mongoqueue
----------

Properties
==========

 - Isolation

   Do not let different consumers process the same message.

 - Reliablity

   Do not let a failed consumer disappear an item.

 - Atomic

   Operations on the queue are atomic.

Usage
=====

A queue can be instantiated with a mongo collection and a consumer
identifier. The consumer identifier helps distinguish multiple queue
consumers that are taking jobs from the queue.

  >> from pymongo import Connection
  >> from mongoqueue import MongoQueue
  >> queue = MongoQueue(
  ...   Connection(TEST_DB).doctest_queue,
  ...   consumer_id="consumer-1",
  ...   timeout=300,
  ...   max_attempts=3)

The ``MongoQueue`` class ``timeout`` parameters specifies how long in a
seconds a how long a job may be held by a consumer before its
considered failed.

A job which timeouts or errors more than the ``max_attempts``
parameter is considered permanently failed, and will no longer be
processed.

New jobs/items can be placed in the queue by passing a dictionary.

  >> queue.put({"foobar": 1})

A job ``priority`` key and integer value can be specified in the
dictionary which will cause the job to be processed before lower
priority items.

  >> queue.put({"foobar": 0, "priority": 1})

An item can be fetched out by calling the ``next`` method on a queue.
This returns a Job object.

  >> job = queue.next()
  >> job.data
  {"foobar": 1}

The job class exposes some control methods on the job, for marking progress,
completion, errors, or releasing the job back into the queue.

  - ``complete`` Marks a job as complete and removes it from the queue.

  - ``error`` Optionally specified with a message, releases the job back to the
     queue, and increments its attempts, and stores the error message on the job.

  - ``progress`` Optionally takes a progress count integer, notes progress on the job
     and resets the lock timeout.

  - ``release`` Release a job back to the pool. The attempts counter is not modified.

As a convience the job supports the context manager protocol.

  >> with job as data:
  ...   print data

  {"foobar: 0}

If the context closure is exited without the job is marked complete,
if there's an exception the error is stored on the job.


Inspired By
===========

[0] https://github.com/skiz/mongo_queue/blob/master/lib/mongo_queue.rb
[1] http://blog.boxedice.com/2011/09/28/replacing-rabbitmq-with-mongodb/
[2] http://blog.boxedice.com/2011/04/13/queueing-mongodb-using-mongodb/
[3] https://github.com/lunaru/mongoqueue
[4] http://www.captaincodeman.com/2011/05/28/simple-service-bus-message-queue-mongodb/


Running Tests
=============

Unit tests can be run with

 $ python setup.py nosetests

Changes
=======

0.5.2 - Dec 9th, 2012 - Fix for regression in sort parameters from pymongo 2.4
0.5.1 - Dec 2nd, 2012 - Packaging fix for readme data file.

Credits
=======

Kapil Thangavelu, author & maintainer
Dustin Laurence, sort fix for pymongo 2.4
