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