Safe Haskell	None
Language	Haskell2010

Eventful.Store.Class

Contents

EventStore
Serialization
Utility types
Utility functions

Synopsis

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.