Network.AMQP.Worker.Message

Documentation

data Message a

a parsed message from the queue

Constructors

Message

Fields

• body :: ByteString
• value :: a

Instances

Show a => Show (Message a)

Defined in Network.AMQP.Worker.Message

Methods

showsPrec :: Int -> Message a -> ShowS

show :: Message a -> String

showList :: [Message a] -> ShowS

Eq a => Eq (Message a)

Defined in Network.AMQP.Worker.Message

Methods

(==) :: Message a -> Message a -> Bool

(/=) :: Message a -> Message a -> Bool

publish :: (RequireRoute a, ToJSON msg, MonadIO m) => Connection -> Key a msg -> msg -> m ()

send a message to a queue. Enforces that the message type and queue name are correct at the type level

let newUsers = key "users" & word "new" :: Key Route User
publish conn newUsers (User "username")

Publishing to a Binding Key results in an error

-- Compiler error! This doesn't make sense
let users = key "users" & many :: Key Binding User
publish conn users (User "username")

publishToExchange :: (RequireRoute a, ToJSON msg, MonadIO m) => Connection -> Key a msg -> msg -> m ()

publish a message to a routing key, without making sure a queue exists to handle it

publishToExchange conn key (User "username")

takeMessage :: (MonadIO m, FromJSON a) => Connection -> Queue a -> m (Message a)

Wait until a message is read from the queue. Throws an exception if the incoming message doesn't match the key type

m <- Worker.takeMessage conn queue
print (value m)

worker :: (FromJSON a, MonadIO m) => Connection -> Queue a -> (Message a -> m ()) -> m ()

Create a worker which loops and handles messages. Throws an exception if the incoming message doesn't match the key type. It is recommended that you catch errors in your handler and allow message parsing errors to crash your program.

Worker.worker conn queue $ \m -> do
  print (value m)

consumeNext :: (FromJSON msg, MonadIO m) => Microseconds -> Connection -> Queue msg -> m (ConsumeResult msg)

Block while checking for messages every N microseconds. Return once you find one.

res <- consumeNext conn queue
case res of
  (Parsed m) -> print m
  (Error e) -> putStrLn "could not parse message"

consume :: (FromJSON msg, MonadIO m) => Connection -> Queue msg -> m (Maybe (ConsumeResult msg))

Check for a message once and attempt to parse it

res <- consume conn queue
case res of
  Just (Parsed m) -> print m
  Just (Error e) -> putStrLn "could not parse message"
  Nothing -> putStrLn "No messages on the queue"

data ConsumeResult a

Constructors

Parsed (Message a)

Error ParseError

data ParseError

Constructors

ParseError String ByteString

Instances

Exception ParseError

Defined in Network.AMQP.Worker.Message

Methods

toException :: ParseError -> SomeException

fromException :: SomeException -> Maybe ParseError

displayException :: ParseError -> String

Show ParseError

Defined in Network.AMQP.Worker.Message

Methods

showsPrec :: Int -> ParseError -> ShowS

show :: ParseError -> String

showList :: [ParseError] -> ShowS

type Microseconds = Int