cqrs-types-0.9.0: Command-Query Responsibility Segregation. Modules for the basic types.

Safe HaskellNone



Event store backend. You only need to import this module if you're planning on implementing a custom event store backend.



class EventStoreBackend esb whereSource

Event stores are the backend used for reading and storing all the information about recorded events.


esbStoreEvents :: esb -> GUID -> Int -> [RawEvent] -> IO ()Source

Store a sequence of events for aggregate identified by GUID into the event store, starting at the provided version number. If the version number does not match the expected value, a failure occurs.

esbRetrieveEvents :: esb -> GUID -> Int -> Source (ResourceT IO) RawEventSource

Retrieve the sequence of events associated with the aggregate identified by the given GUID. Only events at or after the given version number are retrieved. The events are returned in increasing order of version number.

esbEnumerateAllEvents :: esb -> Source (ResourceT IO) RawEventSource

Enumerate all events. There is no guarantee on the ordering of events except that events for any specific aggregate root are returned in order of version number.

esbWriteSnapshot :: esb -> GUID -> RawSnapshot -> IO ()Source

Write snapshot for aggregate identified by GUID and the given version number. The version number is NOT checked for validity. If the event store does not support snapshots this function may do nothing.

esbGetLatestSnapshot :: esb -> GUID -> IO (Maybe RawSnapshot)Source

Get latest snapshot of an aggregate identified by GUID. Returns the version number of the snapshot in addition to the data. An event store which does not support snapshots is permitted to return Nothing in all cases.

esbWithTransaction :: forall a. esb -> IO a -> IO aSource

Run transaction against the event store. The transaction is expected to commit if the supplied IO action runs to completion (i.e. doesn't throw an exception) and to rollback otherwise.

type RawEvent = PersistedEvent ByteStringSource

Raw event type. The data associated with an event is not translated in any way.