pressure

A reimplementation of Python's synchronized and bounded Queue.Queue on a Redis backend.

by Peter Sobot (@psobot, psobot.com). Licensed under MIT.

---

pressure implements everybody's favourite Python data structure, the trusty built-in Queue.Queue, on top of everybody's favourite distributed data store, Redis. Nearly all of the original Queue's API is replicated.

pressure allows for synchronized, blocking and distributed (a.k.a.: multi-process) queues to be shared between processes, between machines, and even between data centers.

pressure is also multilingual - the protocol is well-defined (see protocol.md) and there are libraries already for different languages, all included as submodules of this repo:

• pressure-python
• pressure-c (not submoduled just yet)

Examples

import pressure

#   Create two unique handles to the 'test' queue.
q1 = pressure.PressureQueue('test')
q2 = pressure.PressureQueue('test')

#   Create the 'test' queue, giving a bound of 5.
q1.create(bound=5)

#   Put the strings into one handle.
for string in ["hello", "goodbye"]:
    q1.put(string)

#   Close the queue - assert that no more data will be produced.
q1.close()

#   Receive the strings from the other handle!
for result in q2:
    print result

# Prints:
#   "hello"
#   "goodbye"

#   Delete the queue from the database once its data has been consumed.
#   This should be done on the consumer's end, as the consumer knows
#   once all of the data is gone.
q2.delete()

Get Started

> sudo pip install pressure

# for quick local testing, make sure you have redis-server running
> redis-server &

# muck around with ipython?
> cd python
> ipython

Python 2.7.1 (r271:86832, Jun 16 2011, 16:59:05) 
Type "copyright", "credits" or "license" for more information.

IPython 0.13 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.

In [1]: import pressure
In [2]: q1 = pressure.PressureQueue('test_queue')
In [3]: q1.create(5)
In [4]: q1.put('hello springfield!')

TODOs

- Ensure that this library has 100% API coverage with the original Queue.Queue.
- Clean up and document the internals.

Questions/Comments/Feedback?

This is GitHub after all, so please feel free to open an issue if you discover a bug. Better yet, feel free to fork this repo, add a test to cover the bug, maybe even fix the bug, and send me back a pull request. You'll get a gold star and a very happy tweet from me.

LICENSE and all that jazz

Copyright (c) 2013 Peter Sobot

Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the "Software"),
to deal in the Software without restriction, including without limitation
the rights to use, copy, modify, merge, publish, distribute, sublicense,
and/or sell copies of the Software, and to permit persons to whom the
Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.