# 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
```haskell
createAccount userRecord = do
runDBTSerializable $ do
createUserDB userRecord
enqueueDB $ makeVerificationEmail userRecord
```
In another thread or process, the consumer would drain the queue.
```haskell
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
```bash
stack install postgresql-simple-queue
```
## Blog
This package was discussed in the blog [Testing PostgreSQL for Fun](https://medium.com/@jonathangfischoff/testing-postgresql-for-fun-af891047e5fc)