219 lines
6 KiB
Python
219 lines
6 KiB
Python
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from __future__ import division, print_function, unicode_literals
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import threading
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import abc
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import uuid
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import time
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try:
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import queue
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except ImportError:
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import Queue as queue
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from datetime import datetime
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from collections import namedtuple
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from cps import logger
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log = logger.create()
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# task 'status' consts
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STAT_WAITING = 0
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STAT_FAIL = 1
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STAT_STARTED = 2
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STAT_FINISH_SUCCESS = 3
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# Only retain this many tasks in dequeued list
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TASK_CLEANUP_TRIGGER = 20
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QueuedTask = namedtuple('QueuedTask', 'num, user, added, task')
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def _get_main_thread():
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for t in threading.enumerate():
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if t.__class__.__name__ == '_MainThread':
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return t
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raise Exception("main thread not found?!")
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class ImprovedQueue(queue.Queue):
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def to_list(self):
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"""
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Returns a copy of all items in the queue without removing them.
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"""
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with self.mutex:
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return list(self.queue)
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#Class for all worker tasks in the background
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class WorkerThread(threading.Thread):
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_instance = None
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@classmethod
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def getInstance(cls):
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if cls._instance is None:
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cls._instance = WorkerThread()
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return cls._instance
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def __init__(self):
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threading.Thread.__init__(self)
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self.dequeued = list()
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self.doLock = threading.Lock()
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self.queue = ImprovedQueue()
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self.num = 0
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self.start()
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@classmethod
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def add(cls, user, task):
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ins = cls.getInstance()
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ins.num += 1
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ins.queue.put(QueuedTask(
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num=ins.num,
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user=user,
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added=datetime.now(),
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task=task,
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))
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@property
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def tasks(self):
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with self.doLock:
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tasks = self.queue.to_list() + self.dequeued
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return sorted(tasks, key=lambda x: x.num)
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def cleanup_tasks(self):
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with self.doLock:
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dead = []
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alive = []
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for x in self.dequeued:
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(dead if x.task.dead else alive).append(x)
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# if the ones that we need to keep are within the trigger, do nothing else
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delta = len(self.dequeued) - len(dead)
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if delta > TASK_CLEANUP_TRIGGER:
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ret = alive
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else:
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# otherwise, lop off the oldest dead tasks until we hit the target trigger
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ret = sorted(dead, key=lambda x: x.task.end_time)[-TASK_CLEANUP_TRIGGER:] + alive
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self.dequeued = sorted(ret, key=lambda x: x.num)
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# Main thread loop starting the different tasks
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def run(self):
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main_thread = _get_main_thread()
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while main_thread.is_alive():
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try:
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# this blocks until something is available. This can cause issues when the main thread dies - this
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# thread will remain alive. We implement a timeout to unblock every second which allows us to check if
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# the main thread is still alive.
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# We don't use a daemon here because we don't want the tasks to just be abruptly halted, leading to
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# possible file / database corruption
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item = self.queue.get(timeout=1)
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except queue.Empty:
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time.sleep(1)
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continue
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with self.doLock:
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# add to list so that in-progress tasks show up
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self.dequeued.append(item)
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# once we hit our trigger, start cleaning up dead tasks
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if len(self.dequeued) > TASK_CLEANUP_TRIGGER:
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self.cleanup_tasks()
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# sometimes tasks (like Upload) don't actually have work to do and are created as already finished
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if item.task.stat is STAT_WAITING:
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# CalibreTask.start() should wrap all exceptions in it's own error handling
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item.task.start(self)
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self.queue.task_done()
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class CalibreTask:
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__metaclass__ = abc.ABCMeta
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def __init__(self, message):
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self._progress = 0
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self.stat = STAT_WAITING
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self.error = None
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self.start_time = None
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self.end_time = None
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self.message = message
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self.id = uuid.uuid4()
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@abc.abstractmethod
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def run(self, worker_thread):
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"""Provides the caller some human-readable name for this class"""
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raise NotImplementedError
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@abc.abstractmethod
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def name(self):
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"""Provides the caller some human-readable name for this class"""
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raise NotImplementedError
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def start(self, *args):
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self.start_time = datetime.now()
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self.stat = STAT_STARTED
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# catch any unhandled exceptions in a task and automatically fail it
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try:
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self.run(*args)
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except Exception as ex:
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self._handleError(str(ex))
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log.debug_or_exception(ex)
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self.end_time = datetime.now()
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@property
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def stat(self):
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return self._stat
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@stat.setter
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def stat(self, x):
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self._stat = x
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@property
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def progress(self):
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return self._progress
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@progress.setter
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def progress(self, x):
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if not 0 <= x <= 1:
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raise ValueError("Task progress should within [0, 1] range")
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self._progress = x
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@property
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def error(self):
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return self._error
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@error.setter
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def error(self, x):
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self._error = x
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@property
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def runtime(self):
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return (self.end_time or datetime.now()) - self.start_time
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@property
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def dead(self):
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"""Determines whether or not this task can be garbage collected
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We have a separate dictating this because there may be certain tasks that want to override this
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"""
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# By default, we're good to clean a task if it's "Done"
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return self.stat in (STAT_FINISH_SUCCESS, STAT_FAIL)
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@progress.setter
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def progress(self, x):
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# todo: throw error if outside of [0,1]
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self._progress = x
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def _handleError(self, error_message):
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self.stat = STAT_FAIL
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self.progress = 1
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self.error = error_message
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def _handleSuccess(self):
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self.stat = STAT_FINISH_SUCCESS
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self.progress = 1
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