Event Framework
jobs will be reclassified as standard jobs and subsequently executed. When scheduling a job, if jobs of the same type already exist, the new job will be placed at the end of the list of jobs of the same type.
To schedule a job the dispatcher member function "schedule()" must be called, supplying the call- back function and the type of job. To set the dispatcher running, the member function "run()" is called. If the only feature of the event system which is used is that of scheduling jobs, the "run()" function will return when there are no more jobs to execute. A job may prematurely stop the dispatcher by calling the "stop()" member function. If a callback raises an exception which is not caught and processed within the callback itself, the details of the exception will be logged, the dispatcher stopped and Python exited immediately.
def callback(message="hi"): print message
dispatcher = netsvc.Dispatcher() dispatcher.schedule(callback,netsvc.IDLE_JOB) dispatcher.schedule(callback,netsvc.STANDARD_JOB) dispatcher.schedule(callback,netsvc.PRIORITY_JOB) dispatcher.run()
The callback supplied when scheduling a job can be a normal function or a member function associated with an instance of a class. If a callback function is scheduled directly with the dispatcher in this way, it will be called with no arguments and cannot be cancelled once scheduled.
If it is necessary to pass arguments to a callback function, an instance of the Job class must be used in place of the actual callback function. The Job class will hold a reference to the real callback func- tion as well as the arguments. When the job is executed it will call the callback function with the sup- plied arguments.
job = netsvc.Job(callback,("bye",)) dispatcher.schedule(job,netsvc.IDLE_JOB)
In addition to providing a means of supplying arguments to a callback function, the Job class provides a means of cancelling execution of a callback function. In order to do this, a reference to the instance of the Job class should be kept. If it is subsequently necessary to cancel execution of the callback prior to it having being called, the "cancel()" member function of the Job class should be called.
job = None
def callback1(): print "hi" job.cancel()
def callback2(): print "hi"
dispatcher.schedule(callback1,netsvc.PRIORITY_JOB) job = netsvc.Job(callback2) dispatcher.schedule(job,netsvc.STANDARD_JOB)
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