Command Handler

The Command Handler has the responsibility of running the commands which means doing the following steps:

• get the state/s of the aggregate/s invoved on the command.
• try to run commands on that states,
• try to store the resulting events,
• send the events to the event broker,
• making periodic snapshots, according to the SnapshotsInterval. Those steps are enveloped by a result computation expression expressing explicitly the "happy path" and implicitly the "error path" using monading operators. Note: The only real success occurs after the event store is stored. The delivery of the messages does not affect the result of running the command. Any message listener can implement a "fallback" policy so thy they can be rehydrated by a call to the event store to restore the correct state of the aggregate.

CommandHandler.fs