cipher.background 1.0.2

Background thread support with ZODB support

A library for creating background threads that can talk to the ZODB and use local site components.

We’re probably reinventing Celery.

Example

Let’s assume we have a DMS with a simple publication workflow. We have two states “DRAFT” and “PUBLISH”. The Problem in this example is: that the transition form “DRAFT” to “PUBLISH” takes some minutes, and we don’t want the user to be waiting.

First we have create a WorkflowTransition-BackgroundThread:

class MyWorkflowTransition(BackgroundWorkerThread):
    execute = True
    description = "background worker thread (%(class_name)s) for %(site_name)s User %(user_name)s"

    def __init__(self, site_db, site_oid, site_name, user_name, daemon=True, object_oid=None):
        self.object_oid = object_oid
        super(MyWorker, self).__init__(site_db, site_oid, site_name, user_name, daemon=True)

    def scheduleNextWork(self):
        return self.execute

    def getObjectFromOID(self):
        conn = getSite()._p_jar
        return conn.get(self.object_oid)

    def doWork(self):
        sleep(15) # This is our long TASK
        self.execute = False
        document = self.getObjectFromOID()
        document.wf_status = "PUBLISHED"

We have a simple Document with an initial Workflow-State draft.

class Document(Persistent):
    wf_state = "DRAFT"

Now we have to call our WorkflowTransition.

def setWorkflow(site, document_oid, user_name):
    worker = MyWorkflowTransition(
        site_db = site._p_jar.db(),
        site_oid = site._p_oid,
        site_name = site.__name__,
        user_name = user_name,
        object_oid = document_oid,
        )
    worker.start()

When calling worker.start() the thread goes into “Background” and the user don’t have to wait until the Transition is finished.

CHANGES

1.0.2 (2012-07-31)

• Refactor BackgroundWorkerThread to have the site returned from getSite()

1.0.1 (2012-04-05)

1.0.0 (2012-02-10)

• Initial release as a separate package.