Integration package for zc.async allowing asynchronous operations in Plone

Project Description


Integration package for zc.async allowing asynchronous operations in Plone 3 and 4.


You will typically run in a ZEO environment, where you will have one or more worker instances that act as dispatchers 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:

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

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

recipe = plone.recipe.zope2instance
eggs = ${instance:eggs}
zcml = ${instance:zcml}
zcml-additional =
    <include package="" 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.


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


User Documentation

Basic use

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

>>> from zope.component import getUtility
>>> from import IAsyncService
>>> async = getUtility(IAsyncService)
>>> async
< object at ...>

You can already get the zc.async queues:

>>> async.getQueues()
<zc.async.queue.Queues object at ...>
>>> import zc.async.dispatcher
>>> zc.async.dispatcher.get()
<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:

>>> def addNumbers(context, x1, x2):
...     return x1+x2

and queue it:

>>> job = async.queueJob(addNumbers, self.folder, 40, 2)
>>> len(queue)
>>> job.status

In real life the job would be exectuted 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)

Batches of jobs

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

>>> def createDocument(context, id, title, description, body):
...     context.invokeFactory('Document', id,
...         title=title, description=description, text=body)
...     return context[id].id


>>> from Products.CMFCore.utils import getToolByName
>>> def submitObject(context, id):
...     obj = context[id]
...     wt = getToolByName(context, 'portal_workflow')
...     wt.doActionFor(obj, 'submit')

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

>>> job = async.queueJob(createDocument, self.folder,
...     'foo', 'title', 'description', 'body')
>>> job2 = async.queueJob(submitObject, self.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(self.folder, 'portal_workflow')
>>> doc = self.folder['foo']
>>> wt.getInfoFor(doc, 'review_state')

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

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

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, self.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)
<zc.twist.Failure AccessControl.unauthorized.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,

>>> results = []
>>> def job_success_callback(result):
...     results.append("Success: %s"%result)
>>> job = async.queueJob(addNumbers, self.folder, 40, 2)
>>> c = job.addCallback(job_success_callback)
>>> transaction.commit()
>>> r = wait_for_result(job)
>>> results
['Success: 42']

Failures can be handled in the same way.

>>> results = []
>>> def failingJob(context):
...     raise RuntimeError("FooBared")
>>> def job_failure_callback(result):
...     results.append(result)
>>> job = async.queueJob(failingJob, self.folder)
>>> c = job.addCallbacks(failure=job_failure_callback)
>>> transaction.commit()
>>> r = wait_for_result(job)
>>> results
[<zc.twist.Failure exceptions.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:

>>> def successHandler(event):
...     results.append(event.object)
>>> def failureHandler(event):
...     exc = event.object
...     results.append("%s: %s" % (exc.type, exc.value))
>>> from zope.component import provideHandler
>>> from import IJobSuccess, IJobFailure
>>> provideHandler(successHandler, [IJobSuccess])
>>> provideHandler(failureHandler, [IJobFailure])
>>> results = []
>>> job1 = async.queueJob(addNumbers, self.folder, 40, 2)
>>> job2 = async.queueJob(failingJob, self.folder)
>>> transaction.commit()
>>> r = wait_for_result(job2)
>>> results
[42, 'exceptions.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])


1.1 - 2011-07-21

  • Add [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. [stefan]

1.0 - 2011-01-03

  • Conditionally include 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]


[ ] Internationalized

[X] Unit tests

[X] End-user documentation

[X] Internal documentation (documentation, interfaces, etc.)

[ ] Existed and maintained for at least 6 months

[ ] Installs and uninstalls cleanly

[X] Code structure follows best practice

Current Release 1.1

Released Jul 21, 2011

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If you are using Plone 3.2 or higher, you probably want to install this product with buildout. See our tutorial on installing add-on products with buildout for more information.

All Releases

Version Released Description Compatibility Licenses Status
1.1 Jul 21, 2011 More about this release… GPL version 2 final
1.0a6 More about this release… GPL version 2 pre-release
1.0 Jan 03, 2011 - More about this release…
Plone 4
GPL final