Mastering Functional Programming

Fault-tolerance and supervision

Akka is built with resilience and fault-tolerance in mind. This means that if an actor fails as a result of an exception, there is a well-defined way it will automatically restart and restore its state. Akka organizes actors in hierarchies, and parent actors are responsible for the performance of their children. So, if a child fails, its parent is supposed to be responsible for restarting it. The idea is that the external world should not be affected by the problems of an actor's subordinates. If the problem happens, it is the supervisor's responsibility to solve it rather than escalating it further. And when the child actor restarts, it should be able to restore itself to the state it was at when it failed. ...