Servant.API.EventStream

Server-Sent Events

Event streams are implemented using servant's Stream endpoint. You should provide a handler that returns a stream of events that implements ToSourceIO where events have a ToServerEvent instance.

Example:

type MyApi = "books" :> ServerSentEvents (SourceIO Book)

instance ToServerEvent Book where
  toServerEvent book = ...

server :: Server MyApi
server = streamBooks
  where streamBooks :: Handler (SourceIO Book)
        streamBooks = pure $ source [book1, ...]

data ServerEvent

Represents an event sent from the server to the client in Server-Sent Events (SSE).

Constructors

ServerEvent

Fields

• eventType :: !(Maybe ByteString)

  Optional field specifying the type of event. Can be used to distinguish between different kinds of events.

• eventId :: !(Maybe ByteString)

  Optional field providing an identifier for the event. Useful for clients to keep track of the last received event.

• eventData :: !ByteString

  The payload or content of the event. This is the main data sent to the client.

Instances

Generic ServerEvent

Defined in Servant.API.EventStream

Associated Types

type Rep ServerEvent :: Type -> Type

Methods

from :: ServerEvent -> Rep ServerEvent x

to :: Rep ServerEvent x -> ServerEvent

Show ServerEvent

Defined in Servant.API.EventStream

Methods

showsPrec :: Int -> ServerEvent -> ShowS

show :: ServerEvent -> String

showList :: [ServerEvent] -> ShowS

Eq ServerEvent

Defined in Servant.API.EventStream

Methods

(==) :: ServerEvent -> ServerEvent -> Bool

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

ToServerEvent ServerEvent

Defined in Servant.API.EventStream

Methods

toServerEvent :: ServerEvent -> ServerEvent

type Rep ServerEvent

Defined in Servant.API.EventStream

type Rep ServerEvent = D1 ('MetaData "ServerEvent" "Servant.API.EventStream" "servant-event-stream-0.3.0.1-Ew4vICvJTra6nuiDFTspbH" 'False) (C1 ('MetaCons "ServerEvent" 'PrefixI 'True) (S1 ('MetaSel ('Just "eventType") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 (Maybe ByteString)) :*: (S1 ('MetaSel ('Just "eventId") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 (Maybe ByteString)) :*: S1 ('MetaSel ('Just "eventData") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 ByteString))))

class ToServerEvent a where

This typeclass allows you to define custom event types that can be transformed into the ServerEvent type, which is used to represent events in the Server-Sent Events (SSE) protocol.

Methods

toServerEvent :: a -> ServerEvent

Instances

ToServerEvent ServerEvent

Defined in Servant.API.EventStream

Methods

toServerEvent :: ServerEvent -> ServerEvent

data ServerSentEvents (a :: Type)

A ServerSentEvents endpoint emits an event stream using the format described at https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events/Using_server-sent_events#event_stream_format

Instances

HasForeignType lang ftype a => HasForeign (lang :: k) ftype (ServerSentEvents a)

a helper instance for servant-foreign

Defined in Servant.API.EventStream

Associated Types

type Foreign ftype (ServerSentEvents a)

Methods

foreignFor :: Proxy lang -> Proxy ftype -> Proxy (ServerSentEvents a) -> Req ftype -> Foreign ftype (ServerSentEvents a)

HasLink (ServerSentEvents a :: Type)

Defined in Servant.API.EventStream

Associated Types

type MkLink (ServerSentEvents a) a

Methods

toLink :: (Link -> a0) -> Proxy (ServerSentEvents a) -> Link -> MkLink (ServerSentEvents a) a0

(ToServerEvent chunk, ToSourceIO chunk a, GetHeaders (Headers h a)) => HasServer (ServerSentEvents (Headers h a) :: Type) context

Defined in Servant.API.EventStream

Associated Types

type ServerT (ServerSentEvents (Headers h a)) m

Methods

route :: Proxy (ServerSentEvents (Headers h a)) -> Context context -> Delayed env (Server (ServerSentEvents (Headers h a))) -> Router env

hoistServerWithContext :: Proxy (ServerSentEvents (Headers h a)) -> Proxy context -> (forall x. m x -> n x) -> ServerT (ServerSentEvents (Headers h a)) m -> ServerT (ServerSentEvents (Headers h a)) n

(ToServerEvent chunk, ToSourceIO chunk a) => HasServer (ServerSentEvents a :: Type) context

Defined in Servant.API.EventStream

Associated Types

type ServerT (ServerSentEvents a) m

Methods

route :: Proxy (ServerSentEvents a) -> Context context -> Delayed env (Server (ServerSentEvents a)) -> Router env

hoistServerWithContext :: Proxy (ServerSentEvents a) -> Proxy context -> (forall x. m x -> n x) -> ServerT (ServerSentEvents a) m -> ServerT (ServerSentEvents a) n

Generic (ServerSentEvents a)

Defined in Servant.API.EventStream

Associated Types

type Rep (ServerSentEvents a) :: Type -> Type

Methods

from :: ServerSentEvents a -> Rep (ServerSentEvents a) x

to :: Rep (ServerSentEvents a) x -> ServerSentEvents a

type Foreign ftype (ServerSentEvents a)

Defined in Servant.API.EventStream

type Foreign ftype (ServerSentEvents a) = Req ftype

type MkLink (ServerSentEvents a :: Type) r

Defined in Servant.API.EventStream

type MkLink (ServerSentEvents a :: Type) r = r

type ServerT (ServerSentEvents (Headers h a) :: Type) m

Defined in Servant.API.EventStream

type ServerT (ServerSentEvents (Headers h a) :: Type) m

type ServerT (ServerSentEvents a :: Type) m

Defined in Servant.API.EventStream

type ServerT (ServerSentEvents a :: Type) m

type Rep (ServerSentEvents a)

Defined in Servant.API.EventStream

type Rep (ServerSentEvents a) = D1 ('MetaData "ServerSentEvents" "Servant.API.EventStream" "servant-event-stream-0.3.0.1-Ew4vICvJTra6nuiDFTspbH" 'False) (V1 :: Type -> Type)

data EventStream

A type representation of an event stream. It's responsible for setting proper content-type and buffering headers, as well as for providing parser implementations for the streams. Read more on Servant Streaming Docs

Instances

Accept EventStream

Defined in Servant.API.EventStream

Methods

contentType :: Proxy EventStream -> MediaType

contentTypes :: Proxy EventStream -> NonEmpty MediaType

ToServerEvent a => MimeRender EventStream a

Defined in Servant.API.EventStream

Methods

mimeRender :: Proxy EventStream -> a -> ByteString

Recommended headers for Server-Sent Events

This is mostly to guide reverse-proxies like nginx.

Example:

type MyApi = "books" :> ServerSentEvents (RecommendedEventSourceHeaders (SourceIO Book))

server :: Server MyApi
server = streamBooks
  where streamBooks :: Handler (RecommendedEventSourceHeaders (SourceIO Book))
        streamBooks = pure $ recommendedEventSourceHeaders $ source [book1, ...]

type RecommendedEventSourceHeaders (a :: Type) = Headers '[Header "X-Accel-Buffering" Text, Header "Cache-Control" Text] a

Recommended headers for Server-Sent Events.

recommendedEventSourceHeaders :: a -> RecommendedEventSourceHeaders a

Add the recommended headers for Server-Sent Events to the response.