BSD-3-Clause licensed by Jonathan Fischoff
Maintained by [email protected]
This version can be pinned in stack with:postgresql-simple-queue-0.5.0.1@sha256:6f290fe70af5fc00bafc20cf695f0dadf78d7f9d193e8e1a80b9dd6d53e55880,2789

Module documentation for 0.5.0.1

postgresql-simple-queue

This module utilize 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

Installation

stack install postgresql-simple-queue

Blog

This package was discussed in the blog Testing PostgreSQL for Fun