This module utilizes PostgreSQL to implement a durable queue for efficently processing arbitrary payloads which can be represented as JSON.
Typically a producer would enqueue a new payload as part of larger database transaction
createAccount userRecord = do runDBTSerializable $ do createUserDB userRecord enqueueDB $ makeVerificationEmail userRecord
In another thread or process, the consumer would drain the queue.
forever $ do -- Attempt get a payload or block until one is available payload <- lock conn -- Perform application specifc parsing of the payload value case fromJSON $ pValue payload of Success x -> sendEmail x -- Perform application specific processing Error err -> logErr err -- Remove the payload from future processing dequeue conn $ pId payload
stack install postgresql-simple-queue
This package was discussed in the blog Testing PostgreSQL for Fun