https://github.com/noteed/humming

queue_classic in Haskell
https://github.com/noteed/humming

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queue_classic in Haskell

• Host: GitHub
• URL: https://github.com/noteed/humming
• Owner: noteed
• License: other
• Created: 2013-03-03T22:08:40.000Z (almost 12 years ago)
• Default Branch: main
• Last Pushed: 2024-03-07T11:26:11.000Z (10 months ago)
• Last Synced: 2024-03-07T12:41:10.745Z (10 months ago)
• Language: Haskell
• Size: 65.4 KB
• Stars: 6
• Watchers: 3
• Forks: 1
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# Humming - `queue_classic` in Haskell

Humming implements job queues and time-based job scheduling in Haskell on top

of PostgreSQL. The job queue is a port of the Ruby

[`queue_classic`](https://github.com/QueueClassic/queue_classic) library.

This package also provides a `humming` command-line program to interact with

`queue_classic` or Humming.

## Overview

Humming essentially manages two PostgreSQL tables: one for the queues, and one

for the scheduled jobs.

Jobs can be pushed to (or retrieved from) Humming using any programming

language that can talk to PostgreSQL. In particular, you can use this library

in Haskell, [`queue_classic`](https://github.com/QueueClassic/queue_classic) in

Ruby, or [Pueuey](https://github.com/cecton/pueuey) in Python.

Jobs are scheduled by writing to the scheduled jobs table. Moving scheduled

jobs to Humming queues is done by running the `humming schedule` process.

## Example usage

A `humming` executable is provided.

    > export DB='postgres://username:password@localhost/database'

    > humming create  --database-url $DB

    > humming drop    --database-url $DB

    > humming enqueue --database-url $DB \

        --queue FOO --method play --arguments '{}'

    > humming count   --database-url $DB [--queue FOO]

    > humming delete  --database-url $DB --job 4

    > humming lock    --database-url $DB --queue FOO

    > humming work    --database-url $DB --queue FOO

    > humming schedule --database-url $DB [--queue FOO]

`humming schedule` push endlessly scheduled jobs to their respective queues. It

is possible to take care of only jobs destined to a specific queue with the

`--queue` option. It is safe to run multiple `humming schedule` processes

(possibly on different hosts).

Instead of a `--database-url` option, it is possible to use the

`HUMMING_CONNECTION_STRING` environment variable.

## Tests

Tests can be run withing GHCi with the `runTests` function.

## Limitations

- Uses `procpid` from `pg_stat_activity` which was renamed `pid` in PostgreSQL

  9.2.

- Probably doesn't reconnect after a connection error.

- It should be possible to pass --database-url value via a file.

- The table holding the jobs is hard-coded to `queue_classic_jobs`.

- Not much logging is done (and actually only stdout is used).

- Need to handle signals.

- Doesn't handle more than one queue per worker.