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Diffstat (limited to 'taskthread/__init__.py')
| -rw-r--r-- | taskthread/__init__.py | 296 |
1 files changed, 296 insertions, 0 deletions
diff --git a/taskthread/__init__.py b/taskthread/__init__.py new file mode 100644 index 0000000..a734a82 --- /dev/null +++ b/taskthread/__init__.py @@ -0,0 +1,296 @@ +# Copyright 2013 Hewlett-Packard Development Company, L.P. +# +# Licensed under the Apache License, Version 2.0 (the "License"); you may +# not use this file except in compliance with the License. You may obtain +# a copy of the License at +# +# http://www.apache.org/licenses/LICENSE-2.0 +# +# Unless required by applicable law or agreed to in writing, software +# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT +# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the +# License for the specific language governing permissions and limitations +# under the License. +import logging +import threading + +__version__ = '1.4' + + +logger = logging.getLogger(__name__) + + +class TaskInProcessException(BaseException): + pass + + +class TaskThread(threading.Thread): + """ + A thread object that repeats a task. + + Usage example:: + + from taskthread import TaskThread + + import time + + def my_task(*args, **kwargs): + print args, kwargs + + task_thread = TaskThread(my_task) + task_thread.start() + for i in xrange(10): + task_thread.run_task() + task_thread.join_task() + task_thread.join() + + .. note:: If :py:meth:`~TaskThread.run_task` is + invoked while run_task is in progress, + :py:class:`~.TaskInProcessException` will + be raised. + + :param task: + A ``function``. This param is the task to execute when + run_task is called. + :param event: + A ``threading.Event``. This event will be set when run_task + is called. The default value is a new event, but may be + specified for testing purposes. + """ + + daemon = True + ''' + Threads marked as daemon will be terminated. + ''' + def __init__(self, task, event=threading.Event(), + *args, **kwargs): + super(TaskThread, self).__init__() + self.task = task + self.task_event = event + self.running = True + self.running_lock = threading.Lock() + self.in_task = False + self.task_complete = threading.Event() + self.args = args + self.kwargs = kwargs + + def run(self): + """ + Called by threading.Thread, this runs in the new thread. + """ + while True: + self.task_event.wait() + if not self.running: + logger.debug("TaskThread exiting") + return + logger.debug("TaskThread starting task") + with self.running_lock: + self.task_event.clear() + self.task_complete.clear() + self.task(*self.args, **self.kwargs) + with self.running_lock: + self.in_task = False + self.task_complete.set() + + def run_task(self, *args, **kwargs): + """ + Run an instance of the task. + + :param args: + The arguments to pass to the task. + + :param kwargs: + The keyword arguments to pass to the task. + """ + # Don't allow this call if the thread is currently + # in a task. + with self.running_lock: + if self.in_task: + raise TaskInProcessException() + self.in_task = True + logger.debug("Waking up the thread") + self.args = args + self.kwargs = kwargs + # Wake up the thread to do it's thing + self.task_event.set() + + def join_task(self, time_out): + """ + Wait for the currently running task to complete. + + :param time_out: + An ``int``. The amount of time to wait for the + task to finish. + """ + with self.running_lock: + if not self.in_task: + return + + success = self.task_complete.wait(time_out) + if success: + self.task_complete.clear() + return success + + def join(self, timeout=None): + """ + Wait for the task to finish + """ + self.running = False + self.task_event.set() + super(TaskThread, self).join(timeout=timeout) + + +class TimerTask(object): + """ + An object that executes a commit function at a given interval. + This class is driven by a TaskThread. A new TaskThread will be + created the first time :py:meth:`.~start` is called. All + subsequent calls to start will reuse the same thread. + + Usage example:: + + from taskthread import TimerTask + import time + + count = 0 + def get_count(): + return count + def execute(): + print "Count: %d" % count + + task = TimerTask(execute, + timeout=10, + count_fcn=get_count, + threshold=1) + + task.start() + + for i in xrange(100000): + count += 1 + time.sleep(1) + task.stop() + count = 0 + task.start() + for i in xrange(100000): + count += 1 + time.sleep(1) + task.shutdown() + + :param execute_fcn: + A `function`. This function will be executed on each time interval. + + :param delay: + An `int`. The delay in **seconds** invocations of + `execute_fcn`. Default: `10`. + + :param count_fcn: + A `function`. This function returns a current count. If the count + has not changed more the `threshold` since the last invocation of + `execute_fcn`, `execute_fcn` will not be called again. If not + specified, `execute_fcn` will be called each time the timer fires. + **Optional**. If count_fcn is specified, ``threshold`` is required. + + :param threshold: + An `int`. Specifies the minimum delta in `count_fcn` that must be + met for `execute_fcn` to be invoked. **Optional**. Must be + specified in conjunction with `count_fcn`. + + """ + def __init__(self, execute_fcn, delay=10, count_fcn=None, threshold=None): + self.running = True + self.execute_fcn = execute_fcn + self.last_count = 0 + self.event = threading.Event() + self.delay = delay + self.thread = None + self.running_lock = threading.RLock() + if bool(threshold) != bool(count_fcn): + raise ValueError("Must specify threshold " + "and count_fcn, or neither") + + self.count_fcn = count_fcn + self.threshold = threshold + + def start(self): + """ + Start the task. This starts a :py:class:`.~TaskThread`, and starts + running run_threshold_timer on the thread. + + """ + if not self.thread: + logger.debug('Starting up the taskthread') + self.thread = TaskThread(self._run_threshold_timer) + self.thread.start() + + if self.threshold: + self.last_count = 0 + + logger.debug('Running the task') + self.running = True + self.thread.run_task() + + def stop(self): + """ + Stop the task, leaving the :py:class:`.~TaskThread` running + so start can be called again. + + """ + logger.debug('Stopping the task') + wait = False + with self.running_lock: + if self.running: + wait = True + self.running = False + if wait: + self.event.set() + self.thread.join_task(2) + + def shutdown(self): + """ + Close down the task thread and stop the task if it is running. + + """ + logger.debug('Shutting down the task') + self.stop() + self.thread.join(2) + + def _exec_if_threshold_met(self): + new_count = self.count_fcn() + logger.debug('new_count: %d' % new_count) + if new_count >= self.last_count + self.threshold: + self.execute_fcn() + self.last_count = new_count + + def _exec(self): + if self.count_fcn: + self._exec_if_threshold_met() + else: + self.execute_fcn() + + def _wait(self): + self.event.wait(timeout=self.delay) + self.event.clear() + logger.debug('Task woken up') + + def _exit_loop(self): + """ + If self.running is false, it means the task should shut down. + """ + exit_loop = False + with self.running_lock: + if not self.running: + exit_loop = True + logger.debug('Task shutting down') + return exit_loop + + def _run_threshold_timer(self): + """ + Main loop of the timer task + + """ + logger.debug('In Task') + while True: + self._wait() + if self._exit_loop(): + return + self._exec() |