ganeti.workerpool

57 """Base worker class for worker pools. 58 59 Users of a worker pool must override RunTask in a subclass. 60 61 """ 62 # pylint: disable=W0212

63 - def __init__(self, pool, worker_id):

64 """Constructor for BaseWorker thread. 65 66 @param pool: the parent worker pool 67 @param worker_id: identifier for this worker 68 69 """ 70 super(BaseWorker, self).__init__(name=worker_id) 71 self.pool = pool 72 self._worker_id = worker_id 73 self._current_task = None 74 75 assert self.getName() == worker_id

76

77 - def ShouldTerminate(self):

78 """Returns whether this worker should terminate. 79 80 Should only be called from within L{RunTask}. 81 82 """ 83 self.pool._lock.acquire() 84 try: 85 assert self._HasRunningTaskUnlocked() 86 return self.pool._ShouldWorkerTerminateUnlocked(self) 87 finally: 88 self.pool._lock.release()

89

90 - def GetCurrentPriority(self):

91 """Returns the priority of the current task. 92 93 Should only be called from within L{RunTask}. 94 95 """ 96 self.pool._lock.acquire() 97 try: 98 assert self._HasRunningTaskUnlocked() 99 100 (priority, _, _) = self._current_task 101 102 return priority 103 finally: 104 self.pool._lock.release()

105

106 - def SetTaskName(self, taskname):

107 """Sets the name of the current task. 108 109 Should only be called from within L{RunTask}. 110 111 @type taskname: string 112 @param taskname: Task's name 113 114 """ 115 if taskname: 116 name = "%s/%s" % (self._worker_id, taskname) 117 else: 118 name = self._worker_id 119 120 # Set thread name 121 self.setName(name)

122

123 - def _HasRunningTaskUnlocked(self):

124 """Returns whether this worker is currently running a task. 125 126 """ 127 return (self._current_task is not None)

128

129 - def run(self):

130 """Main thread function. 131 132 Waits for new tasks to show up in the queue. 133 134 """ 135 pool = self.pool 136 137 while True: 138 assert self._current_task is None 139 140 defer = None 141 try: 142 # Wait on lock to be told either to terminate or to do a task 143 pool._lock.acquire() 144 try: 145 task = pool._WaitForTaskUnlocked(self) 146 147 if task is _TERMINATE: 148 # Told to terminate 149 break 150 151 if task is None: 152 # Spurious notification, ignore 153 continue 154 155 self._current_task = task 156 157 # No longer needed, dispose of reference 158 del task 159 160 assert self._HasRunningTaskUnlocked() 161 162 finally: 163 pool._lock.release() 164 165 (priority, _, args) = self._current_task 166 try: 167 # Run the actual task 168 assert defer is None 169 logging.debug("Starting task %r, priority %s", args, priority) 170 assert self.getName() == self._worker_id 171 try: 172 self.RunTask(*args) # pylint: disable=W0142 173 finally: 174 self.SetTaskName(None) 175 logging.debug("Done with task %r, priority %s", args, priority) 176 except DeferTask, err: 177 defer = err 178 179 if defer.priority is None: 180 # Use same priority 181 defer.priority = priority 182 183 logging.debug("Deferring task %r, new priority %s", 184 args, defer.priority) 185 186 assert self._HasRunningTaskUnlocked() 187 except: # pylint: disable=W0702 188 logging.exception("Caught unhandled exception") 189 190 assert self._HasRunningTaskUnlocked() 191 finally: 192 # Notify pool 193 pool._lock.acquire() 194 try: 195 if defer: 196 assert self._current_task 197 # Schedule again for later run 198 (_, _, args) = self._current_task 199 pool._AddTaskUnlocked(args, defer.priority) 200 201 if self._current_task: 202 self._current_task = None 203 pool._worker_to_pool.notifyAll() 204 finally: 205 pool._lock.release() 206 207 assert not self._HasRunningTaskUnlocked() 208 209 logging.debug("Terminates")

210

211 - def RunTask(self, *args):

212 """Function called to start a task. 213 214 This needs to be implemented by child classes. 215 216 """ 217 raise NotImplementedError()

221 """Worker pool with a queue. 222 223 This class is thread-safe. 224 225 Tasks are guaranteed to be started in the order in which they're 226 added to the pool. Due to the nature of threading, they're not 227 guaranteed to finish in the same order. 228 229 """

230 - def __init__(self, name, num_workers, worker_class):

231 """Constructor for worker pool. 232 233 @param num_workers: number of workers to be started 234 (dynamic resizing is not yet implemented) 235 @param worker_class: the class to be instantiated for workers; 236 should derive from L{BaseWorker} 237 238 """ 239 # Some of these variables are accessed by BaseWorker 240 self._lock = threading.Lock() 241 self._pool_to_pool = threading.Condition(self._lock) 242 self._pool_to_worker = threading.Condition(self._lock) 243 self._worker_to_pool = threading.Condition(self._lock) 244 self._worker_class = worker_class 245 self._name = name 246 self._last_worker_id = 0 247 self._workers = [] 248 self._quiescing = False 249 self._active = True 250 251 # Terminating workers 252 self._termworkers = [] 253 254 # Queued tasks 255 self._counter = 0 256 self._tasks = [] 257 258 # Start workers 259 self.Resize(num_workers)

260 261 # TODO: Implement dynamic resizing? 262

263 - def _WaitWhileQuiescingUnlocked(self):

264 """Wait until the worker pool has finished quiescing. 265 266 """ 267 while self._quiescing: 268 self._pool_to_pool.wait()

269

270 - def _AddTaskUnlocked(self, args, priority):

271 """Adds a task to the internal queue. 272 273 @type args: sequence 274 @param args: Arguments passed to L{BaseWorker.RunTask} 275 @type priority: number 276 @param priority: Task priority 277 278 """ 279 assert isinstance(args, (tuple, list)), "Arguments must be a sequence" 280 assert isinstance(priority, (int, long)), "Priority must be numeric" 281 282 # This counter is used to ensure elements are processed in their 283 # incoming order. For processing they're sorted by priority and then 284 # counter. 285 self._counter += 1 286 287 heapq.heappush(self._tasks, (priority, self._counter, args)) 288 289 # Notify a waiting worker 290 self._pool_to_worker.notify()

291

292 - def AddTask(self, args, priority=_DEFAULT_PRIORITY):

293 """Adds a task to the queue. 294 295 @type args: sequence 296 @param args: arguments passed to L{BaseWorker.RunTask} 297 @type priority: number 298 @param priority: Task priority 299 300 """ 301 self._lock.acquire() 302 try: 303 self._WaitWhileQuiescingUnlocked() 304 self._AddTaskUnlocked(args, priority) 305 finally: 306 self._lock.release()

307

308 - def AddManyTasks(self, tasks, priority=_DEFAULT_PRIORITY):

309 """Add a list of tasks to the queue. 310 311 @type tasks: list of tuples 312 @param tasks: list of args passed to L{BaseWorker.RunTask} 313 @type priority: number or list of numbers 314 @param priority: Priority for all added tasks or a list with the priority 315 for each task 316 317 """ 318 assert compat.all(isinstance(task, (tuple, list)) for task in tasks), \ 319 "Each task must be a sequence" 320 321 assert (isinstance(priority, (int, long)) or 322 compat.all(isinstance(prio, (int, long)) for prio in priority)), \ 323 "Priority must be numeric or be a list of numeric values" 324 325 if isinstance(priority, (int, long)): 326 priority = [priority] * len(tasks) 327 elif len(priority) != len(tasks): 328 raise errors.ProgrammerError("Number of priorities (%s) doesn't match" 329 " number of tasks (%s)" % 330 (len(priority), len(tasks))) 331 332 self._lock.acquire() 333 try: 334 self._WaitWhileQuiescingUnlocked() 335 336 assert compat.all(isinstance(prio, (int, long)) for prio in priority) 337 assert len(tasks) == len(priority) 338 339 for args, priority in zip(tasks, priority): 340 self._AddTaskUnlocked(args, priority) 341 finally: 342 self._lock.release()

343

344 - def SetActive(self, active):

345 """Enable/disable processing of tasks. 346 347 This is different from L{Quiesce} in the sense that this function just 348 changes an internal flag and doesn't wait for the queue to be empty. Tasks 349 already being processed continue normally, but no new tasks will be 350 started. New tasks can still be added. 351 352 @type active: bool 353 @param active: Whether tasks should be processed 354 355 """ 356 self._lock.acquire() 357 try: 358 self._active = active 359 360 if active: 361 # Tell all workers to continue processing 362 self._pool_to_worker.notifyAll() 363 finally: 364 self._lock.release()

365

366 - def _WaitForTaskUnlocked(self, worker):

367 """Waits for a task for a worker. 368 369 @type worker: L{BaseWorker} 370 @param worker: Worker thread 371 372 """ 373 if self._ShouldWorkerTerminateUnlocked(worker): 374 return _TERMINATE 375 376 # We only wait if there's no task for us. 377 if not (self._active and self._tasks): 378 logging.debug("Waiting for tasks") 379 380 while True: 381 # wait() releases the lock and sleeps until notified 382 self._pool_to_worker.wait() 383 384 logging.debug("Notified while waiting") 385 386 # Were we woken up in order to terminate? 387 if self._ShouldWorkerTerminateUnlocked(worker): 388 return _TERMINATE 389 390 # Just loop if pool is not processing tasks at this time 391 if self._active and self._tasks: 392 break 393 394 # Get task from queue and tell pool about it 395 try: 396 return heapq.heappop(self._tasks) 397 finally: 398 self._worker_to_pool.notifyAll()

399

400 - def _ShouldWorkerTerminateUnlocked(self, worker):

401 """Returns whether a worker should terminate. 402 403 """ 404 return (worker in self._termworkers)

405

406 - def _HasRunningTasksUnlocked(self):

407 """Checks whether there's a task running in a worker. 408 409 """ 410 for worker in self._workers + self._termworkers: 411 if worker._HasRunningTaskUnlocked(): # pylint: disable=W0212 412 return True 413 return False

414

415 - def HasRunningTasks(self):

416 """Checks whether there's at least one task running. 417 418 """ 419 self._lock.acquire() 420 try: 421 return self._HasRunningTasksUnlocked() 422 finally: 423 self._lock.release()

424

425 - def Quiesce(self):

426 """Waits until the task queue is empty. 427 428 """ 429 self._lock.acquire() 430 try: 431 self._quiescing = True 432 433 # Wait while there are tasks pending or running 434 while self._tasks or self._HasRunningTasksUnlocked(): 435 self._worker_to_pool.wait() 436 437 finally: 438 self._quiescing = False 439 440 # Make sure AddTasks continues in case it was waiting 441 self._pool_to_pool.notifyAll() 442 443 self._lock.release()

444

445 - def _NewWorkerIdUnlocked(self):

446 """Return an identifier for a new worker. 447 448 """ 449 self._last_worker_id += 1 450 451 return "%s%d" % (self._name, self._last_worker_id)

452

453 - def _ResizeUnlocked(self, num_workers):

454 """Changes the number of workers. 455 456 """ 457 assert num_workers >= 0, "num_workers must be >= 0" 458 459 logging.debug("Resizing to %s workers", num_workers) 460 461 current_count = len(self._workers) 462 463 if current_count == num_workers: 464 # Nothing to do 465 pass 466 467 elif current_count > num_workers: 468 if num_workers == 0: 469 # Create copy of list to iterate over while lock isn't held. 470 termworkers = self._workers[:] 471 del self._workers[:] 472 else: 473 # TODO: Implement partial downsizing 474 raise NotImplementedError() 475 #termworkers = ... 476 477 self._termworkers += termworkers 478 479 # Notify workers that something has changed 480 self._pool_to_worker.notifyAll() 481 482 # Join all terminating workers 483 self._lock.release() 484 try: 485 for worker in termworkers: 486 logging.debug("Waiting for thread %s", worker.getName()) 487 worker.join() 488 finally: 489 self._lock.acquire() 490 491 # Remove terminated threads. This could be done in a more efficient way 492 # (del self._termworkers[:]), but checking worker.isAlive() makes sure we 493 # don't leave zombie threads around. 494 for worker in termworkers: 495 assert worker in self._termworkers, ("Worker not in list of" 496 " terminating workers") 497 if not worker.isAlive(): 498 self._termworkers.remove(worker) 499 500 assert not self._termworkers, "Zombie worker detected" 501 502 elif current_count < num_workers: 503 # Create (num_workers - current_count) new workers 504 for _ in range(num_workers - current_count): 505 worker = self._worker_class(self, self._NewWorkerIdUnlocked()) 506 self._workers.append(worker) 507 worker.start()

508

509 - def Resize(self, num_workers):

510 """Changes the number of workers in the pool. 511 512 @param num_workers: the new number of workers 513 514 """ 515 self._lock.acquire() 516 try: 517 return self._ResizeUnlocked(num_workers) 518 finally: 519 self._lock.release()

520

521 - def TerminateWorkers(self):

522 """Terminate all worker threads. 523 524 Unstarted tasks will be ignored. 525 526 """ 527 logging.debug("Terminating all workers") 528 529 self._lock.acquire() 530 try: 531 self._ResizeUnlocked(0) 532 533 if self._tasks: 534 logging.debug("There are %s tasks left", len(self._tasks)) 535 finally: 536 self._lock.release() 537 538 logging.debug("All workers terminated")

Source Code for Module ganeti.workerpool