Eventful.Store.Class

EventStore

newtype EventStoreReader key position m event

An EventStoreReader is a function to query a stream from an event store. It operates in some monad m and returns events of type event from a stream at key ordered by position.

Constructors

EventStoreReader

Fields

• getEvents :: QueryRange key position -> m [event]

Instances

Functor m => Functor (EventStoreReader key position m)

Methods

fmap :: (a -> b) -> EventStoreReader key position m a -> EventStoreReader key position m b

(<$) :: a -> EventStoreReader key position m b -> EventStoreReader key position m a

newtype EventStoreWriter m event

An EventStoreWriter is a function to write some events of type event to an event store in some monad m.

Constructors

EventStoreWriter

Fields

• storeEvents :: ExpectedVersion -> UUID -> [event] -> m (Maybe EventWriteError)

Instances

Contravariant (EventStoreWriter m)

Methods

contramap :: (a -> b) -> EventStoreWriter m b -> EventStoreWriter m a

(>$) :: b -> EventStoreWriter m b -> EventStoreWriter m a

type VersionedEventStoreReader m event = EventStoreReader UUID EventVersion m (VersionedStreamEvent event)

type GlobalEventStoreReader m event = EventStoreReader () SequenceNumber m (GlobalStreamEvent event)

data StreamEvent key position event

An event along with the key for the event stream it is from and its position in that event stream.

Constructors

StreamEvent

Fields

• streamEventKey :: !key
• streamEventPosition :: !position
• streamEventEvent :: !event

Instances

Functor (StreamEvent key position)

Methods

fmap :: (a -> b) -> StreamEvent key position a -> StreamEvent key position b

(<$) :: a -> StreamEvent key position b -> StreamEvent key position a

Foldable (StreamEvent key position)

Methods

fold :: Monoid m => StreamEvent key position m -> m

foldMap :: Monoid m => (a -> m) -> StreamEvent key position a -> m

foldr :: (a -> b -> b) -> b -> StreamEvent key position a -> b

foldr' :: (a -> b -> b) -> b -> StreamEvent key position a -> b

foldl :: (b -> a -> b) -> b -> StreamEvent key position a -> b

foldl' :: (b -> a -> b) -> b -> StreamEvent key position a -> b

foldr1 :: (a -> a -> a) -> StreamEvent key position a -> a

foldl1 :: (a -> a -> a) -> StreamEvent key position a -> a

toList :: StreamEvent key position a -> [a]

null :: StreamEvent key position a -> Bool

length :: StreamEvent key position a -> Int

elem :: Eq a => a -> StreamEvent key position a -> Bool

maximum :: Ord a => StreamEvent key position a -> a

minimum :: Ord a => StreamEvent key position a -> a

sum :: Num a => StreamEvent key position a -> a

product :: Num a => StreamEvent key position a -> a

Traversable (StreamEvent key position)

Methods

traverse :: Applicative f => (a -> f b) -> StreamEvent key position a -> f (StreamEvent key position b)

sequenceA :: Applicative f => StreamEvent key position (f a) -> f (StreamEvent key position a)

mapM :: Monad m => (a -> m b) -> StreamEvent key position a -> m (StreamEvent key position b)

sequence :: Monad m => StreamEvent key position (m a) -> m (StreamEvent key position a)

(Eq event, Eq position, Eq key) => Eq (StreamEvent key position event)

Methods

(==) :: StreamEvent key position event -> StreamEvent key position event -> Bool

(/=) :: StreamEvent key position event -> StreamEvent key position event -> Bool

(Show event, Show position, Show key) => Show (StreamEvent key position event)

Methods

showsPrec :: Int -> StreamEvent key position event -> ShowS

show :: StreamEvent key position event -> String

showList :: [StreamEvent key position event] -> ShowS

type VersionedStreamEvent event = StreamEvent UUID EventVersion event

type GlobalStreamEvent event = StreamEvent () SequenceNumber (VersionedStreamEvent event)

data ExpectedVersion

ExpectedVersion is used to assert the event stream is at a certain version number. This is used when multiple writers are concurrently writing to the event store. If the expected version is incorrect, then storing fails.

Constructors

AnyVersion

Used when the writer doesn't care what version the stream is at.

NoStream

The stream shouldn't exist yet.

StreamExists

The stream should already exist.

ExactVersion EventVersion

Used to assert the stream is at a particular version.

Instances

Eq ExpectedVersion

Methods

(==) :: ExpectedVersion -> ExpectedVersion -> Bool

(/=) :: ExpectedVersion -> ExpectedVersion -> Bool

Show ExpectedVersion

Methods

showsPrec :: Int -> ExpectedVersion -> ShowS

show :: ExpectedVersion -> String

showList :: [ExpectedVersion] -> ShowS

data EventWriteError

Constructors

EventStreamNotAtExpectedVersion EventVersion

Instances

Eq EventWriteError

Methods

(==) :: EventWriteError -> EventWriteError -> Bool

(/=) :: EventWriteError -> EventWriteError -> Bool

Show EventWriteError

Methods

showsPrec :: Int -> EventWriteError -> ShowS

show :: EventWriteError -> String

showList :: [EventWriteError] -> ShowS

runEventStoreReaderUsing :: (Monad m, Monad mstore) => (forall a. mstore a -> m a) -> EventStoreReader key position mstore event -> EventStoreReader key position m event

Changes the monad an EventStoreReader runs in. This is useful to run event stores in another Monad while forgetting the original Monad.

runEventStoreWriterUsing :: (Monad m, Monad mstore) => (forall a. mstore a -> m a) -> EventStoreWriter mstore event -> EventStoreWriter m event

Analog of runEventStoreReaderUsing for a EventStoreWriter.

module Eventful.Store.Queries

Serialization

serializedEventStoreReader :: Monad m => Serializer event serialized -> EventStoreReader key position m serialized -> EventStoreReader key position m event

Wraps an EventStoreReader and transparently serializes/deserializes events for you. Note that in this implementation deserialization errors are simply ignored (the event is not returned).

serializedVersionedEventStoreReader :: Monad m => Serializer event serialized -> VersionedEventStoreReader m serialized -> VersionedEventStoreReader m event

Convenience wrapper around serializedEventStoreReader for VersionedEventStoreReader.

serializedGlobalEventStoreReader :: Monad m => Serializer event serialized -> GlobalEventStoreReader m serialized -> GlobalEventStoreReader m event

Convenience wrapper around serializedEventStoreReader for GlobalEventStoreReader.

serializedEventStoreWriter :: Monad m => Serializer event serialized -> EventStoreWriter m serialized -> EventStoreWriter m event

Like serializedEventStoreReader but for an EventStoreWriter. Note that EventStoreWriter is an instance of Contravariant, so you can just use contramap serialize instead of this function.

Utility types

newtype EventVersion

Event versions are a strictly increasing series of integers for each projection. They allow us to order the events when they are replayed, and they also help as a concurrency check in a multi-threaded environment so services modifying the projection can be sure the projection didn't change during their execution.

Constructors

EventVersion

Fields

• unEventVersion :: Int

Instances

Enum EventVersion

Methods

succ :: EventVersion -> EventVersion

pred :: EventVersion -> EventVersion

toEnum :: Int -> EventVersion

fromEnum :: EventVersion -> Int

enumFrom :: EventVersion -> [EventVersion]

enumFromThen :: EventVersion -> EventVersion -> [EventVersion]

enumFromTo :: EventVersion -> EventVersion -> [EventVersion]

enumFromThenTo :: EventVersion -> EventVersion -> EventVersion -> [EventVersion]

Eq EventVersion

Methods

(==) :: EventVersion -> EventVersion -> Bool

(/=) :: EventVersion -> EventVersion -> Bool

Num EventVersion

Methods

(+) :: EventVersion -> EventVersion -> EventVersion

(-) :: EventVersion -> EventVersion -> EventVersion

(*) :: EventVersion -> EventVersion -> EventVersion

negate :: EventVersion -> EventVersion

abs :: EventVersion -> EventVersion

signum :: EventVersion -> EventVersion

fromInteger :: Integer -> EventVersion

Ord EventVersion

Methods

compare :: EventVersion -> EventVersion -> Ordering

(<) :: EventVersion -> EventVersion -> Bool

(<=) :: EventVersion -> EventVersion -> Bool

(>) :: EventVersion -> EventVersion -> Bool

(>=) :: EventVersion -> EventVersion -> Bool

max :: EventVersion -> EventVersion -> EventVersion

min :: EventVersion -> EventVersion -> EventVersion

Read EventVersion

Methods

readsPrec :: Int -> ReadS EventVersion

readList :: ReadS [EventVersion]

readPrec :: ReadPrec EventVersion

readListPrec :: ReadPrec [EventVersion]

Show EventVersion

Methods

showsPrec :: Int -> EventVersion -> ShowS

show :: EventVersion -> String

showList :: [EventVersion] -> ShowS

ToJSON EventVersion

Methods

toJSON :: EventVersion -> Value

toEncoding :: EventVersion -> Encoding

toJSONList :: [EventVersion] -> Value

toEncodingList :: [EventVersion] -> Encoding

FromJSON EventVersion

Methods

parseJSON :: Value -> Parser EventVersion

parseJSONList :: Value -> Parser [EventVersion]

newtype SequenceNumber

The sequence number gives us a global ordering of events in a particular event store. Using sequence numbers is not strictly necessary for an event sourcing and CQRS system, but it makes it way easier to replay events consistently without having to use distributed transactions in an event bus. In SQL-based event stores, they are also very cheap to create.

Constructors

SequenceNumber

Fields

• unSequenceNumber :: Int

Instances

Enum SequenceNumber

Methods

succ :: SequenceNumber -> SequenceNumber

pred :: SequenceNumber -> SequenceNumber

toEnum :: Int -> SequenceNumber

fromEnum :: SequenceNumber -> Int

enumFrom :: SequenceNumber -> [SequenceNumber]

enumFromThen :: SequenceNumber -> SequenceNumber -> [SequenceNumber]

enumFromTo :: SequenceNumber -> SequenceNumber -> [SequenceNumber]

enumFromThenTo :: SequenceNumber -> SequenceNumber -> SequenceNumber -> [SequenceNumber]

Eq SequenceNumber

Methods

(==) :: SequenceNumber -> SequenceNumber -> Bool

(/=) :: SequenceNumber -> SequenceNumber -> Bool

Num SequenceNumber

Methods

(+) :: SequenceNumber -> SequenceNumber -> SequenceNumber

(-) :: SequenceNumber -> SequenceNumber -> SequenceNumber

(*) :: SequenceNumber -> SequenceNumber -> SequenceNumber

negate :: SequenceNumber -> SequenceNumber

abs :: SequenceNumber -> SequenceNumber

signum :: SequenceNumber -> SequenceNumber

fromInteger :: Integer -> SequenceNumber

Ord SequenceNumber

Methods

compare :: SequenceNumber -> SequenceNumber -> Ordering

(<) :: SequenceNumber -> SequenceNumber -> Bool

(<=) :: SequenceNumber -> SequenceNumber -> Bool

(>) :: SequenceNumber -> SequenceNumber -> Bool

(>=) :: SequenceNumber -> SequenceNumber -> Bool

max :: SequenceNumber -> SequenceNumber -> SequenceNumber

min :: SequenceNumber -> SequenceNumber -> SequenceNumber

Read SequenceNumber

Methods

readsPrec :: Int -> ReadS SequenceNumber

readList :: ReadS [SequenceNumber]

readPrec :: ReadPrec SequenceNumber

readListPrec :: ReadPrec [SequenceNumber]

Show SequenceNumber

Methods

showsPrec :: Int -> SequenceNumber -> ShowS

show :: SequenceNumber -> String

showList :: [SequenceNumber] -> ShowS

ToJSON SequenceNumber

Methods

toJSON :: SequenceNumber -> Value

toEncoding :: SequenceNumber -> Encoding

toJSONList :: [SequenceNumber] -> Value

toEncodingList :: [SequenceNumber] -> Encoding

FromJSON SequenceNumber

Methods

parseJSON :: Value -> Parser SequenceNumber

parseJSONList :: Value -> Parser [SequenceNumber]

ToHttpApiData SequenceNumber

Methods

toUrlPiece :: SequenceNumber -> Text

toEncodedUrlPiece :: SequenceNumber -> Builder

toHeader :: SequenceNumber -> ByteString

toQueryParam :: SequenceNumber -> Text

FromHttpApiData SequenceNumber

Methods

parseUrlPiece :: Text -> Either Text SequenceNumber

parseHeader :: ByteString -> Either Text SequenceNumber

parseQueryParam :: Text -> Either Text SequenceNumber

PathPiece SequenceNumber

Methods

fromPathPiece :: Text -> Maybe SequenceNumber

toPathPiece :: SequenceNumber -> Text

Utility functions

transactionalExpectedWriteHelper :: Monad m => (UUID -> m EventVersion) -> (UUID -> [event] -> m ()) -> ExpectedVersion -> UUID -> [event] -> m (Maybe EventWriteError)

Helper to create storeEventsRaw given a function to get the latest stream version and a function to write to the event store. **NOTE**: This only works if the monad m is transactional.