import logging
import threading
import heapq
+import itertools
from ganeti import compat
from ganeti import errors
self.priority = priority
+class NoSuchTask(Exception):
+ """Exception raised when a task can't be found.
+
+ """
+
+
class BaseWorker(threading.Thread, object):
"""Base worker class for worker pools.
try:
assert self._HasRunningTaskUnlocked()
- (priority, _, _) = self._current_task
+ (priority, _, _, _) = self._current_task
return priority
finally:
"""
return (self._current_task is not None)
+ def _GetCurrentOrderAndTaskId(self):
+ """Returns the order and task ID of the current task.
+
+ Should only be called from within L{RunTask}.
+
+ """
+ self.pool._lock.acquire()
+ try:
+ assert self._HasRunningTaskUnlocked()
+
+ (_, order_id, task_id, _) = self._current_task
+
+ return (order_id, task_id)
+ finally:
+ self.pool._lock.release()
+
def run(self):
"""Main thread function.
finally:
pool._lock.release()
- (priority, _, args) = self._current_task
+ (priority, _, _, args) = self._current_task
try:
# Run the actual task
assert defer is None
if defer:
assert self._current_task
# Schedule again for later run
- (_, _, args) = self._current_task
- pool._AddTaskUnlocked(args, defer.priority)
+ (_, _, task_id, args) = self._current_task
+ pool._AddTaskUnlocked(args, defer.priority, task_id)
if self._current_task:
self._current_task = None
added to the pool. Due to the nature of threading, they're not
guaranteed to finish in the same order.
+ @type _tasks: list of tuples
+ @ivar _tasks: Each tuple has the format (priority, order ID, task ID,
+ arguments). Priority and order ID are numeric and essentially control the
+ sort order. The order ID is an increasing number denoting the order in
+ which tasks are added to the queue. The task ID is controlled by user of
+ workerpool, see L{AddTask} for details. The task arguments are C{None} for
+ abandoned tasks, otherwise a sequence of arguments to be passed to
+ L{BaseWorker.RunTask}). The list must fulfill the heap property (for use by
+ the C{heapq} module).
+ @type _taskdata: dict; (task IDs as keys, tuples as values)
+ @ivar _taskdata: Mapping from task IDs to entries in L{_tasks}
+
"""
def __init__(self, name, num_workers, worker_class):
"""Constructor for worker pool.
self._termworkers = []
# Queued tasks
- self._counter = 0
+ self._counter = itertools.count()
self._tasks = []
+ self._taskdata = {}
# Start workers
self.Resize(num_workers)
while self._quiescing:
self._pool_to_pool.wait()
- def _AddTaskUnlocked(self, args, priority):
+ def _AddTaskUnlocked(self, args, priority, task_id):
"""Adds a task to the internal queue.
@type args: sequence
@param args: Arguments passed to L{BaseWorker.RunTask}
@type priority: number
@param priority: Task priority
+ @param task_id: Task ID
"""
assert isinstance(args, (tuple, list)), "Arguments must be a sequence"
assert isinstance(priority, (int, long)), "Priority must be numeric"
+ assert task_id is None or isinstance(task_id, (int, long)), \
+ "Task ID must be numeric or None"
+
+ task = [priority, self._counter.next(), task_id, args]
- # This counter is used to ensure elements are processed in their
- # incoming order. For processing they're sorted by priority and then
- # counter.
- self._counter += 1
+ if task_id is not None:
+ assert task_id not in self._taskdata
+ # Keep a reference to change priority later if necessary
+ self._taskdata[task_id] = task
- heapq.heappush(self._tasks, (priority, self._counter, args))
+ # A counter is used to ensure elements are processed in their incoming
+ # order. For processing they're sorted by priority and then counter.
+ heapq.heappush(self._tasks, task)
# Notify a waiting worker
self._pool_to_worker.notify()
- def AddTask(self, args, priority=_DEFAULT_PRIORITY):
+ def AddTask(self, args, priority=_DEFAULT_PRIORITY, task_id=None):
"""Adds a task to the queue.
@type args: sequence
@param args: arguments passed to L{BaseWorker.RunTask}
@type priority: number
@param priority: Task priority
+ @param task_id: Task ID
+ @note: The task ID can be essentially anything that can be used as a
+ dictionary key. Callers, however, must ensure a task ID is unique while a
+ task is in the pool or while it might return to the pool due to deferring
+ using L{DeferTask}.
"""
self._lock.acquire()
try:
self._WaitWhileQuiescingUnlocked()
- self._AddTaskUnlocked(args, priority)
+ self._AddTaskUnlocked(args, priority, task_id)
finally:
self._lock.release()
- def AddManyTasks(self, tasks, priority=_DEFAULT_PRIORITY):
+ def AddManyTasks(self, tasks, priority=_DEFAULT_PRIORITY, task_id=None):
"""Add a list of tasks to the queue.
@type tasks: list of tuples
@type priority: number or list of numbers
@param priority: Priority for all added tasks or a list with the priority
for each task
+ @type task_id: list
+ @param task_id: List with the ID for each task
+ @note: See L{AddTask} for a note on task IDs.
"""
assert compat.all(isinstance(task, (tuple, list)) for task in tasks), \
- "Each task must be a sequence"
-
+ "Each task must be a sequence"
assert (isinstance(priority, (int, long)) or
compat.all(isinstance(prio, (int, long)) for prio in priority)), \
"Priority must be numeric or be a list of numeric values"
+ assert task_id is None or isinstance(task_id, (tuple, list)), \
+ "Task IDs must be in a sequence"
if isinstance(priority, (int, long)):
priority = [priority] * len(tasks)
" number of tasks (%s)" %
(len(priority), len(tasks)))
+ if task_id is None:
+ task_id = [None] * len(tasks)
+ elif len(task_id) != len(tasks):
+ raise errors.ProgrammerError("Number of task IDs (%s) doesn't match"
+ " number of tasks (%s)" %
+ (len(task_id), len(tasks)))
+
self._lock.acquire()
try:
self._WaitWhileQuiescingUnlocked()
assert compat.all(isinstance(prio, (int, long)) for prio in priority)
assert len(tasks) == len(priority)
+ assert len(tasks) == len(task_id)
+
+ for (args, prio, tid) in zip(tasks, priority, task_id):
+ self._AddTaskUnlocked(args, prio, tid)
+ finally:
+ self._lock.release()
- for args, priority in zip(tasks, priority):
- self._AddTaskUnlocked(args, priority)
+ def ChangeTaskPriority(self, task_id, priority):
+ """Changes a task's priority.
+
+ @param task_id: Task ID
+ @type priority: number
+ @param priority: New task priority
+ @raise NoSuchTask: When the task referred by C{task_id} can not be found
+ (it may never have existed, may have already been processed, or is
+ currently running)
+
+ """
+ assert isinstance(priority, (int, long)), "Priority must be numeric"
+
+ self._lock.acquire()
+ try:
+ logging.debug("About to change priority of task %s to %s",
+ task_id, priority)
+
+ # Find old task
+ oldtask = self._taskdata.get(task_id, None)
+ if oldtask is None:
+ msg = "Task '%s' was not found" % task_id
+ logging.debug(msg)
+ raise NoSuchTask(msg)
+
+ # Prepare new task
+ newtask = [priority] + oldtask[1:]
+
+ # Mark old entry as abandoned (this doesn't change the sort order and
+ # therefore doesn't invalidate the heap property of L{self._tasks}).
+ # See also <http://docs.python.org/library/heapq.html#priority-queue-
+ # implementation-notes>.
+ oldtask[-1] = None
+
+ # Change reference to new task entry and forget the old one
+ assert task_id is not None
+ self._taskdata[task_id] = newtask
+
+ # Add a new task with the old number and arguments
+ heapq.heappush(self._tasks, newtask)
+
+ # Notify a waiting worker
+ self._pool_to_worker.notify()
finally:
self._lock.release()
@param worker: Worker thread
"""
- if self._ShouldWorkerTerminateUnlocked(worker):
- return _TERMINATE
+ while True:
+ if self._ShouldWorkerTerminateUnlocked(worker):
+ return _TERMINATE
- # We only wait if there's no task for us.
- if not (self._active and self._tasks):
- logging.debug("Waiting for tasks")
+ # If there's a pending task, return it immediately
+ if self._active and self._tasks:
+ # Get task from queue and tell pool about it
+ try:
+ task = heapq.heappop(self._tasks)
+ finally:
+ self._worker_to_pool.notifyAll()
- while True:
- # wait() releases the lock and sleeps until notified
- self._pool_to_worker.wait()
+ (_, _, task_id, args) = task
- logging.debug("Notified while waiting")
+ # If the priority was changed, "args" is None
+ if args is None:
+ # Try again
+ logging.debug("Found abandoned task (%r)", task)
+ continue
- # Were we woken up in order to terminate?
- if self._ShouldWorkerTerminateUnlocked(worker):
- return _TERMINATE
+ # Delete reference
+ if task_id is not None:
+ del self._taskdata[task_id]
- # Just loop if pool is not processing tasks at this time
- if self._active and self._tasks:
- break
+ return task
- # Get task from queue and tell pool about it
- try:
- return heapq.heappop(self._tasks)
- finally:
- self._worker_to_pool.notifyAll()
+ logging.debug("Waiting for tasks")
+
+ # wait() releases the lock and sleeps until notified
+ self._pool_to_worker.wait()
+
+ logging.debug("Notified while waiting")
def _ShouldWorkerTerminateUnlocked(self, worker):
"""Returns whether a worker should terminate.
return True
return False
+ def HasRunningTasks(self):
+ """Checks whether there's at least one task running.
+
+ """
+ self._lock.acquire()
+ try:
+ return self._HasRunningTasksUnlocked()
+ finally:
+ self._lock.release()
+
def Quiesce(self):
"""Waits until the task queue is empty.
projects / ganeti-local / blobdiff