluster using a multicast transmission.
Multicast is a protocol where data is transmitted simultaneously to a group of hosts that
have joined the appropriate multicast group. You can think about multicast as a radio or
television streaming where only those tuned to a particular frequency receive the stream-
The next building block is Infinispan , which handles the consistency of your application
across the cluster by means of a replicated and transactional JSR-107-compatible cache.
JSR-107 specifies the API and semantics for temporary in-memory caching of Java ob-
jects, including object creation, shared access, spooling, invalidation, and consistency
Before diving into some cluster examples, we will first need to describe how to set up a
cluster of WildFly nodes using the two available nodes: standalone cluster and domain
cluster . If you don't remember the difference between the standalone and domain mode or
what core domain elements are, you can revise the material from Chapter 2 , Your First
Java EE Application on WildFly .
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