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Integration package for zc.async allowing asynchronous operations in Plone

Project description

===============
plone.app.async
===============

Introduction
============
Integration package for `zc.async`_ allowing asynchronous operations in
Plone 3 and 4.

Installation
============
You will typically run ``plone.app.async`` in a ZEO environment, where you
will have one or more *worker* instances carrying out jobs queued by your
main zope instances.

For the sake of simplicity it is assumed that you have one instance that can
queue new jobs, and one worker instance that consumes them, both operating on
a single database. In this case your buildout configuration will look similar
to the following::

[zeo]
recipe = plone.recipe.zope2zeoserver
file-storage = ${buildout:directory}/var/filestorage/Data.fs

[instance]
recipe = plone.recipe.zope2instance
eggs = Plone plone.app.async
zcml =
zcml-additional =
<include package="plone.app.async" file="single_db_instance.zcml" />
environment-vars =
ZC_ASYNC_UUID ${buildout:directory}/var/instance-uuid.txt

[worker]
recipe = plone.recipe.zope2instance
eggs = ${instance:eggs}
zcml = ${instance:zcml}
zcml-additional =
<include package="plone.app.async" file="single_db_worker.zcml" />
environment-vars =
ZC_ASYNC_UUID ${buildout:directory}/var/worker-uuid.txt

There are two important stanzas here:

* Each instance has to set the ``ZC_ASYNC_UUID`` environment variable in order
to integrate properly with `zc.async`_.

* Each instance loads the ``single_db_instance.zcml`` configuration.
The worker instance loads the ``single_db_worker.zcml`` configuration
in order to setup the queue and configure itself as a dispatcher.

For more details please look at the `example buildout configurations`_ included in
the package.

.. _`example buildout configurations`: http://dev.plone.org/plone/browser/plone.app.async/trunk


Plone 3
-------

Use zope.app.keyreference


Plone 4
-------

Use five.intid


Credits
=======
Code from Enfold's `plone.async.core`_ package has been used for setting up the queues.

References
==========
* `zc.async`_ on PyPI
* `plone.async.core`_ Subversion repository

.. _zc.async: http://pypi.python.org/pypi/zc.async
.. _plone.async.core: https://svn.enfoldsystems.com/public/plone.async.core


User Documentation
==================

Basic use
---------

Assuming your setup is done correctly, you can start by obtaining the
``AsyncService`` utility::

>>> from zope.component import getUtility
>>> from plone.app.async.interfaces import IAsyncService
>>> async = getUtility(IAsyncService)
>>> async
<plone.app.async.service.AsyncService object at ...>
>>> folder = layer['test-folder']
>>> portal = layer['portal']

You can already get the ``zc.async`` queues::

>>> async.getQueues()
<zc.async.queue.Queues object at ...>

>>> import zc.async.dispatcher
>>> from plone.app.async.testing import _dispatcher_uuid
>>> zc.async.dispatcher.get(_dispatcher_uuid)
<zc.async.dispatcher.Dispatcher object at ...>
>>> queue = async.getQueues()['']
>>> queue
<zc.async.queue.Queue object at ...>

Let's define a simple function to be executed asynchronously. Note that the
first argument **must** be a valid Zope object::

>>> from plone.app.async.tests.funcs import *

and queue it::

>>> job = async.queueJob(addNumbers, folder, 40, 2)
>>> len(queue)
1
>>> job.status
u'pending-status'


In real life the job would be executed by the worker. In the tests we need
to commit in order to let the dispatcher become aware of the job and
execute it. Also we wait for the job to complete before continuing with the
test::

>>> import transaction
>>> from zc.async.testing import wait_for_result
>>> transaction.commit()
>>> wait_for_result(job)
42

Batches of jobs
---------------

Let's now try some jobs that create persistent objects. First define
the tasks to be executed asynchronously::

and::

>>> from Products.CMFCore.utils import getToolByName


Queue a job that creates a document and another that submits it::

>>> job = async.queueJob(createDocument, folder,
... 'foo', 'title', 'description', 'body')
>>> job2 = async.queueJob(submitObject, folder, 'foo')
>>> transaction.commit()

Because by default the jobs are executed with the default quota set to 1,
(i.e. only one job can be executed at a time), jobs are executed serially and
according to the order by which they were submitted. Hence, waiting for the
job that submits the document implies that the one that created it has already
been carried out::

>>> wait_for_result(job2)
>>> wt = getToolByName(folder, 'portal_workflow')
>>> doc = folder['foo']
>>> wt.getInfoFor(doc, 'review_state')
'pending'

You can also queue a *batch* of jobs to be executed serially as one job by use
of ``queueSerialJobs``::

>>> from plone.app.async.service import makeJob
>>> job = async.queueSerialJobs(
... makeJob(createDocument, folder,
... 'bar', 'title', 'description', 'body'),
... makeJob(submitObject, folder, 'bar'))
>>> transaction.commit()
>>> res = wait_for_result(job)
>>> res[0].result
'bar'
>>> res[1].status
u'completed-status'
>>> doc = folder['bar']
>>> wt.getInfoFor(doc, 'review_state')
'pending'

If you want to execute jobs in parallel, you can use ``queueParallelJobs``.

Security and user permissions
-----------------------------

When a job is queued by some user, it is also executed by the same user, with
the same roles and permissions. So for instance::

>>> job = async.queueJob(createDocument, portal,
... 'foo', 'title', 'description', 'body')
>>> transaction.commit()

will fail as the user is not allowed to create content in the Plone root::

>>> wait_for_result(job)
<...Unauthorized...

Handling failure and success
----------------------------

If you need to act on the result of a job or handle a failure you can do
so by adding callbacks. For instance::

>>> from plone.app.async.tests import funcs
>>> job = async.queueJob(addNumbers, folder, 40, 2)
>>> c = job.addCallback(job_success_callback)
>>> transaction.commit()
>>> r = wait_for_result(job)
>>> funcs.results
['Success: 42']

Failures can be handled in the same way::

>>> job = async.queueJob(failingJob, folder)
>>> c = job.addCallbacks(failure=job_failure_callback)
>>> transaction.commit()
>>> r = wait_for_result(job)
>>> funcs.results
[...RuntimeError...

It is also possible to handle all successful/failed jobs (for instance if you
want to send an email upon failure) by subscribing to the respective event::

>>> from zope.component import provideHandler
>>> from plone.app.async.interfaces import IJobSuccess, IJobFailure
>>> provideHandler(successHandler, [IJobSuccess])
>>> provideHandler(failureHandler, [IJobFailure])
>>> funcs.results = []
>>> job1 = async.queueJob(addNumbers, folder, 40, 2)
>>> job2 = async.queueJob(failingJob, folder)
>>> transaction.commit()
>>> r = wait_for_result(job2)
>>> funcs.results
[42, ...RuntimeError...FooBared...

Let's clean up and unregister the success/failure handlers...::

>>> from zope.component import getGlobalSiteManager
>>> gsm = getGlobalSiteManager()
>>> _ = gsm.unregisterHandler(successHandler, [IJobSuccess])
>>> _ = gsm.unregisterHandler(failureHandler, [IJobFailure])
>>> transaction.commit()


Changelog
=========

1.3 (2012-10-05)
----------------

- buildout infrastructure refresh [kiorky]
- plone 4.3 compatibility [kiorky]
- Switch tests from collective.testcaselayer to plone.app.testing [kiorky]
- Merge expemimental work on UI & jobs back to master
[kiorky]
- Add plone UI to view jobs
[davisagli]
- Added support for queued/deferred tasks.
[kiork,davisagli,do3cc]


1.2 - 2012-04-26
----------------

- Fix includes to work correctly with dexterity and
to include simplejson.
[vangheem]

- Change ping intervals to something more sane so it doesn't
take so long for your workers to come back online after restart.
[vangheem]


1.1 - 2011-07-21
----------------

- Add MANIFEST.in.
[WouterVH]

- Change zcml:condition for zope.(app.)keyreference to use the plone-4
feature.
[vangheem]

- Always use loadZCMLFile in testcase layers to not break under Zope 2.13.
[stefan]

- Avoid excessive ZODB growth by increasing the dispatcher ping intervals.
https://mail.zope.org/pipermail/zope-dev/2011-June/043146.html
[stefan]


1.0 - 2011-01-03
----------------

- Conditionally include zope.app.keyreference ZCML.
[vangheem]

- Fix for async jobs started by anonymous user.
[naro]

- Add full set of example buildouts.
[stefan]

- Make tests pass under Plone 3 and 4. Exception representations have changed
for some odd reason.
[stefan]


1.0a6 - 2010-10-14
------------------

- First public release.
[ggozad]


1.0a5 - 2010-10-14
------------------

- Instead of guessing where a userid may be coming from, record the path
of the userfolder and use that to reinstate the user.
[mj]


1.0a4 - 2010-09-09
------------------

- Use multi-db setup in tests to keep testcaselayer working as expected.
[stefan, ggozad]


1.0a3 - 2010-09-01
------------------

- Separate helper function from test setup so it can be used in non-test code.
[witsch]


1.0a2 - 2010-08-30
------------------

- Made separate zcml configurations for single/multi and instance/worker.
[stefan, ggozad]


1.0a1 - 2010-08-25
------------------

- zc.async integration for Plone. Initial release.
[ggozad, stefan]

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