Resilience

Resilience is not just fault-tolerance, it's beyond fault-tolerance. A Reactive system should fully recover from failure; this is known as self-healing.

In simple words, Resilient = React to failure.

Resilience means a Reactive system should respond to users even in the event of failures, by recovering itself. This is possible by isolating the failure handling to a different component. In a Reactive system, all failures are converted into messages and then processed.

For instance, in Akka Toolkit, Akka Streams (one of the popular Reactive Streams implementations) uses the supervision technique to do this failure handling.

Refer to Chapter 4, Building Reactive Applications with Akka, to understand this Supervision technique.