Creating a singleton actor across clusters
In some scenarios, it is required for you to have a singleton object within your whole cluster. The Akka Cluster Singleton module provides means to accomplish this task in an easy way.
This module picks the oldest node in the cluster to create your singleton actor. If this node gets removed from the cluster, then the module uses the same logic to decide where to deploy your singleton actor. First, it selects the oldest node in the cluster to recreate your singleton actor. Second, the module ensures that there is only one instance of your actor running within the whole cluster.
To demonstrate this behavior, we will make use of Auto Downing. This feature of Akka Cluster automatically marks a node Down and removes it from the cluster after a configurable amount of time. This feature is off by default.
Getting ready
For this recipe, we will set up a cluster of two nodes running on the same machine. For this, we will use two different ports specified in...