Franck Cuny @franckcuny

Software and Operation engineer.

presque, a Redis / Tatsumaki based message queue

presque is a small message queue service build on top of redis and Tatsumaki. It's heavily inspired by RestMQ and resque.

  • Communications are done in JSON over HTTP
  • Queues and messages are organized as REST resources
  • A worker can be writen in any language that make a HTTP request and read JSON
  • Thanks to redis, the queues are persistent

Overview

resque need a configuration file, writen in YAML that contains the host and port for the Redis server.

redis:
    host: 127.0.0.1
    port: 6379

Let's start the server:

% plackup app.psgi --port 5000

The applications provides some HTTP routes:

  • /: a basic HTML page with some information about the queues
  • /q/: REST API to get and post job to a queue
  • /j/: REST API to get some information about a queue
  • /control/: REST API to control a queue (start or stop consumers)
  • /stats/: REST API to fetch some stats (displayed on the index page)

Queues are created on the fly, when a job for an unknown queue is inserted. When a new job is created, the JSON send in the POST will be stored "as is". There is no restriction on the schema or the content of the JSON.

Creating a new job simply consist to :

% curl -X POST "http://localhost:5000/q/foo" -d '{"foo":"bar", "foo2":"bar" }'

and fetching the job:

% curl "http://localhost:5000/q/foo"

When a job is fetched, it's removed from the queue.

A basic worker

I've also pushed presque::worker. It's based on AnyEvent::HTTP and Moose. Let's write a basic worker using this class:

use strict;
use warnings;
use 5.012;    # w00t

package simple::worker;
use Moose;
extends 'presque::worker';

sub work {
    my ($self, $job) = @_;
    say "job's done";
    ...;      # yadda yadda!
    return;
}

package main;
use AnyEvent;

my $worker =
    simple::worker->new(base_uri => 'http://localhost:5000', queue => 'foo');

AnyEvent->condvar->recv;

A worker have to extends the presque::worker class, and implement the method work. When the object is created, the class check if this method is avalaible. You can also provide a fail method, which will be called when an error occur.

The future

I plan to add support for websocket, and probably XMPP. More functionalities to the worker too: logging, forking, handling many queues, ... I would like to add priorities to queue also, and maybe scheluding job for a given date (not sure if it's feasable with Redis).