ganeti.locking

1 # 2 # 3 4 # Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Google Inc. 5 # 6 # This program is free software; you can redistribute it and/or modify 7 # it under the terms of the GNU General Public License as published by 8 # the Free Software Foundation; either version 2 of the License, or 9 # (at your option) any later version. 10 # 11 # This program is distributed in the hope that it will be useful, but 12 # WITHOUT ANY WARRANTY; without even the implied warranty of 13 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14 # General Public License for more details. 15 # 16 # You should have received a copy of the GNU General Public License 17 # along with this program; if not, write to the Free Software 18 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 19 # 02110-1301, USA. 20 21 """Module implementing the Ganeti locking code.""" 22 23 # pylint: disable=W0212 24 25 # W0212 since e.g. LockSet methods use (a lot) the internals of 26 # SharedLock 27 28 import os 29 import select 30 import threading 31 import errno 32 import weakref 33 import logging 34 import heapq 35 import itertools 36 import time 37 38 from ganeti import errors 39 from ganeti import utils 40 from ganeti import compat 41 from ganeti import query 42 43 44 _EXCLUSIVE_TEXT = "exclusive" 45 _SHARED_TEXT = "shared" 46 _DELETED_TEXT = "deleted" 47 48 _DEFAULT_PRIORITY = 0

49 50 51 -def ssynchronized(mylock, shared=0):

52 """Shared Synchronization decorator. 53 54 Calls the function holding the given lock, either in exclusive or shared 55 mode. It requires the passed lock to be a SharedLock (or support its 56 semantics). 57 58 @type mylock: lockable object or string 59 @param mylock: lock to acquire or class member name of the lock to acquire 60 61 """ 62 def wrap(fn): 63 def sync_function(*args, **kwargs): 64 if isinstance(mylock, basestring): 65 assert args, "cannot ssynchronize on non-class method: self not found" 66 # args[0] is "self" 67 lock = getattr(args[0], mylock) 68 else: 69 lock = mylock 70 lock.acquire(shared=shared) 71 try: 72 return fn(*args, **kwargs) 73 finally: 74 lock.release()

75 return sync_function 76 return wrap 77

78 79 -class _SingleNotifyPipeConditionWaiter(object):

80 """Helper class for SingleNotifyPipeCondition 81 82 """ 83 __slots__ = [ 84 "_fd", 85 "_poller", 86 ] 87

88 - def __init__(self, poller, fd):

89 """Constructor for _SingleNotifyPipeConditionWaiter 90 91 @type poller: select.poll 92 @param poller: Poller object 93 @type fd: int 94 @param fd: File descriptor to wait for 95 96 """ 97 object.__init__(self) 98 self._poller = poller 99 self._fd = fd

100

101 - def __call__(self, timeout):

102 """Wait for something to happen on the pipe. 103 104 @type timeout: float or None 105 @param timeout: Timeout for waiting (can be None) 106 107 """ 108 running_timeout = utils.RunningTimeout(timeout, True) 109 110 while True: 111 remaining_time = running_timeout.Remaining() 112 113 if remaining_time is not None: 114 if remaining_time < 0.0: 115 break 116 117 # Our calculation uses seconds, poll() wants milliseconds 118 remaining_time *= 1000 119 120 try: 121 result = self._poller.poll(remaining_time) 122 except EnvironmentError, err: 123 if err.errno != errno.EINTR: 124 raise 125 result = None 126 127 # Check whether we were notified 128 if result and result[0][0] == self._fd: 129 break

130

131 132 -class _BaseCondition(object):

133 """Base class containing common code for conditions. 134 135 Some of this code is taken from python's threading module. 136 137 """ 138 __slots__ = [ 139 "_lock", 140 "acquire", 141 "release", 142 "_is_owned", 143 "_acquire_restore", 144 "_release_save", 145 ] 146

147 - def __init__(self, lock):

148 """Constructor for _BaseCondition. 149 150 @type lock: threading.Lock 151 @param lock: condition base lock 152 153 """ 154 object.__init__(self) 155 156 try: 157 self._release_save = lock._release_save 158 except AttributeError: 159 self._release_save = self._base_release_save 160 try: 161 self._acquire_restore = lock._acquire_restore 162 except AttributeError: 163 self._acquire_restore = self._base_acquire_restore 164 try: 165 self._is_owned = lock.is_owned 166 except AttributeError: 167 self._is_owned = self._base_is_owned 168 169 self._lock = lock 170 171 # Export the lock's acquire() and release() methods 172 self.acquire = lock.acquire 173 self.release = lock.release

174

175 - def _base_is_owned(self):

176 """Check whether lock is owned by current thread. 177 178 """ 179 if self._lock.acquire(0): 180 self._lock.release() 181 return False 182 return True

183

184 - def _base_release_save(self):

185 self._lock.release()

186

187 - def _base_acquire_restore(self, _):

188 self._lock.acquire()

189

190 - def _check_owned(self):

191 """Raise an exception if the current thread doesn't own the lock. 192 193 """ 194 if not self._is_owned(): 195 raise RuntimeError("cannot work with un-aquired lock")

196

197 198 -class SingleNotifyPipeCondition(_BaseCondition):

199 """Condition which can only be notified once. 200 201 This condition class uses pipes and poll, internally, to be able to wait for 202 notification with a timeout, without resorting to polling. It is almost 203 compatible with Python's threading.Condition, with the following differences: 204 - notifyAll can only be called once, and no wait can happen after that 205 - notify is not supported, only notifyAll 206 207 """ 208 209 __slots__ = [ 210 "_poller", 211 "_read_fd", 212 "_write_fd", 213 "_nwaiters", 214 "_notified", 215 ] 216 217 _waiter_class = _SingleNotifyPipeConditionWaiter 218

219 - def __init__(self, lock):

220 """Constructor for SingleNotifyPipeCondition 221 222 """ 223 _BaseCondition.__init__(self, lock) 224 self._nwaiters = 0 225 self._notified = False 226 self._read_fd = None 227 self._write_fd = None 228 self._poller = None

229

230 - def _check_unnotified(self):

231 """Throws an exception if already notified. 232 233 """ 234 if self._notified: 235 raise RuntimeError("cannot use already notified condition")

236

237 - def _Cleanup(self):

238 """Cleanup open file descriptors, if any. 239 240 """ 241 if self._read_fd is not None: 242 os.close(self._read_fd) 243 self._read_fd = None 244 245 if self._write_fd is not None: 246 os.close(self._write_fd) 247 self._write_fd = None 248 self._poller = None

249

250 - def wait(self, timeout):

251 """Wait for a notification. 252 253 @type timeout: float or None 254 @param timeout: Waiting timeout (can be None) 255 256 """ 257 self._check_owned() 258 self._check_unnotified() 259 260 self._nwaiters += 1 261 try: 262 if self._poller is None: 263 (self._read_fd, self._write_fd) = os.pipe() 264 self._poller = select.poll() 265 self._poller.register(self._read_fd, select.POLLHUP) 266 267 wait_fn = self._waiter_class(self._poller, self._read_fd) 268 state = self._release_save() 269 try: 270 # Wait for notification 271 wait_fn(timeout) 272 finally: 273 # Re-acquire lock 274 self._acquire_restore(state) 275 finally: 276 self._nwaiters -= 1 277 if self._nwaiters == 0: 278 self._Cleanup()

279

280 - def notifyAll(self): # pylint: disable=C0103

281 """Close the writing side of the pipe to notify all waiters. 282 283 """ 284 self._check_owned() 285 self._check_unnotified() 286 self._notified = True 287 if self._write_fd is not None: 288 os.close(self._write_fd) 289 self._write_fd = None

290

291 292 -class PipeCondition(_BaseCondition):

293 """Group-only non-polling condition with counters. 294 295 This condition class uses pipes and poll, internally, to be able to wait for 296 notification with a timeout, without resorting to polling. It is almost 297 compatible with Python's threading.Condition, but only supports notifyAll and 298 non-recursive locks. As an additional features it's able to report whether 299 there are any waiting threads. 300 301 """ 302 __slots__ = [ 303 "_waiters", 304 "_single_condition", 305 ] 306 307 _single_condition_class = SingleNotifyPipeCondition 308

309 - def __init__(self, lock):

310 """Initializes this class. 311 312 """ 313 _BaseCondition.__init__(self, lock) 314 self._waiters = set() 315 self._single_condition = self._single_condition_class(self._lock)

316

317 - def wait(self, timeout):

318 """Wait for a notification. 319 320 @type timeout: float or None 321 @param timeout: Waiting timeout (can be None) 322 323 """ 324 self._check_owned() 325 326 # Keep local reference to the pipe. It could be replaced by another thread 327 # notifying while we're waiting. 328 cond = self._single_condition 329 330 self._waiters.add(threading.currentThread()) 331 try: 332 cond.wait(timeout) 333 finally: 334 self._check_owned() 335 self._waiters.remove(threading.currentThread())

336

337 - def notifyAll(self): # pylint: disable=C0103

338 """Notify all currently waiting threads. 339 340 """ 341 self._check_owned() 342 self._single_condition.notifyAll() 343 self._single_condition = self._single_condition_class(self._lock)

344

345 - def get_waiting(self):

346 """Returns a list of all waiting threads. 347 348 """ 349 self._check_owned() 350 351 return self._waiters

352

353 - def has_waiting(self):

354 """Returns whether there are active waiters. 355 356 """ 357 self._check_owned() 358 359 return bool(self._waiters)

360

361 - def __repr__(self):

362 return ("<%s.%s waiters=%s at %#x>" % 363 (self.__class__.__module__, self.__class__.__name__, 364 self._waiters, id(self)))

365

366 367 -class _PipeConditionWithMode(PipeCondition):

368 __slots__ = [ 369 "shared", 370 ] 371

372 - def __init__(self, lock, shared):

373 """Initializes this class. 374 375 """ 376 self.shared = shared 377 PipeCondition.__init__(self, lock)

378

379 380 -class SharedLock(object):

381 """Implements a shared lock. 382 383 Multiple threads can acquire the lock in a shared way by calling 384 C{acquire(shared=1)}. In order to acquire the lock in an exclusive way 385 threads can call C{acquire(shared=0)}. 386 387 Notes on data structures: C{__pending} contains a priority queue (heapq) of 388 all pending acquires: C{[(priority1: prioqueue1), (priority2: prioqueue2), 389 ...]}. Each per-priority queue contains a normal in-order list of conditions 390 to be notified when the lock can be acquired. Shared locks are grouped 391 together by priority and the condition for them is stored in 392 C{__pending_shared} if it already exists. C{__pending_by_prio} keeps 393 references for the per-priority queues indexed by priority for faster access. 394 395 @type name: string 396 @ivar name: the name of the lock 397 398 """ 399 __slots__ = [ 400 "__weakref__", 401 "__deleted", 402 "__exc", 403 "__lock", 404 "__pending", 405 "__pending_by_prio", 406 "__pending_shared", 407 "__shr", 408 "__time_fn", 409 "name", 410 ] 411 412 __condition_class = _PipeConditionWithMode 413

414 - def __init__(self, name, monitor=None, _time_fn=time.time):

415 """Construct a new SharedLock. 416 417 @param name: the name of the lock 418 @type monitor: L{LockMonitor} 419 @param monitor: Lock monitor with which to register 420 421 """ 422 object.__init__(self) 423 424 self.name = name 425 426 # Used for unittesting 427 self.__time_fn = _time_fn 428 429 # Internal lock 430 self.__lock = threading.Lock() 431 432 # Queue containing waiting acquires 433 self.__pending = [] 434 self.__pending_by_prio = {} 435 self.__pending_shared = {} 436 437 # Current lock holders 438 self.__shr = set() 439 self.__exc = None 440 441 # is this lock in the deleted state? 442 self.__deleted = False 443 444 # Register with lock monitor 445 if monitor: 446 logging.debug("Adding lock %s to monitor", name) 447 monitor.RegisterLock(self)

448

449 - def __repr__(self):

450 return ("<%s.%s name=%s at %#x>" % 451 (self.__class__.__module__, self.__class__.__name__, 452 self.name, id(self)))

453

454 - def GetLockInfo(self, requested):

455 """Retrieves information for querying locks. 456 457 @type requested: set 458 @param requested: Requested information, see C{query.LQ_*} 459 460 """ 461 self.__lock.acquire() 462 try: 463 # Note: to avoid unintentional race conditions, no references to 464 # modifiable objects should be returned unless they were created in this 465 # function. 466 mode = None 467 owner_names = None 468 469 if query.LQ_MODE in requested: 470 if self.__deleted: 471 mode = _DELETED_TEXT 472 assert not (self.__exc or self.__shr) 473 elif self.__exc: 474 mode = _EXCLUSIVE_TEXT 475 elif self.__shr: 476 mode = _SHARED_TEXT 477 478 # Current owner(s) are wanted 479 if query.LQ_OWNER in requested: 480 if self.__exc: 481 owner = [self.__exc] 482 else: 483 owner = self.__shr 484 485 if owner: 486 assert not self.__deleted 487 owner_names = [i.getName() for i in owner] 488 489 # Pending acquires are wanted 490 if query.LQ_PENDING in requested: 491 pending = [] 492 493 # Sorting instead of copying and using heaq functions for simplicity 494 for (_, prioqueue) in sorted(self.__pending): 495 for cond in prioqueue: 496 if cond.shared: 497 pendmode = _SHARED_TEXT 498 else: 499 pendmode = _EXCLUSIVE_TEXT 500 501 # List of names will be sorted in L{query._GetLockPending} 502 pending.append((pendmode, [i.getName() 503 for i in cond.get_waiting()])) 504 else: 505 pending = None 506 507 return [(self.name, mode, owner_names, pending)] 508 finally: 509 self.__lock.release()

510

511 - def __check_deleted(self):

512 """Raises an exception if the lock has been deleted. 513 514 """ 515 if self.__deleted: 516 raise errors.LockError("Deleted lock %s" % self.name)

517

518 - def __is_sharer(self):

519 """Is the current thread sharing the lock at this time? 520 521 """ 522 return threading.currentThread() in self.__shr

523

524 - def __is_exclusive(self):

525 """Is the current thread holding the lock exclusively at this time? 526 527 """ 528 return threading.currentThread() == self.__exc

529

530 - def __is_owned(self, shared=-1):

531 """Is the current thread somehow owning the lock at this time? 532 533 This is a private version of the function, which presumes you're holding 534 the internal lock. 535 536 """ 537 if shared < 0: 538 return self.__is_sharer() or self.__is_exclusive() 539 elif shared: 540 return self.__is_sharer() 541 else: 542 return self.__is_exclusive()

543

544 - def is_owned(self, shared=-1):

545 """Is the current thread somehow owning the lock at this time? 546 547 @param shared: 548 - < 0: check for any type of ownership (default) 549 - 0: check for exclusive ownership 550 - > 0: check for shared ownership 551 552 """ 553 self.__lock.acquire() 554 try: 555 return self.__is_owned(shared=shared) 556 finally: 557 self.__lock.release()

558 559 #: Necessary to remain compatible with threading.Condition, which tries to 560 #: retrieve a locks' "_is_owned" attribute 561 _is_owned = is_owned 562

563 - def _count_pending(self):

564 """Returns the number of pending acquires. 565 566 @rtype: int 567 568 """ 569 self.__lock.acquire() 570 try: 571 return sum(len(prioqueue) for (_, prioqueue) in self.__pending) 572 finally: 573 self.__lock.release()

574

575 - def _check_empty(self):

576 """Checks whether there are any pending acquires. 577 578 @rtype: bool 579 580 """ 581 self.__lock.acquire() 582 try: 583 # Order is important: __find_first_pending_queue modifies __pending 584 (_, prioqueue) = self.__find_first_pending_queue() 585 586 return not (prioqueue or 587 self.__pending or 588 self.__pending_by_prio or 589 self.__pending_shared) 590 finally: 591 self.__lock.release()

592

593 - def __do_acquire(self, shared):

594 """Actually acquire the lock. 595 596 """ 597 if shared: 598 self.__shr.add(threading.currentThread()) 599 else: 600 self.__exc = threading.currentThread()

601

602 - def __can_acquire(self, shared):

603 """Determine whether lock can be acquired. 604 605 """ 606 if shared: 607 return self.__exc is None 608 else: 609 return len(self.__shr) == 0 and self.__exc is None

610

611 - def __find_first_pending_queue(self):

612 """Tries to find the topmost queued entry with pending acquires. 613 614 Removes empty entries while going through the list. 615 616 """ 617 while self.__pending: 618 (priority, prioqueue) = self.__pending[0] 619 620 if prioqueue: 621 return (priority, prioqueue) 622 623 # Remove empty queue 624 heapq.heappop(self.__pending) 625 del self.__pending_by_prio[priority] 626 assert priority not in self.__pending_shared 627 628 return (None, None)

629

630 - def __is_on_top(self, cond):

631 """Checks whether the passed condition is on top of the queue. 632 633 The caller must make sure the queue isn't empty. 634 635 """ 636 (_, prioqueue) = self.__find_first_pending_queue() 637 638 return cond == prioqueue[0]

639

640 - def __acquire_unlocked(self, shared, timeout, priority):

641 """Acquire a shared lock. 642 643 @param shared: whether to acquire in shared mode; by default an 644 exclusive lock will be acquired 645 @param timeout: maximum waiting time before giving up 646 @type priority: integer 647 @param priority: Priority for acquiring lock 648 649 """ 650 self.__check_deleted() 651 652 # We cannot acquire the lock if we already have it 653 assert not self.__is_owned(), ("double acquire() on a non-recursive lock" 654 " %s" % self.name) 655 656 # Remove empty entries from queue 657 self.__find_first_pending_queue() 658 659 # Check whether someone else holds the lock or there are pending acquires. 660 if not self.__pending and self.__can_acquire(shared): 661 # Apparently not, can acquire lock directly. 662 self.__do_acquire(shared) 663 return True 664 665 prioqueue = self.__pending_by_prio.get(priority, None) 666 667 if shared: 668 # Try to re-use condition for shared acquire 669 wait_condition = self.__pending_shared.get(priority, None) 670 assert (wait_condition is None or 671 (wait_condition.shared and wait_condition in prioqueue)) 672 else: 673 wait_condition = None 674 675 if wait_condition is None: 676 if prioqueue is None: 677 assert priority not in self.__pending_by_prio 678 679 prioqueue = [] 680 heapq.heappush(self.__pending, (priority, prioqueue)) 681 self.__pending_by_prio[priority] = prioqueue 682 683 wait_condition = self.__condition_class(self.__lock, shared) 684 prioqueue.append(wait_condition) 685 686 if shared: 687 # Keep reference for further shared acquires on same priority. This is 688 # better than trying to find it in the list of pending acquires. 689 assert priority not in self.__pending_shared 690 self.__pending_shared[priority] = wait_condition 691 692 wait_start = self.__time_fn() 693 acquired = False 694 695 try: 696 # Wait until we become the topmost acquire in the queue or the timeout 697 # expires. 698 while True: 699 if self.__is_on_top(wait_condition) and self.__can_acquire(shared): 700 self.__do_acquire(shared) 701 acquired = True 702 break 703 704 # A lot of code assumes blocking acquires always succeed, therefore we 705 # can never return False for a blocking acquire 706 if (timeout is not None and 707 utils.TimeoutExpired(wait_start, timeout, _time_fn=self.__time_fn)): 708 break 709 710 # Wait for notification 711 wait_condition.wait(timeout) 712 self.__check_deleted() 713 finally: 714 # Remove condition from queue if there are no more waiters 715 if not wait_condition.has_waiting(): 716 prioqueue.remove(wait_condition) 717 if wait_condition.shared: 718 # Remove from list of shared acquires if it wasn't while releasing 719 # (e.g. on lock deletion) 720 self.__pending_shared.pop(priority, None) 721 722 return acquired

723

724 - def acquire(self, shared=0, timeout=None, priority=None, 725 test_notify=None):

726 """Acquire a shared lock. 727 728 @type shared: integer (0/1) used as a boolean 729 @param shared: whether to acquire in shared mode; by default an 730 exclusive lock will be acquired 731 @type timeout: float 732 @param timeout: maximum waiting time before giving up 733 @type priority: integer 734 @param priority: Priority for acquiring lock 735 @type test_notify: callable or None 736 @param test_notify: Special callback function for unittesting 737 738 """ 739 if priority is None: 740 priority = _DEFAULT_PRIORITY 741 742 self.__lock.acquire() 743 try: 744 # We already got the lock, notify now 745 if __debug__ and callable(test_notify): 746 test_notify() 747 748 return self.__acquire_unlocked(shared, timeout, priority) 749 finally: 750 self.__lock.release()

751

752 - def downgrade(self):

753 """Changes the lock mode from exclusive to shared. 754 755 Pending acquires in shared mode on the same priority will go ahead. 756 757 """ 758 self.__lock.acquire() 759 try: 760 assert self.__is_owned(), "Lock must be owned" 761 762 if self.__is_exclusive(): 763 # Do nothing if the lock is already acquired in shared mode 764 self.__exc = None 765 self.__do_acquire(1) 766 767 # Important: pending shared acquires should only jump ahead if there 768 # was a transition from exclusive to shared, otherwise an owner of a 769 # shared lock can keep calling this function to push incoming shared 770 # acquires 771 (priority, prioqueue) = self.__find_first_pending_queue() 772 if prioqueue: 773 # Is there a pending shared acquire on this priority? 774 cond = self.__pending_shared.pop(priority, None) 775 if cond: 776 assert cond.shared 777 assert cond in prioqueue 778 779 # Ensure shared acquire is on top of queue 780 if len(prioqueue) > 1: 781 prioqueue.remove(cond) 782 prioqueue.insert(0, cond) 783 784 # Notify 785 cond.notifyAll() 786 787 assert not self.__is_exclusive() 788 assert self.__is_sharer() 789 790 return True 791 finally: 792 self.__lock.release()

793

794 - def release(self):

795 """Release a Shared Lock. 796 797 You must have acquired the lock, either in shared or in exclusive mode, 798 before calling this function. 799 800 """ 801 self.__lock.acquire() 802 try: 803 assert self.__is_exclusive() or self.__is_sharer(), \ 804 "Cannot release non-owned lock" 805 806 # Autodetect release type 807 if self.__is_exclusive(): 808 self.__exc = None 809 notify = True 810 else: 811 self.__shr.remove(threading.currentThread()) 812 notify = not self.__shr 813 814 # Notify topmost condition in queue if there are no owners left (for 815 # shared locks) 816 if notify: 817 self.__notify_topmost() 818 finally: 819 self.__lock.release()

820

821 - def __notify_topmost(self):

822 """Notifies topmost condition in queue of pending acquires. 823 824 """ 825 (priority, prioqueue) = self.__find_first_pending_queue() 826 if prioqueue: 827 cond = prioqueue[0] 828 cond.notifyAll() 829 if cond.shared: 830 # Prevent further shared acquires from sneaking in while waiters are 831 # notified 832 self.__pending_shared.pop(priority, None)

833

834 - def _notify_topmost(self):

835 """Exported version of L{__notify_topmost}. 836 837 """ 838 self.__lock.acquire() 839 try: 840 return self.__notify_topmost() 841 finally: 842 self.__lock.release()

843

844 - def delete(self, timeout=None, priority=None):

845 """Delete a Shared Lock. 846 847 This operation will declare the lock for removal. First the lock will be 848 acquired in exclusive mode if you don't already own it, then the lock 849 will be put in a state where any future and pending acquire() fail. 850 851 @type timeout: float 852 @param timeout: maximum waiting time before giving up 853 @type priority: integer 854 @param priority: Priority for acquiring lock 855 856 """ 857 if priority is None: 858 priority = _DEFAULT_PRIORITY 859 860 self.__lock.acquire() 861 try: 862 assert not self.__is_sharer(), "Cannot delete() a lock while sharing it" 863 864 self.__check_deleted() 865 866 # The caller is allowed to hold the lock exclusively already. 867 acquired = self.__is_exclusive() 868 869 if not acquired: 870 acquired = self.__acquire_unlocked(0, timeout, priority) 871 872 if acquired: 873 assert self.__is_exclusive() and not self.__is_sharer(), \ 874 "Lock wasn't acquired in exclusive mode" 875 876 self.__deleted = True 877 self.__exc = None 878 879 assert not (self.__exc or self.__shr), "Found owner during deletion" 880 881 # Notify all acquires. They'll throw an error. 882 for (_, prioqueue) in self.__pending: 883 for cond in prioqueue: 884 cond.notifyAll() 885 886 assert self.__deleted 887 888 return acquired 889 finally: 890 self.__lock.release()

891

892 - def _release_save(self):

893 shared = self.__is_sharer() 894 self.release() 895 return shared

896

897 - def _acquire_restore(self, shared):

898 self.acquire(shared=shared)

899 900 901 # Whenever we want to acquire a full LockSet we pass None as the value 902 # to acquire. Hide this behind this nicely named constant. 903 ALL_SET = None

904 905 906 -class _AcquireTimeout(Exception):

907 """Internal exception to abort an acquire on a timeout. 908 909 """

910

911 912 -class LockSet:

913 """Implements a set of locks. 914 915 This abstraction implements a set of shared locks for the same resource type, 916 distinguished by name. The user can lock a subset of the resources and the 917 LockSet will take care of acquiring the locks always in the same order, thus 918 preventing deadlock. 919 920 All the locks needed in the same set must be acquired together, though. 921 922 @type name: string 923 @ivar name: the name of the lockset 924 925 """

926 - def __init__(self, members, name, monitor=None):

927 """Constructs a new LockSet. 928 929 @type members: list of strings 930 @param members: initial members of the set 931 @type monitor: L{LockMonitor} 932 @param monitor: Lock monitor with which to register member locks 933 934 """ 935 assert members is not None, "members parameter is not a list" 936 self.name = name 937 938 # Lock monitor 939 self.__monitor = monitor 940 941 # Used internally to guarantee coherency 942 self.__lock = SharedLock(self._GetLockName("[lockset]"), monitor=monitor) 943 944 # The lockdict indexes the relationship name -> lock 945 # The order-of-locking is implied by the alphabetical order of names 946 self.__lockdict = {} 947 948 for mname in members: 949 self.__lockdict[mname] = SharedLock(self._GetLockName(mname), 950 monitor=monitor) 951 952 # The owner dict contains the set of locks each thread owns. For 953 # performance each thread can access its own key without a global lock on 954 # this structure. It is paramount though that *no* other type of access is 955 # done to this structure (eg. no looping over its keys). *_owner helper 956 # function are defined to guarantee access is correct, but in general never 957 # do anything different than __owners[threading.currentThread()], or there 958 # will be trouble. 959 self.__owners = {}

960

961 - def _GetLockName(self, mname):

962 """Returns the name for a member lock. 963 964 """ 965 return "%s/%s" % (self.name, mname)

966

967 - def _get_lock(self):

968 """Returns the lockset-internal lock. 969 970 """ 971 return self.__lock

972

973 - def _get_lockdict(self):

974 """Returns the lockset-internal lock dictionary. 975 976 Accessing this structure is only safe in single-thread usage or when the 977 lockset-internal lock is held. 978 979 """ 980 return self.__lockdict

981

982 - def is_owned(self):

983 """Is the current thread a current level owner? 984 985 @note: Use L{check_owned} to check if a specific lock is held 986 987 """ 988 return threading.currentThread() in self.__owners

989

990 - def check_owned(self, names, shared=-1):

991 """Check if locks are owned in a specific mode. 992 993 @type names: sequence or string 994 @param names: Lock names (or a single lock name) 995 @param shared: See L{SharedLock.is_owned} 996 @rtype: bool 997 @note: Use L{is_owned} to check if the current thread holds I{any} lock and 998 L{list_owned} to get the names of all owned locks 999 1000 """ 1001 if isinstance(names, basestring): 1002 names = [names] 1003 1004 # Avoid check if no locks are owned anyway 1005 if names and self.is_owned(): 1006 candidates = [] 1007 1008 # Gather references to all locks (in case they're deleted in the meantime) 1009 for lname in names: 1010 try: 1011 lock = self.__lockdict[lname] 1012 except KeyError: 1013 raise errors.LockError("Non-existing lock '%s' in set '%s' (it may" 1014 " have been removed)" % (lname, self.name)) 1015 else: 1016 candidates.append(lock) 1017 1018 return compat.all(lock.is_owned(shared=shared) for lock in candidates) 1019 else: 1020 return False

1021

1022 - def _add_owned(self, name=None):

1023 """Note the current thread owns the given lock""" 1024 if name is None: 1025 if not self.is_owned(): 1026 self.__owners[threading.currentThread()] = set() 1027 else: 1028 if self.is_owned(): 1029 self.__owners[threading.currentThread()].add(name) 1030 else: 1031 self.__owners[threading.currentThread()] = set([name])

1032

1033 - def _del_owned(self, name=None):

1034 """Note the current thread owns the given lock""" 1035 1036 assert not (name is None and self.__lock.is_owned()), \ 1037 "Cannot hold internal lock when deleting owner status" 1038 1039 if name is not None: 1040 self.__owners[threading.currentThread()].remove(name) 1041 1042 # Only remove the key if we don't hold the set-lock as well 1043 if (not self.__lock.is_owned() and 1044 not self.__owners[threading.currentThread()]): 1045 del self.__owners[threading.currentThread()]

1046

1047 - def list_owned(self):

1048 """Get the set of resource names owned by the current thread""" 1049 if self.is_owned(): 1050 return self.__owners[threading.currentThread()].copy() 1051 else: 1052 return set()

1053

1054 - def _release_and_delete_owned(self):

1055 """Release and delete all resources owned by the current thread""" 1056 for lname in self.list_owned(): 1057 lock = self.__lockdict[lname] 1058 if lock.is_owned(): 1059 lock.release() 1060 self._del_owned(name=lname)

1061

1062 - def __names(self):

1063 """Return the current set of names. 1064 1065 Only call this function while holding __lock and don't iterate on the 1066 result after releasing the lock. 1067 1068 """ 1069 return self.__lockdict.keys()

1070

1071 - def _names(self):

1072 """Return a copy of the current set of elements. 1073 1074 Used only for debugging purposes. 1075 1076 """ 1077 # If we don't already own the set-level lock acquired 1078 # we'll get it and note we need to release it later. 1079 release_lock = False 1080 if not self.__lock.is_owned(): 1081 release_lock = True 1082 self.__lock.acquire(shared=1) 1083 try: 1084 result = self.__names() 1085 finally: 1086 if release_lock: 1087 self.__lock.release() 1088 return set(result)

1089

1090 - def acquire(self, names, timeout=None, shared=0, priority=None, 1091 test_notify=None):

1092 """Acquire a set of resource locks. 1093 1094 @type names: list of strings (or string) 1095 @param names: the names of the locks which shall be acquired 1096 (special lock names, or instance/node names) 1097 @type shared: integer (0/1) used as a boolean 1098 @param shared: whether to acquire in shared mode; by default an 1099 exclusive lock will be acquired 1100 @type timeout: float or None 1101 @param timeout: Maximum time to acquire all locks 1102 @type priority: integer 1103 @param priority: Priority for acquiring locks 1104 @type test_notify: callable or None 1105 @param test_notify: Special callback function for unittesting 1106 1107 @return: Set of all locks successfully acquired or None in case of timeout 1108 1109 @raise errors.LockError: when any lock we try to acquire has 1110 been deleted before we succeed. In this case none of the 1111 locks requested will be acquired. 1112 1113 """ 1114 assert timeout is None or timeout >= 0.0 1115 1116 # Check we don't already own locks at this level 1117 assert not self.is_owned(), ("Cannot acquire locks in the same set twice" 1118 " (lockset %s)" % self.name) 1119 1120 if priority is None: 1121 priority = _DEFAULT_PRIORITY 1122 1123 # We need to keep track of how long we spent waiting for a lock. The 1124 # timeout passed to this function is over all lock acquires. 1125 running_timeout = utils.RunningTimeout(timeout, False) 1126 1127 try: 1128 if names is not None: 1129 # Support passing in a single resource to acquire rather than many 1130 if isinstance(names, basestring): 1131 names = [names] 1132 1133 return self.__acquire_inner(names, False, shared, priority, 1134 running_timeout.Remaining, test_notify) 1135 1136 else: 1137 # If no names are given acquire the whole set by not letting new names 1138 # being added before we release, and getting the current list of names. 1139 # Some of them may then be deleted later, but we'll cope with this. 1140 # 1141 # We'd like to acquire this lock in a shared way, as it's nice if 1142 # everybody else can use the instances at the same time. If we are 1143 # acquiring them exclusively though they won't be able to do this 1144 # anyway, though, so we'll get the list lock exclusively as well in 1145 # order to be able to do add() on the set while owning it. 1146 if not self.__lock.acquire(shared=shared, priority=priority, 1147 timeout=running_timeout.Remaining()): 1148 raise _AcquireTimeout() 1149 try: 1150 # note we own the set-lock 1151 self._add_owned() 1152 1153 return self.__acquire_inner(self.__names(), True, shared, priority, 1154 running_timeout.Remaining, test_notify) 1155 except: 1156 # We shouldn't have problems adding the lock to the owners list, but 1157 # if we did we'll try to release this lock and re-raise exception. 1158 # Of course something is going to be really wrong, after this. 1159 self.__lock.release() 1160 self._del_owned() 1161 raise 1162 1163 except _AcquireTimeout: 1164 return None

1165

1166 - def __acquire_inner(self, names, want_all, shared, priority, 1167 timeout_fn, test_notify):

1168 """Inner logic for acquiring a number of locks. 1169 1170 @param names: Names of the locks to be acquired 1171 @param want_all: Whether all locks in the set should be acquired 1172 @param shared: Whether to acquire in shared mode 1173 @param timeout_fn: Function returning remaining timeout 1174 @param priority: Priority for acquiring locks 1175 @param test_notify: Special callback function for unittesting 1176 1177 """ 1178 acquire_list = [] 1179 1180 # First we look the locks up on __lockdict. We have no way of being sure 1181 # they will still be there after, but this makes it a lot faster should 1182 # just one of them be the already wrong. Using a sorted sequence to prevent 1183 # deadlocks. 1184 for lname in sorted(utils.UniqueSequence(names)): 1185 try: 1186 lock = self.__lockdict[lname] # raises KeyError if lock is not there 1187 except KeyError: 1188 if want_all: 1189 # We are acquiring all the set, it doesn't matter if this particular 1190 # element is not there anymore. 1191 continue 1192 1193 raise errors.LockError("Non-existing lock %s in set %s (it may have" 1194 " been removed)" % (lname, self.name)) 1195 1196 acquire_list.append((lname, lock)) 1197 1198 # This will hold the locknames we effectively acquired. 1199 acquired = set() 1200 1201 try: 1202 # Now acquire_list contains a sorted list of resources and locks we 1203 # want. In order to get them we loop on this (private) list and 1204 # acquire() them. We gave no real guarantee they will still exist till 1205 # this is done but .acquire() itself is safe and will alert us if the 1206 # lock gets deleted. 1207 for (lname, lock) in acquire_list: 1208 if __debug__ and callable(test_notify): 1209 test_notify_fn = lambda: test_notify(lname) 1210 else: 1211 test_notify_fn = None 1212 1213 timeout = timeout_fn() 1214 1215 try: 1216 # raises LockError if the lock was deleted 1217 acq_success = lock.acquire(shared=shared, timeout=timeout, 1218 priority=priority, 1219 test_notify=test_notify_fn) 1220 except errors.LockError: 1221 if want_all: 1222 # We are acquiring all the set, it doesn't matter if this 1223 # particular element is not there anymore. 1224 continue 1225 1226 raise errors.LockError("Non-existing lock %s in set %s (it may" 1227 " have been removed)" % (lname, self.name)) 1228 1229 if not acq_success: 1230 # Couldn't get lock or timeout occurred 1231 if timeout is None: 1232 # This shouldn't happen as SharedLock.acquire(timeout=None) is 1233 # blocking. 1234 raise errors.LockError("Failed to get lock %s (set %s)" % 1235 (lname, self.name)) 1236 1237 raise _AcquireTimeout() 1238 1239 try: 1240 # now the lock cannot be deleted, we have it! 1241 self._add_owned(name=lname) 1242 acquired.add(lname) 1243 1244 except: 1245 # We shouldn't have problems adding the lock to the owners list, but 1246 # if we did we'll try to release this lock and re-raise exception. 1247 # Of course something is going to be really wrong after this. 1248 if lock.is_owned(): 1249 lock.release() 1250 raise 1251 1252 except: 1253 # Release all owned locks 1254 self._release_and_delete_owned() 1255 raise 1256 1257 return acquired

1258

1259 - def downgrade(self, names=None):

1260 """Downgrade a set of resource locks from exclusive to shared mode. 1261 1262 The locks must have been acquired in exclusive mode. 1263 1264 """ 1265 assert self.is_owned(), ("downgrade on lockset %s while not owning any" 1266 " lock" % self.name) 1267 1268 # Support passing in a single resource to downgrade rather than many 1269 if isinstance(names, basestring): 1270 names = [names] 1271 1272 owned = self.list_owned() 1273 1274 if names is None: 1275 names = owned 1276 else: 1277 names = set(names) 1278 assert owned.issuperset(names), \ 1279 ("downgrade() on unheld resources %s (set %s)" % 1280 (names.difference(owned), self.name)) 1281 1282 for lockname in names: 1283 self.__lockdict[lockname].downgrade() 1284 1285 # Do we own the lockset in exclusive mode? 1286 if self.__lock.is_owned(shared=0): 1287 # Have all locks been downgraded? 1288 if not compat.any(lock.is_owned(shared=0) 1289 for lock in self.__lockdict.values()): 1290 self.__lock.downgrade() 1291 assert self.__lock.is_owned(shared=1) 1292 1293 return True

1294

1295 - def release(self, names=None):

1296 """Release a set of resource locks, at the same level. 1297 1298 You must have acquired the locks, either in shared or in exclusive mode, 1299 before releasing them. 1300 1301 @type names: list of strings, or None 1302 @param names: the names of the locks which shall be released 1303 (defaults to all the locks acquired at that level). 1304 1305 """ 1306 assert self.is_owned(), ("release() on lock set %s while not owner" % 1307 self.name) 1308 1309 # Support passing in a single resource to release rather than many 1310 if isinstance(names, basestring): 1311 names = [names] 1312 1313 if names is None: 1314 names = self.list_owned() 1315 else: 1316 names = set(names) 1317 assert self.list_owned().issuperset(names), ( 1318 "release() on unheld resources %s (set %s)" % 1319 (names.difference(self.list_owned()), self.name)) 1320 1321 # First of all let's release the "all elements" lock, if set. 1322 # After this 'add' can work again 1323 if self.__lock.is_owned(): 1324 self.__lock.release() 1325 self._del_owned() 1326 1327 for lockname in names: 1328 # If we are sure the lock doesn't leave __lockdict without being 1329 # exclusively held we can do this... 1330 self.__lockdict[lockname].release() 1331 self._del_owned(name=lockname)

1332

1333 - def add(self, names, acquired=0, shared=0):

1334 """Add a new set of elements to the set 1335 1336 @type names: list of strings 1337 @param names: names of the new elements to add 1338 @type acquired: integer (0/1) used as a boolean 1339 @param acquired: pre-acquire the new resource? 1340 @type shared: integer (0/1) used as a boolean 1341 @param shared: is the pre-acquisition shared? 1342 1343 """ 1344 # Check we don't already own locks at this level 1345 assert not self.is_owned() or self.__lock.is_owned(shared=0), \ 1346 ("Cannot add locks if the set %s is only partially owned, or shared" % 1347 self.name) 1348 1349 # Support passing in a single resource to add rather than many 1350 if isinstance(names, basestring): 1351 names = [names] 1352 1353 # If we don't already own the set-level lock acquired in an exclusive way 1354 # we'll get it and note we need to release it later. 1355 release_lock = False 1356 if not self.__lock.is_owned(): 1357 release_lock = True 1358 self.__lock.acquire() 1359 1360 try: 1361 invalid_names = set(self.__names()).intersection(names) 1362 if invalid_names: 1363 # This must be an explicit raise, not an assert, because assert is 1364 # turned off when using optimization, and this can happen because of 1365 # concurrency even if the user doesn't want it. 1366 raise errors.LockError("duplicate add(%s) on lockset %s" % 1367 (invalid_names, self.name)) 1368 1369 for lockname in names: 1370 lock = SharedLock(self._GetLockName(lockname), monitor=self.__monitor) 1371 1372 if acquired: 1373 # No need for priority or timeout here as this lock has just been 1374 # created 1375 lock.acquire(shared=shared) 1376 # now the lock cannot be deleted, we have it! 1377 try: 1378 self._add_owned(name=lockname) 1379 except: 1380 # We shouldn't have problems adding the lock to the owners list, 1381 # but if we did we'll try to release this lock and re-raise 1382 # exception. Of course something is going to be really wrong, 1383 # after this. On the other hand the lock hasn't been added to the 1384 # __lockdict yet so no other threads should be pending on it. This 1385 # release is just a safety measure. 1386 lock.release() 1387 raise 1388 1389 self.__lockdict[lockname] = lock 1390 1391 finally: 1392 # Only release __lock if we were not holding it previously. 1393 if release_lock: 1394 self.__lock.release() 1395 1396 return True

1397

1398 - def remove(self, names):

1399 """Remove elements from the lock set. 1400 1401 You can either not hold anything in the lockset or already hold a superset 1402 of the elements you want to delete, exclusively. 1403 1404 @type names: list of strings 1405 @param names: names of the resource to remove. 1406 1407 @return: a list of locks which we removed; the list is always 1408 equal to the names list if we were holding all the locks 1409 exclusively 1410 1411 """ 1412 # Support passing in a single resource to remove rather than many 1413 if isinstance(names, basestring): 1414 names = [names] 1415 1416 # If we own any subset of this lock it must be a superset of what we want 1417 # to delete. The ownership must also be exclusive, but that will be checked 1418 # by the lock itself. 1419 assert not self.is_owned() or self.list_owned().issuperset(names), ( 1420 "remove() on acquired lockset %s while not owning all elements" % 1421 self.name) 1422 1423 removed = [] 1424 1425 for lname in names: 1426 # Calling delete() acquires the lock exclusively if we don't already own 1427 # it, and causes all pending and subsequent lock acquires to fail. It's 1428 # fine to call it out of order because delete() also implies release(), 1429 # and the assertion above guarantees that if we either already hold 1430 # everything we want to delete, or we hold none. 1431 try: 1432 self.__lockdict[lname].delete() 1433 removed.append(lname) 1434 except (KeyError, errors.LockError): 1435 # This cannot happen if we were already holding it, verify: 1436 assert not self.is_owned(), ("remove failed while holding lockset %s" % 1437 self.name) 1438 else: 1439 # If no LockError was raised we are the ones who deleted the lock. 1440 # This means we can safely remove it from lockdict, as any further or 1441 # pending delete() or acquire() will fail (and nobody can have the lock 1442 # since before our call to delete()). 1443 # 1444 # This is done in an else clause because if the exception was thrown 1445 # it's the job of the one who actually deleted it. 1446 del self.__lockdict[lname] 1447 # And let's remove it from our private list if we owned it. 1448 if self.is_owned(): 1449 self._del_owned(name=lname) 1450 1451 return removed

1452 1453 1454 # Locking levels, must be acquired in increasing order. 1455 # Current rules are: 1456 # - at level LEVEL_CLUSTER resides the Big Ganeti Lock (BGL) which must be 1457 # acquired before performing any operation, either in shared or in exclusive 1458 # mode. acquiring the BGL in exclusive mode is discouraged and should be 1459 # avoided. 1460 # - at levels LEVEL_NODE and LEVEL_INSTANCE reside node and instance locks. 1461 # If you need more than one node, or more than one instance, acquire them at 1462 # the same time. 1463 LEVEL_CLUSTER = 0 1464 LEVEL_INSTANCE = 1 1465 LEVEL_NODEGROUP = 2 1466 LEVEL_NODE = 3 1467 LEVEL_NODE_RES = 4 1468 1469 LEVELS = [ 1470 LEVEL_CLUSTER, 1471 LEVEL_INSTANCE, 1472 LEVEL_NODEGROUP, 1473 LEVEL_NODE, 1474 LEVEL_NODE_RES, 1475 ] 1476 1477 # Lock levels which are modifiable 1478 LEVELS_MOD = frozenset([ 1479 LEVEL_NODE_RES, 1480 LEVEL_NODE, 1481 LEVEL_NODEGROUP, 1482 LEVEL_INSTANCE, 1483 ]) 1484 1485 #: Lock level names (make sure to use singular form) 1486 LEVEL_NAMES = { 1487 LEVEL_CLUSTER: "cluster", 1488 LEVEL_INSTANCE: "instance", 1489 LEVEL_NODEGROUP: "nodegroup", 1490 LEVEL_NODE: "node", 1491 LEVEL_NODE_RES: "node-res", 1492 } 1493 1494 # Constant for the big ganeti lock 1495 BGL = "BGL"

1496 1497 1498 -class GanetiLockManager:

1499 """The Ganeti Locking Library 1500 1501 The purpose of this small library is to manage locking for ganeti clusters 1502 in a central place, while at the same time doing dynamic checks against 1503 possible deadlocks. It will also make it easier to transition to a different 1504 lock type should we migrate away from python threads. 1505 1506 """ 1507 _instance = None 1508

1509 - def __init__(self, nodes, nodegroups, instances):

1510 """Constructs a new GanetiLockManager object. 1511 1512 There should be only a GanetiLockManager object at any time, so this 1513 function raises an error if this is not the case. 1514 1515 @param nodes: list of node names 1516 @param nodegroups: list of nodegroup uuids 1517 @param instances: list of instance names 1518 1519 """ 1520 assert self.__class__._instance is None, \ 1521 "double GanetiLockManager instance" 1522 1523 self.__class__._instance = self 1524 1525 self._monitor = LockMonitor() 1526 1527 # The keyring contains all the locks, at their level and in the correct 1528 # locking order. 1529 self.__keyring = { 1530 LEVEL_CLUSTER: LockSet([BGL], "cluster", monitor=self._monitor), 1531 LEVEL_NODE: LockSet(nodes, "node", monitor=self._monitor), 1532 LEVEL_NODE_RES: LockSet(nodes, "node-res", monitor=self._monitor), 1533 LEVEL_NODEGROUP: LockSet(nodegroups, "nodegroup", monitor=self._monitor), 1534 LEVEL_INSTANCE: LockSet(instances, "instance", 1535 monitor=self._monitor), 1536 } 1537 1538 assert compat.all(ls.name == LEVEL_NAMES[level] 1539 for (level, ls) in self.__keyring.items())

1540

1541 - def AddToLockMonitor(self, provider):

1542 """Registers a new lock with the monitor. 1543 1544 See L{LockMonitor.RegisterLock}. 1545 1546 """ 1547 return self._monitor.RegisterLock(provider)

1548

1549 - def QueryLocks(self, fields):

1550 """Queries information from all locks. 1551 1552 See L{LockMonitor.QueryLocks}. 1553 1554 """ 1555 return self._monitor.QueryLocks(fields)

1556

1557 - def _names(self, level):

1558 """List the lock names at the given level. 1559 1560 This can be used for debugging/testing purposes. 1561 1562 @param level: the level whose list of locks to get 1563 1564 """ 1565 assert level in LEVELS, "Invalid locking level %s" % level 1566 return self.__keyring[level]._names()

1567

1568 - def is_owned(self, level):

1569 """Check whether we are owning locks at the given level 1570 1571 """ 1572 return self.__keyring[level].is_owned()

1573

1574 - def list_owned(self, level):

1575 """Get the set of owned locks at the given level 1576 1577 """ 1578 return self.__keyring[level].list_owned()

1579

1580 - def check_owned(self, level, names, shared=-1):

1581 """Check if locks at a certain level are owned in a specific mode. 1582 1583 @see: L{LockSet.check_owned} 1584 1585 """ 1586 return self.__keyring[level].check_owned(names, shared=shared)

1587

1588 - def _upper_owned(self, level):

1589 """Check that we don't own any lock at a level greater than the given one. 1590 1591 """ 1592 # This way of checking only works if LEVELS[i] = i, which we check for in 1593 # the test cases. 1594 return compat.any((self.is_owned(l) for l in LEVELS[level + 1:]))

1595

1596 - def _BGL_owned(self): # pylint: disable=C0103

1597 """Check if the current thread owns the BGL. 1598 1599 Both an exclusive or a shared acquisition work. 1600 1601 """ 1602 return BGL in self.__keyring[LEVEL_CLUSTER].list_owned()

1603 1604 @staticmethod

1605 - def _contains_BGL(level, names): # pylint: disable=C0103

1606 """Check if the level contains the BGL. 1607 1608 Check if acting on the given level and set of names will change 1609 the status of the Big Ganeti Lock. 1610 1611 """ 1612 return level == LEVEL_CLUSTER and (names is None or BGL in names) 1613

1614 - def acquire(self, level, names, timeout=None, shared=0, priority=None):

1615 """Acquire a set of resource locks, at the same level. 1616 1617 @type level: member of locking.LEVELS 1618 @param level: the level at which the locks shall be acquired 1619 @type names: list of strings (or string) 1620 @param names: the names of the locks which shall be acquired 1621 (special lock names, or instance/node names) 1622 @type shared: integer (0/1) used as a boolean 1623 @param shared: whether to acquire in shared mode; by default 1624 an exclusive lock will be acquired 1625 @type timeout: float 1626 @param timeout: Maximum time to acquire all locks 1627 @type priority: integer 1628 @param priority: Priority for acquiring lock 1629 1630 """ 1631 assert level in LEVELS, "Invalid locking level %s" % level 1632 1633 # Check that we are either acquiring the Big Ganeti Lock or we already own 1634 # it. Some "legacy" opcodes need to be sure they are run non-concurrently 1635 # so even if we've migrated we need to at least share the BGL to be 1636 # compatible with them. Of course if we own the BGL exclusively there's no 1637 # point in acquiring any other lock, unless perhaps we are half way through 1638 # the migration of the current opcode. 1639 assert (self._contains_BGL(level, names) or self._BGL_owned()), ( 1640 "You must own the Big Ganeti Lock before acquiring any other") 1641 1642 # Check we don't own locks at the same or upper levels. 1643 assert not self._upper_owned(level), ("Cannot acquire locks at a level" 1644 " while owning some at a greater one") 1645 1646 # Acquire the locks in the set. 1647 return self.__keyring[level].acquire(names, shared=shared, timeout=timeout, 1648 priority=priority)

1649

1650 - def downgrade(self, level, names=None):

1651 """Downgrade a set of resource locks from exclusive to shared mode. 1652 1653 You must have acquired the locks in exclusive mode. 1654 1655 @type level: member of locking.LEVELS 1656 @param level: the level at which the locks shall be downgraded 1657 @type names: list of strings, or None 1658 @param names: the names of the locks which shall be downgraded 1659 (defaults to all the locks acquired at the level) 1660 1661 """ 1662 assert level in LEVELS, "Invalid locking level %s" % level 1663 1664 return self.__keyring[level].downgrade(names=names)

1665

1666 - def release(self, level, names=None):

1667 """Release a set of resource locks, at the same level. 1668 1669 You must have acquired the locks, either in shared or in exclusive 1670 mode, before releasing them. 1671 1672 @type level: member of locking.LEVELS 1673 @param level: the level at which the locks shall be released 1674 @type names: list of strings, or None 1675 @param names: the names of the locks which shall be released 1676 (defaults to all the locks acquired at that level) 1677 1678 """ 1679 assert level in LEVELS, "Invalid locking level %s" % level 1680 assert (not self._contains_BGL(level, names) or 1681 not self._upper_owned(LEVEL_CLUSTER)), ( 1682 "Cannot release the Big Ganeti Lock while holding something" 1683 " at upper levels (%r)" % 1684 (utils.CommaJoin(["%s=%r" % (LEVEL_NAMES[i], self.list_owned(i)) 1685 for i in self.__keyring.keys()]), )) 1686 1687 # Release will complain if we don't own the locks already 1688 return self.__keyring[level].release(names)

1689

1690 - def add(self, level, names, acquired=0, shared=0):

1691 """Add locks at the specified level. 1692 1693 @type level: member of locking.LEVELS_MOD 1694 @param level: the level at which the locks shall be added 1695 @type names: list of strings 1696 @param names: names of the locks to acquire 1697 @type acquired: integer (0/1) used as a boolean 1698 @param acquired: whether to acquire the newly added locks 1699 @type shared: integer (0/1) used as a boolean 1700 @param shared: whether the acquisition will be shared 1701 1702 """ 1703 assert level in LEVELS_MOD, "Invalid or immutable level %s" % level 1704 assert self._BGL_owned(), ("You must own the BGL before performing other" 1705 " operations") 1706 assert not self._upper_owned(level), ("Cannot add locks at a level" 1707 " while owning some at a greater one") 1708 return self.__keyring[level].add(names, acquired=acquired, shared=shared)

1709

1710 - def remove(self, level, names):

1711 """Remove locks from the specified level. 1712 1713 You must either already own the locks you are trying to remove 1714 exclusively or not own any lock at an upper level. 1715 1716 @type level: member of locking.LEVELS_MOD 1717 @param level: the level at which the locks shall be removed 1718 @type names: list of strings 1719 @param names: the names of the locks which shall be removed 1720 (special lock names, or instance/node names) 1721 1722 """ 1723 assert level in LEVELS_MOD, "Invalid or immutable level %s" % level 1724 assert self._BGL_owned(), ("You must own the BGL before performing other" 1725 " operations") 1726 # Check we either own the level or don't own anything from here 1727 # up. LockSet.remove() will check the case in which we don't own 1728 # all the needed resources, or we have a shared ownership. 1729 assert self.is_owned(level) or not self._upper_owned(level), ( 1730 "Cannot remove locks at a level while not owning it or" 1731 " owning some at a greater one") 1732 return self.__keyring[level].remove(names)

1733

1734 1735 -def _MonitorSortKey((item, idx, num)):

1736 """Sorting key function. 1737 1738 Sort by name, registration order and then order of information. This provides 1739 a stable sort order over different providers, even if they return the same 1740 name. 1741 1742 """ 1743 (name, _, _, _) = item 1744 1745 return (utils.NiceSortKey(name), num, idx)

1746

1747 1748 -class LockMonitor(object):

1749 _LOCK_ATTR = "_lock" 1750

1751 - def __init__(self):

1752 """Initializes this class. 1753 1754 """ 1755 self._lock = SharedLock("LockMonitor") 1756 1757 # Counter for stable sorting 1758 self._counter = itertools.count(0) 1759 1760 # Tracked locks. Weak references are used to avoid issues with circular 1761 # references and deletion. 1762 self._locks = weakref.WeakKeyDictionary()

1763 1764 @ssynchronized(_LOCK_ATTR)

1765 - def RegisterLock(self, provider):

1766 """Registers a new lock. 1767 1768 @param provider: Object with a callable method named C{GetLockInfo}, taking 1769 a single C{set} containing the requested information items 1770 @note: It would be nicer to only receive the function generating the 1771 requested information but, as it turns out, weak references to bound 1772 methods (e.g. C{self.GetLockInfo}) are tricky; there are several 1773 workarounds, but none of the ones I found works properly in combination 1774 with a standard C{WeakKeyDictionary} 1775 1776 """ 1777 assert provider not in self._locks, "Duplicate registration" 1778 1779 # There used to be a check for duplicate names here. As it turned out, when 1780 # a lock is re-created with the same name in a very short timeframe, the 1781 # previous instance might not yet be removed from the weakref dictionary. 1782 # By keeping track of the order of incoming registrations, a stable sort 1783 # ordering can still be guaranteed. 1784 1785 self._locks[provider] = self._counter.next()

1786

1787 - def _GetLockInfo(self, requested):

1788 """Get information from all locks. 1789 1790 """ 1791 # Must hold lock while getting consistent list of tracked items 1792 self._lock.acquire(shared=1) 1793 try: 1794 items = self._locks.items() 1795 finally: 1796 self._lock.release() 1797 1798 return [(info, idx, num) 1799 for (provider, num) in items 1800 for (idx, info) in enumerate(provider.GetLockInfo(requested))]

1801

1802 - def _Query(self, fields):

1803 """Queries information from all locks. 1804 1805 @type fields: list of strings 1806 @param fields: List of fields to return 1807 1808 """ 1809 qobj = query.Query(query.LOCK_FIELDS, fields) 1810 1811 # Get all data with internal lock held and then sort by name and incoming 1812 # order 1813 lockinfo = sorted(self._GetLockInfo(qobj.RequestedData()), 1814 key=_MonitorSortKey) 1815 1816 # Extract lock information and build query data 1817 return (qobj, query.LockQueryData(map(compat.fst, lockinfo)))

1818

1819 - def QueryLocks(self, fields):

1820 """Queries information from all locks. 1821 1822 @type fields: list of strings 1823 @param fields: List of fields to return 1824 1825 """ 1826 (qobj, ctx) = self._Query(fields) 1827 1828 # Prepare query response 1829 return query.GetQueryResponse(qobj, ctx)

1830

Source Code for Module ganeti.locking