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spinoff 0.5.4

Framework for writing distributed, fault tolerant and scalable applications

Latest Version: 0.7.18

Overview
========

Spinoff is a framework for writing distributed, fault tolerant and scalable applications in Python.
Spinoff is based on the `Actor Model <http://en.wikipedia.org/wiki/Actor_model>`_ and borrows from `Akka <http://akka.io>`_ (location transparency, actor references, etc)
and `Erlang <http://en.wikipedia.org/wiki/Erlang_(programming_language)>`_ (processes, ``nodename@hosthost`` style node references (not implemented yet)).

Spinoff has been built using `Twisted <twistedmatrix.com>`_ as the underlying framework and `ZeroMQ <http://www.zeromq.org/>`_ (via ``pyzmq`` and a fork of ``txzmq``) for remoting.

Spinoff is currently under continuous development but is nevertheless usable for writing real applications—its fault tolerance features also protect it against bugs in its own code.


Example
=======

The following is only a very small "peek preview" style example of what the framework can do. More examples and full documentation will follow soon.

::

    # spinoff/examples/example1.py

    from spinoff.actor import Actor
    from spinoff.actor.process import Process
    from spinoff.util.logging import dbg
    from spinoff.util.async import sleep, with_timeout


    class ExampleProcess(Process):
        def run(self):
            child = self.spawn(ExampleActor)

            while True:
                dbg("sending greeting to %r" % (child,))
                child << ('hello!', self.ref)

                dbg("waiting for ack from %r" % (child,))
                yield with_timeout(5.0, self.get('ack'))

                dbg("got 'ack' from %r; now sleeping a bit..." % (child,))
                yield sleep(1.0)


    class ExampleActor(Actor):
        def pre_start(self):
            dbg("starting")

        def receive(self, msg):
            content, sender = msg
            dbg("%r from %r" % (content, sender))
            sender << 'ack'

        def post_stop(self):
            dbg("stopping")


The example can be run using the following command:

::

    twistd --nodaemon startnode --actor spinoff.examples.example1.ExampleProcess


Distributed Example (with Remoting)
===================================

::

    # spinoff/examples/example2.py

    class ExampleProcess(Process):
        def run(self, other_actor):
            other_actor = lookup(other_actor) if isinstance(other_actor, str) else other_actor
            while True:
                dbg("sending greeting to %r" % (other_actor,))
                other_actor << ('hello!', self.ref)

                dbg("waiting for ack from %r" % (other_actor,))
                yield with_timeout(5.0, self.get('ack'))

                dbg("got 'ack' from %r; now sleeping a bit..." % (other_actor,))
                yield sleep(1.0)


    class ExampleActor(Actor):
        def pre_start(self):
            dbg("starting")

        def receive(self, msg):
            content, sender = msg
            dbg("%r from %r" % (content, sender))
            sender << 'ack'

        def post_stop(self):
            dbg("stopping")


The example can be run using the following commands:

::

    twistd --pidfile node1.pid --nodaemon startnode --remoting 127.0.0.1:9700 --actor spinoff.examples.example2.ExampleActor --name other
    twistd --pidfile node2.pid --nodaemon startnode --remoting 127.0.0.1:9701 --actor spinoff.examples.example2.ExampleProcess --params "other_actor='127.0.0.1:9700/other'"


Same Distributed Code without Remoting
======================================

The following example demonstrates how it's possible to run the same
code, unmodified, in a single thread with no network/remoting involved
whatsoever.  It's an illustration of how actors (components) written
using Spinoff are agnostic of how they are wired to work with other
actors and can thus be viewed as abstract components containing only
pure domain logic and no low level transportation and topology
details.

::

    # spinoff/examples/example2_local.py

    from spinoff.actor.process import Process
    from spinoff.util.logging import dbg

    from .example2 import ExampleProcess, ExampleActor


    class LocalApp(Process):
        def run(self):
            dbg("spawning ExampleActor")
            actor1 = self.spawn(ExampleActor)

            dbg("spawning ExampleProcess")
            self.spawn(ExampleProcess.using(other_actor=actor1))

            yield self.get()  # so that the entire app wouldn't exit immediately

The example can be run using the following commands:

::

    twistd --nodaemon startnode --actor spinoff.examples.example2_local.LocalApp


One might be tempted to ask, then, what is the difference between
remoting frameworks such as CORBA.  The difference is that actors
define clear boundaries where remoting could ever be used, as opposed
to splitting a flow of tightly coupled logic into two nodes on the
network, which, still providing valid output, can degrade in
performance significantly.  This is not to say that actors with
location transparency suffer none of such issues but the extent to
which the problem exists is, arguably, an order of magnitude lower.
 
File Type Py Version Uploaded on Size
spinoff-0.5.4.tar.gz (md5) Source 2012-11-21 79KB
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