What's this

gaedeferred is a module to make deferred chain on Google Appengine. By lack of taskqueue API and ext.deferred design, there is no support for error case handling as errback.

This module is inspired by Twisted.

How to

Follow steps.:

>>> from google.appengine.ext import deferred
>>> from gaedeferred import Deferred

>>> from tests.test_deferred import increase, must_be

>>> d = Deferred()

You can regist a callback.
>>> d.addCallback(increase, 10)

There is alias.
>>> d.next(must_be, 15)

The deferred chain is to be executed in an asynchronous task.
So the function increase will be called with params 5 and 10 later.
>>> deferred.defer(d.callback, 5) # doctest: +ELLIPSIS
<google.appengine.api.taskqueue.taskqueue.Task object at ...>

More details, see tests. Also the tests has how to use DeferredList.

How to test

Use nose with NoseGAE.:

$ nosetests

Or:

$ python setup.py test

To test, this module requires nose and some modules.

• nose
• NoseGAE
• gaetestbed https://github.com/jgeewax/gaetestbed with a patch. https://github.com/jgeewax/gaetestbed/pull/10
• WebTest
• docutils

Note, they will be installed automatically when you run "python setup.py test".

To do

• Consider transaction control of DeferredList doing.

Questions and Bug Reports

• Site https://github.com/jbking/gaedeferred
• Or, cantact me. MURAOKA Yusuke <yusuke@jbking.org>

Changes