Database.CQRS.InMemory

Documentation

data Stream metadata event

In-memory event stream.

It's using STM internally so it's safe to have different thread writing events to the stream concurrently. Its main purpose is for tests but it could be used for production code as well.

Instances

(MonadError Error m, MonadIO m, NFData event, NFData metadata) => WritableStream m (Stream metadata event)

Defined in Database.CQRS.InMemory

Methods

writeEventWithMetadata :: Stream metadata event -> EventType (Stream metadata event) -> EventMetadata (Stream metadata event) -> ConsistencyCheck (EventIdentifier (Stream metadata event)) -> m (EventIdentifier (Stream metadata event))

MonadIO m => Stream m (Stream metadata event)

Defined in Database.CQRS.InMemory

Associated Types

type EventType (Stream metadata event) :: Type

type EventIdentifier (Stream metadata event) :: Type

type EventMetadata (Stream metadata event) :: Type

Methods

streamEvents :: Stream metadata event -> StreamBounds' (Stream metadata event) -> Producer [Either (EventIdentifier (Stream metadata event), String) (EventWithContext' (Stream metadata event))] m ()

type EventType (Stream metadata event)

Defined in Database.CQRS.InMemory

type EventType (Stream metadata event) = event

type EventIdentifier (Stream metadata event)

Defined in Database.CQRS.InMemory

type EventIdentifier (Stream metadata event) = Integer

type EventMetadata (Stream metadata event)

Defined in Database.CQRS.InMemory

type EventMetadata (Stream metadata event) = metadata

emptyStream :: MonadIO m => m (Stream metadata event)

Initialise an empty event stream.

data StreamFamily identifier metadata event

A family of in-memory streams.

There are two things to be aware of when using this type:

getStream adds a new empty stream to the family regardless of whether it's used or not. If an attacker can make your application call getStream with arbitrary stream identifiers, it can lead to a Denial-of-Service attack.

Slow consumers of event notifications (from allNewEvents) could become an issue if events are written at a higher pace that they can keep up with. In order to avoid the queue of notifications to grow bigger and bigger, it's capped at 100 (hard-coded for now.) This means that writing a new event can be blocked by a full consumer's queue.

Instances

(Eq identifier, Hashable identifier, MonadIO m) => StreamFamily m (StreamFamily identifier metadata event)

Defined in Database.CQRS.InMemory

Associated Types

type StreamType (StreamFamily identifier metadata event) :: Type

type StreamIdentifier (StreamFamily identifier metadata event) :: Type

Methods

getStream :: StreamFamily identifier metadata event -> StreamIdentifier (StreamFamily identifier metadata event) -> m (StreamType (StreamFamily identifier metadata event))

allNewEvents :: StreamFamily identifier metadata event -> m (Producer [(StreamIdentifier (StreamFamily identifier metadata event), Either (EventIdentifier (StreamType (StreamFamily identifier metadata event)), String) (EventWithContext' (StreamType (StreamFamily identifier metadata event))))] m a)

latestEventIdentifiers :: StreamFamily identifier metadata event -> Producer (StreamIdentifier (StreamFamily identifier metadata event), EventIdentifier (StreamType (StreamFamily identifier metadata event))) m ()

type StreamType (StreamFamily identifier metadata event)

Defined in Database.CQRS.InMemory

type StreamType (StreamFamily identifier metadata event) = Stream metadata event

type StreamIdentifier (StreamFamily identifier metadata event)

Defined in Database.CQRS.InMemory

type StreamIdentifier (StreamFamily identifier metadata event) = identifier

emptyStreamFamily :: forall metadata identifier event m. MonadIO m => m (StreamFamily identifier metadata event)

Initialise an empty stream family.