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thimble 0.1.0

A Twisted thread-pool based wrapper for blocking APIs.

Latest Version: 0.1.1

Assemble is a tool for playing with needle and thread safely. This library, thimble, wraps objects that have a blocking API with a non-blocking, Twisted-friendly Deferred API by means of thread pools.

Quick start

The main object you’re interested in is timble.Thimble. It takes a thread pool, a blocking object, and a list of method names that you would like to defer to the thread pool.

Here’s our example blocking object:

>>> class Car(object):
...     wheels = 4
...     def drive_to(self, location):
...          # Assume the real implementation blocks.
...          return "driven to {0}".format(location)
>>> car = Car()

For demonstration purposes, we’ll use a test doubles for the thread pool and reactor; in real code, you’ll want to use the real thing.

>>> from thimble.test.util import FakeThreadPool, FakeReactor
>>> pool = FakeThreadPool()
>>> reactor = FakeReactor()

The pool hasn’t been started yet. (We’ll see why that matters in a minute.)

>>> pool.started
False

Create a Thimble:

>>> from thimble import Thimble
>>> car_thimble = Thimble(reactor, pool, car, ["drive_to"])

When accessing a method named in the list, you get an object wrapping it instead. Calling it returns a Deferred. Any arguments passed are passed verbatim to the wrapped method.

>>> d = car_thimble.drive_to("work")
>>> d.result
'driven to work'

This Deferred has already fired synchronously, because we’re using a fake thread pool and reactor.

You can access other attributes of the wrapped object directly on the Thimble:

>>> car.wheels
4

If the thread pool that you pass to a Thimble hasn’t been started yet when it first tries to use it, the Thimble will start it and schedule its shutdown. If you pass a thread pool that was already started, you are responsible for its shutdown. In this case, the thread pool was not started yet, so Thimble started it for you:

>>> pool.started
True

Shut down the reactor, and the reactor will ask the thread pool to stop right before shutting down itself.

>>> reactor.stop()
>>> pool.started
False

Using thimble in your code

Thread pools

You can choose to use the reactor thread pool, or create your own thread pool.

Using the reactor thread pool is potentially a bad idea. The reactor thread pool is shared between a lot of software by default, and is also used for DNS resolution. If your software blocks all the available threads in the pool (either by accident or because of a bug), that affects DNS resolution, which in turn can affect many other systems.

Entry points

While subclassing Thimble may accidentally work, it is not recommended. I reserve the right to change the implementation in a way that might break that: for example, by introducing a metaclass.

It’s probably better to write a small utility function that either constructs a new thread pool from a shared thread pool, or always returns the same thimble.

 
File Type Py Version Uploaded on Size
thimble-0.1.0-py27-none-any.whl (md5) Python Wheel py27 2014-05-17 9KB
thimble-0.1.0.tar.gz (md5) Source 2014-05-17 7KB
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