<a id="fault-tolerance-sample"></a>

Diagrams of the Fault Tolerance Sample

The above diagram illustrates the normal message flow.

Normal flow:

Step	Description
1	The progress Listener starts the work.
2	The Worker schedules work by sending Do messages periodically to itself
3, 4, 5	When receiving Do the Worker tells the CounterService to increment the counter, three times. The Increment message is forwarded to the Counter, which updates its counter variable and sends current value to the Storage.
6, 7	The Worker asks the CounterService of current value of the counter and pipes the result back to the Listener.

The above diagram illustrates what happens in case of storage failure.

Failure flow:

Step	Description
1	The Storage throws StorageException.
2	The CounterService is supervisor of the Storage and restarts the Storage when StorageException is thrown.
3, 4, 5, 6	The Storage continues to fail and is restarted.
7	After 3 failures and restarts within 5 seconds the Storage is stopped by its supervisor, i.e. the CounterService.
8	The CounterService is also watching the Storage for termination and receives the Terminated message when the Storage has been stopped ...
9, 10, 11	and tells the Counter that there is no Storage.
12	The CounterService schedules a Reconnect message to itself.
13, 14	When it receives the Reconnect message it creates a new Storage ...
15, 16	and tells the Counter to use the new Storage

Full Source Code of the Fault Tolerance Sample

Scala : @@snip FaultHandlingDocSample.scala { #all }

Java : @@snip FaultHandlingDocSample.java { #all }