Safe Haskell	None
Language	Haskell2010

Hasql.Queue.High.AtLeastOnce

Synopsis

enqueue :: Connection -> Value a -> [a] -> IO ()
withDequeue :: Connection -> Value a -> Int -> Int -> ([a] -> IO b) -> IO (Maybe b)
failures :: Connection -> Value a -> Maybe PayloadId -> Int -> IO [(PayloadId, a)]
delete :: Connection -> [PayloadId] -> IO ()
withDequeueWith :: forall e a b. Exception e => Connection -> Value a -> Int -> Int -> ([a] -> IO b) -> IO (Maybe b)

Documentation

enqueue Source #

Arguments

:: Connection	Connection
-> Value a	Payload encoder
-> [a]	List of payloads to enqueue
-> IO ()

Enqueue a list of payloads.

withDequeue Source #

Arguments

:: Connection	Connection
-> Value a	Payload decoder
-> Int	Retry count
-> Int	Element count
-> ([a] -> IO b)	Continuation
-> IO (Maybe b)

Wait for the next payload and process it. If the continuation throws an exception the payloads are put back in the queue. IOError is caught and withDequeue will retry up to the retry count. If withDequeue fails after too many retries the final exception is rethrown. If individual payloads are are attempted more than the retry count they are set as "failed". See failures to receive the list of failed payloads.

If the queue is empty withDequeue return Nothing. If there are any entries withDequeue will wrap the list in Just.

failures Source #

Arguments

:: Connection
-> Value a	Payload decoder
-> Maybe PayloadId	Starting position of payloads. Pass `Nothing` to start at the beginning
-> Int	Count
-> IO [(PayloadId, a)]

Retrieve the payloads that have entered a failed state. See withDequeue for how that occurs. The function returns a list of values and an id. The id is used the starting place for the next batch of values. If Nothing is passed the list starts at the beginning.

delete :: Connection -> [PayloadId] -> IO () Source #

Permantently remove a failed payload.

withDequeueWith Source #

Arguments

:: Exception e
=> Connection	Connection
-> Value a	Payload decoder
-> Int	Retry count
-> Int	Element count
-> ([a] -> IO b)	Continuation
-> IO (Maybe b)

A more general configurable version of withDequeue. Unlike withDequeue one can specify the exception that causes a retry. Additionally event handlers can be specified to observe the internal behavior of the retry loop.