Overview

Event driven concurrent framework for python. Tested in Windows and Linux, it requires python 2.6, 2.7, 3.2, 3.3 or pypy. With pulsar you can write asynchronous servers performing one or several activities in different threads and/or processes.

CI: Documentation:http://packages.python.org/pulsar/ Dowloads:http://pypi.python.org/pypi/pulsar Source:https://github.com/quantmind/pulsar Keywords:server, asynchronous, concurrency, actor, thread, process, socket, task queue

An example of a web server written with pulsar application framework which responds with “Hello World!” for every request:

from pulsar.apps import wsgi

def hello(environ, start_response):
    '''Pulsar HTTP "Hello World!" application'''
    data = b'Hello World!\n'
    status = '200 OK'
    response_headers = [
        ('Content-type','text/plain'),
        ('Content-Length', str(len(data)))
    ]
    start_response(status, response_headers)
    return [data]


if __name__ == '__main__':
    wsgi.WSGIServer(callable=hello).start()

Pulsar’s goal is to provide an easy way to build scalable network programs. In the “Hello world!” web server example above, many client connections can be handled concurrently. Pulsar tells the operating system (through epoll or select) that it should be notified when a new connection is made, and then it goes to sleep.

Pulsar uses the multiprocessing module from the standard python library and it can be configured to run in multi-processing mode, multi-threading mode or a combination of the two.

Installing

Pulsar is a stand alone python library and it can be installed via pip:

pip install pulsar

easy_install or downloading the tarball from pypi.

Applications

Pulsar design allows for a host of different applications to be implemented in an elegant and efficient way. Out of the box it is shipped with the the following

• Socket servers.
• WSGI server.
• JSON-RPC WSGI middleware.
• Web Sockets WSGI middleware.
• Distributed task queue.
• Shell for asynchronous scripting.
• Asynchronous test suite.

Examples

Check out the examples directory for various working applications created using pulsar alone. It includes:

• Hello world! wsgi example.
• An Httpbin wsgi application (similar to http://httpbin.org/).
• An HTTP Proxy server with headers middleware.
• A simple JSON-RPC Calculator server.
• A taskqueue application with a JSON-RPC interface.
• Websocket graph.
• The dining philosophers problem.
• Asynchronous shell.

Design

Pulsar internals are based on actors primitive. Actors are the atoms of pulsar’s concurrent computation, they do not share state between them, communication is achieved via asynchronous inter-process message passing, implemented using the standard python socket library.

Two special classes of actors are the Arbiter, used as a singleton, and the Monitor, a manager of several actors performing similar functions. The Arbiter runs the main eventloop and it controls the life of all actors. Monitors manage group of actors performing similar functions, You can think of them as a pool of actors.

More information about design and philosophy in the documentation.

Add-ons

Pulsar checks if some additional libraries are available, either during installation or at runtime, and uses them to add new functionalities.

• setproctitle: if installed, pulsar can use it to change the processes names of the running application.
• psutil: if installed, a system key is available in the dictionary returned by Actor info method.

Running Tests

Pulsar test suite uses the pulsar test application. If you are using python 2.6 you need to install unittest2, and if not running on python 3.3, the mock library is also needed. To run tests:

python runtests.py

For options and help type:

python runtests.py -h

For full coverage run tests with the following flags:

python runtests.py --concurrency thread --profile --benchmark --http-py-parser --verbosity 2

Kudos

Pulsar project started as a fork of gunicorn (from where the arbiter idea) and has been developed using ideas from nodejs (api design), twisted (the deferred implementation), tornado web server (the event-loop implementation), celery (the task queue application) and many other open-source efforts.

Contributing

Development of pulsar happens at Github. We very much welcome your contribution of course. To do so, simply follow these guidelines:

1. Fork pulsar on github
2. Create a topic branch git checkout -b my_branch
3. Push to your branch git push origin my_branch
4. Create an issue at https://github.com/quantmind/pulsar/issues with a link to your patch.

License

This software is licensed under the New BSD License. See the LICENSE file in the top distribution directory for the full license text.