class TaskRunner(object):
def __init__(self, concurrency):
"""Create the task runner.
Args:
concurrency: the maximum number of tasks that can run in parallel
"""
self.concurrancy = concurrency
self.task_d = {} # Used to query task status
self.workers_l = []
self.task_q = Queue()
self.stop_flag = False # Used to stop the task pool
self.task_id = 1
# Setup a thread pool of size concurrency
for i in range(self.concurrancy):
self.thread = Thread(target=self.__worker)
self.thread.setDaemon(True)
self.workers_l.append(self.thread)
def add_task(self, task):
"""Adds a task to the task pool.
This may be called whether or not the task pool is currently running.
Args:
task: a Task object
Returns:
the task id associated with the task
"""
# Add task to task dictionary so we can query status later
self.task_d[self.task_id] = task
self.task_id += 1
# Places into task queue, asynchronously
self.task_q.put(task)
return self.task_id-1
def start(self):
"""Asynchronously starts the task pool.
This should cause the TaskRunner to begin executing tasks, however, it does
not need to wait for execution to begin in order to return.
"""
self.thread.start()
def stop(self):
"""Synchronously stops the task pool.
This function should wait until all running (but not queued) tasks have
completed before returning.
"""
self.stop_flag = True
def status(self, task_id):
"""Get the status of a given task.
Args:
task_id: the task id returned by add_task
Returns:
TaskStatus object for the given task
"""
if task_id in self.task_d:
task = self.task_d[task_id]
return task.get_task_status_object()
def cleanup(self, task_id):
"""Removes the task status from the task runner if the task has completed
Args:
task_id: the task id returned by add_task
"""
#TODO: Not sure what this method is trying to do?
self.task_q.quit()
def tasks(self, state=None):
"""Returns metadata regarding tasks currently added to the task pool.
Args:
state: a task state (see TaskStatus for enum defs) to filter for if
specified, if not specified, return data regarding all tasks
Returns:
a list of (task_id, state, queue_position, task) defined as:
task_id: the task id returned by add_task
state: the state of the task (queued, running, complete)
queue_position: the position of the task in the queue
task: the task object
"""
pass
# OPTIONAL - you may skip implementation of this function
def wait(self):
"""OPTIONAL) Wait for all tasks added to the task pool to execute.
"""
# Wait for all tasks to be completed
self.task_q.join()
# OPTIONAL - you may skip implementation of this function
def cancel_task(self, task_id):
"""Cancels the task with the given task ID if it has not yet been started.
Args:
task_id: the task id returned by add_task
Returns:
True if the task was canceled successfully, false otherwise
"""
raise NotImplementedError('TaskRunnerExcpetion: cancel_task')
def __worker(self):
"""Worker fetches tasks one by one from queue & executes them
"""
while not self.stop_flag:
task = self.task_q.get()
task.execute()
print 'Successfully complted task %s' %(task)
self.task_q.task_done()
