root / lib / locking.py @ ba174485
History | View | Annotate | Download (61.1 kB)
1 |
#
|
---|---|
2 |
#
|
3 |
|
4 |
# Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 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 |
#: Minimum timeout required to consider scheduling a pending acquisition
|
51 |
#: (seconds)
|
52 |
_LOCK_ACQUIRE_MIN_TIMEOUT = (1.0 / 1000) |
53 |
|
54 |
# Internal lock acquisition modes for L{LockSet}
|
55 |
(_LS_ACQUIRE_EXACT, |
56 |
_LS_ACQUIRE_ALL, |
57 |
_LS_ACQUIRE_OPPORTUNISTIC) = range(1, 4) |
58 |
|
59 |
_LS_ACQUIRE_MODES = compat.UniqueFrozenset([ |
60 |
_LS_ACQUIRE_EXACT, |
61 |
_LS_ACQUIRE_ALL, |
62 |
_LS_ACQUIRE_OPPORTUNISTIC, |
63 |
]) |
64 |
|
65 |
|
66 |
def ssynchronized(mylock, shared=0): |
67 |
"""Shared Synchronization decorator.
|
68 |
|
69 |
Calls the function holding the given lock, either in exclusive or shared
|
70 |
mode. It requires the passed lock to be a SharedLock (or support its
|
71 |
semantics).
|
72 |
|
73 |
@type mylock: lockable object or string
|
74 |
@param mylock: lock to acquire or class member name of the lock to acquire
|
75 |
|
76 |
"""
|
77 |
def wrap(fn): |
78 |
def sync_function(*args, **kwargs): |
79 |
if isinstance(mylock, basestring): |
80 |
assert args, "cannot ssynchronize on non-class method: self not found" |
81 |
# args[0] is "self"
|
82 |
lock = getattr(args[0], mylock) |
83 |
else:
|
84 |
lock = mylock |
85 |
lock.acquire(shared=shared) |
86 |
try:
|
87 |
return fn(*args, **kwargs)
|
88 |
finally:
|
89 |
lock.release() |
90 |
return sync_function
|
91 |
return wrap
|
92 |
|
93 |
|
94 |
class _SingleNotifyPipeConditionWaiter(object): |
95 |
"""Helper class for SingleNotifyPipeCondition
|
96 |
|
97 |
"""
|
98 |
__slots__ = [ |
99 |
"_fd",
|
100 |
"_poller",
|
101 |
] |
102 |
|
103 |
def __init__(self, poller, fd): |
104 |
"""Constructor for _SingleNotifyPipeConditionWaiter
|
105 |
|
106 |
@type poller: select.poll
|
107 |
@param poller: Poller object
|
108 |
@type fd: int
|
109 |
@param fd: File descriptor to wait for
|
110 |
|
111 |
"""
|
112 |
object.__init__(self) |
113 |
self._poller = poller
|
114 |
self._fd = fd
|
115 |
|
116 |
def __call__(self, timeout): |
117 |
"""Wait for something to happen on the pipe.
|
118 |
|
119 |
@type timeout: float or None
|
120 |
@param timeout: Timeout for waiting (can be None)
|
121 |
|
122 |
"""
|
123 |
running_timeout = utils.RunningTimeout(timeout, True)
|
124 |
|
125 |
while True: |
126 |
remaining_time = running_timeout.Remaining() |
127 |
|
128 |
if remaining_time is not None: |
129 |
if remaining_time < 0.0: |
130 |
break
|
131 |
|
132 |
# Our calculation uses seconds, poll() wants milliseconds
|
133 |
remaining_time *= 1000
|
134 |
|
135 |
try:
|
136 |
result = self._poller.poll(remaining_time)
|
137 |
except EnvironmentError, err: |
138 |
if err.errno != errno.EINTR:
|
139 |
raise
|
140 |
result = None
|
141 |
|
142 |
# Check whether we were notified
|
143 |
if result and result[0][0] == self._fd: |
144 |
break
|
145 |
|
146 |
|
147 |
class _BaseCondition(object): |
148 |
"""Base class containing common code for conditions.
|
149 |
|
150 |
Some of this code is taken from python's threading module.
|
151 |
|
152 |
"""
|
153 |
__slots__ = [ |
154 |
"_lock",
|
155 |
"acquire",
|
156 |
"release",
|
157 |
"_is_owned",
|
158 |
"_acquire_restore",
|
159 |
"_release_save",
|
160 |
] |
161 |
|
162 |
def __init__(self, lock): |
163 |
"""Constructor for _BaseCondition.
|
164 |
|
165 |
@type lock: threading.Lock
|
166 |
@param lock: condition base lock
|
167 |
|
168 |
"""
|
169 |
object.__init__(self) |
170 |
|
171 |
try:
|
172 |
self._release_save = lock._release_save
|
173 |
except AttributeError: |
174 |
self._release_save = self._base_release_save |
175 |
try:
|
176 |
self._acquire_restore = lock._acquire_restore
|
177 |
except AttributeError: |
178 |
self._acquire_restore = self._base_acquire_restore |
179 |
try:
|
180 |
self._is_owned = lock.is_owned
|
181 |
except AttributeError: |
182 |
self._is_owned = self._base_is_owned |
183 |
|
184 |
self._lock = lock
|
185 |
|
186 |
# Export the lock's acquire() and release() methods
|
187 |
self.acquire = lock.acquire
|
188 |
self.release = lock.release
|
189 |
|
190 |
def _base_is_owned(self): |
191 |
"""Check whether lock is owned by current thread.
|
192 |
|
193 |
"""
|
194 |
if self._lock.acquire(0): |
195 |
self._lock.release()
|
196 |
return False |
197 |
return True |
198 |
|
199 |
def _base_release_save(self): |
200 |
self._lock.release()
|
201 |
|
202 |
def _base_acquire_restore(self, _): |
203 |
self._lock.acquire()
|
204 |
|
205 |
def _check_owned(self): |
206 |
"""Raise an exception if the current thread doesn't own the lock.
|
207 |
|
208 |
"""
|
209 |
if not self._is_owned(): |
210 |
raise RuntimeError("cannot work with un-aquired lock") |
211 |
|
212 |
|
213 |
class SingleNotifyPipeCondition(_BaseCondition): |
214 |
"""Condition which can only be notified once.
|
215 |
|
216 |
This condition class uses pipes and poll, internally, to be able to wait for
|
217 |
notification with a timeout, without resorting to polling. It is almost
|
218 |
compatible with Python's threading.Condition, with the following differences:
|
219 |
- notifyAll can only be called once, and no wait can happen after that
|
220 |
- notify is not supported, only notifyAll
|
221 |
|
222 |
"""
|
223 |
|
224 |
__slots__ = [ |
225 |
"_poller",
|
226 |
"_read_fd",
|
227 |
"_write_fd",
|
228 |
"_nwaiters",
|
229 |
"_notified",
|
230 |
] |
231 |
|
232 |
_waiter_class = _SingleNotifyPipeConditionWaiter |
233 |
|
234 |
def __init__(self, lock): |
235 |
"""Constructor for SingleNotifyPipeCondition
|
236 |
|
237 |
"""
|
238 |
_BaseCondition.__init__(self, lock)
|
239 |
self._nwaiters = 0 |
240 |
self._notified = False |
241 |
self._read_fd = None |
242 |
self._write_fd = None |
243 |
self._poller = None |
244 |
|
245 |
def _check_unnotified(self): |
246 |
"""Throws an exception if already notified.
|
247 |
|
248 |
"""
|
249 |
if self._notified: |
250 |
raise RuntimeError("cannot use already notified condition") |
251 |
|
252 |
def _Cleanup(self): |
253 |
"""Cleanup open file descriptors, if any.
|
254 |
|
255 |
"""
|
256 |
if self._read_fd is not None: |
257 |
os.close(self._read_fd)
|
258 |
self._read_fd = None |
259 |
|
260 |
if self._write_fd is not None: |
261 |
os.close(self._write_fd)
|
262 |
self._write_fd = None |
263 |
self._poller = None |
264 |
|
265 |
def wait(self, timeout): |
266 |
"""Wait for a notification.
|
267 |
|
268 |
@type timeout: float or None
|
269 |
@param timeout: Waiting timeout (can be None)
|
270 |
|
271 |
"""
|
272 |
self._check_owned()
|
273 |
self._check_unnotified()
|
274 |
|
275 |
self._nwaiters += 1 |
276 |
try:
|
277 |
if self._poller is None: |
278 |
(self._read_fd, self._write_fd) = os.pipe() |
279 |
self._poller = select.poll()
|
280 |
self._poller.register(self._read_fd, select.POLLHUP) |
281 |
|
282 |
wait_fn = self._waiter_class(self._poller, self._read_fd) |
283 |
state = self._release_save()
|
284 |
try:
|
285 |
# Wait for notification
|
286 |
wait_fn(timeout) |
287 |
finally:
|
288 |
# Re-acquire lock
|
289 |
self._acquire_restore(state)
|
290 |
finally:
|
291 |
self._nwaiters -= 1 |
292 |
if self._nwaiters == 0: |
293 |
self._Cleanup()
|
294 |
|
295 |
def notifyAll(self): # pylint: disable=C0103 |
296 |
"""Close the writing side of the pipe to notify all waiters.
|
297 |
|
298 |
"""
|
299 |
self._check_owned()
|
300 |
self._check_unnotified()
|
301 |
self._notified = True |
302 |
if self._write_fd is not None: |
303 |
os.close(self._write_fd)
|
304 |
self._write_fd = None |
305 |
|
306 |
|
307 |
class PipeCondition(_BaseCondition): |
308 |
"""Group-only non-polling condition with counters.
|
309 |
|
310 |
This condition class uses pipes and poll, internally, to be able to wait for
|
311 |
notification with a timeout, without resorting to polling. It is almost
|
312 |
compatible with Python's threading.Condition, but only supports notifyAll and
|
313 |
non-recursive locks. As an additional features it's able to report whether
|
314 |
there are any waiting threads.
|
315 |
|
316 |
"""
|
317 |
__slots__ = [ |
318 |
"_waiters",
|
319 |
"_single_condition",
|
320 |
] |
321 |
|
322 |
_single_condition_class = SingleNotifyPipeCondition |
323 |
|
324 |
def __init__(self, lock): |
325 |
"""Initializes this class.
|
326 |
|
327 |
"""
|
328 |
_BaseCondition.__init__(self, lock)
|
329 |
self._waiters = set() |
330 |
self._single_condition = self._single_condition_class(self._lock) |
331 |
|
332 |
def wait(self, timeout): |
333 |
"""Wait for a notification.
|
334 |
|
335 |
@type timeout: float or None
|
336 |
@param timeout: Waiting timeout (can be None)
|
337 |
|
338 |
"""
|
339 |
self._check_owned()
|
340 |
|
341 |
# Keep local reference to the pipe. It could be replaced by another thread
|
342 |
# notifying while we're waiting.
|
343 |
cond = self._single_condition
|
344 |
|
345 |
self._waiters.add(threading.currentThread())
|
346 |
try:
|
347 |
cond.wait(timeout) |
348 |
finally:
|
349 |
self._check_owned()
|
350 |
self._waiters.remove(threading.currentThread())
|
351 |
|
352 |
def notifyAll(self): # pylint: disable=C0103 |
353 |
"""Notify all currently waiting threads.
|
354 |
|
355 |
"""
|
356 |
self._check_owned()
|
357 |
self._single_condition.notifyAll()
|
358 |
self._single_condition = self._single_condition_class(self._lock) |
359 |
|
360 |
def get_waiting(self): |
361 |
"""Returns a list of all waiting threads.
|
362 |
|
363 |
"""
|
364 |
self._check_owned()
|
365 |
|
366 |
return self._waiters |
367 |
|
368 |
def has_waiting(self): |
369 |
"""Returns whether there are active waiters.
|
370 |
|
371 |
"""
|
372 |
self._check_owned()
|
373 |
|
374 |
return bool(self._waiters) |
375 |
|
376 |
def __repr__(self): |
377 |
return ("<%s.%s waiters=%s at %#x>" % |
378 |
(self.__class__.__module__, self.__class__.__name__, |
379 |
self._waiters, id(self))) |
380 |
|
381 |
|
382 |
class _PipeConditionWithMode(PipeCondition): |
383 |
__slots__ = [ |
384 |
"shared",
|
385 |
] |
386 |
|
387 |
def __init__(self, lock, shared): |
388 |
"""Initializes this class.
|
389 |
|
390 |
"""
|
391 |
self.shared = shared
|
392 |
PipeCondition.__init__(self, lock)
|
393 |
|
394 |
|
395 |
class SharedLock(object): |
396 |
"""Implements a shared lock.
|
397 |
|
398 |
Multiple threads can acquire the lock in a shared way by calling
|
399 |
C{acquire(shared=1)}. In order to acquire the lock in an exclusive way
|
400 |
threads can call C{acquire(shared=0)}.
|
401 |
|
402 |
Notes on data structures: C{__pending} contains a priority queue (heapq) of
|
403 |
all pending acquires: C{[(priority1: prioqueue1), (priority2: prioqueue2),
|
404 |
...]}. Each per-priority queue contains a normal in-order list of conditions
|
405 |
to be notified when the lock can be acquired. Shared locks are grouped
|
406 |
together by priority and the condition for them is stored in
|
407 |
C{__pending_shared} if it already exists. C{__pending_by_prio} keeps
|
408 |
references for the per-priority queues indexed by priority for faster access.
|
409 |
|
410 |
@type name: string
|
411 |
@ivar name: the name of the lock
|
412 |
|
413 |
"""
|
414 |
__slots__ = [ |
415 |
"__weakref__",
|
416 |
"__deleted",
|
417 |
"__exc",
|
418 |
"__lock",
|
419 |
"__pending",
|
420 |
"__pending_by_prio",
|
421 |
"__pending_shared",
|
422 |
"__shr",
|
423 |
"__time_fn",
|
424 |
"name",
|
425 |
] |
426 |
|
427 |
__condition_class = _PipeConditionWithMode |
428 |
|
429 |
def __init__(self, name, monitor=None, _time_fn=time.time): |
430 |
"""Construct a new SharedLock.
|
431 |
|
432 |
@param name: the name of the lock
|
433 |
@type monitor: L{LockMonitor}
|
434 |
@param monitor: Lock monitor with which to register
|
435 |
|
436 |
"""
|
437 |
object.__init__(self) |
438 |
|
439 |
self.name = name
|
440 |
|
441 |
# Used for unittesting
|
442 |
self.__time_fn = _time_fn
|
443 |
|
444 |
# Internal lock
|
445 |
self.__lock = threading.Lock()
|
446 |
|
447 |
# Queue containing waiting acquires
|
448 |
self.__pending = []
|
449 |
self.__pending_by_prio = {}
|
450 |
self.__pending_shared = {}
|
451 |
|
452 |
# Current lock holders
|
453 |
self.__shr = set() |
454 |
self.__exc = None |
455 |
|
456 |
# is this lock in the deleted state?
|
457 |
self.__deleted = False |
458 |
|
459 |
# Register with lock monitor
|
460 |
if monitor:
|
461 |
logging.debug("Adding lock %s to monitor", name)
|
462 |
monitor.RegisterLock(self)
|
463 |
|
464 |
def __repr__(self): |
465 |
return ("<%s.%s name=%s at %#x>" % |
466 |
(self.__class__.__module__, self.__class__.__name__, |
467 |
self.name, id(self))) |
468 |
|
469 |
def GetLockInfo(self, requested): |
470 |
"""Retrieves information for querying locks.
|
471 |
|
472 |
@type requested: set
|
473 |
@param requested: Requested information, see C{query.LQ_*}
|
474 |
|
475 |
"""
|
476 |
self.__lock.acquire()
|
477 |
try:
|
478 |
# Note: to avoid unintentional race conditions, no references to
|
479 |
# modifiable objects should be returned unless they were created in this
|
480 |
# function.
|
481 |
mode = None
|
482 |
owner_names = None
|
483 |
|
484 |
if query.LQ_MODE in requested: |
485 |
if self.__deleted: |
486 |
mode = _DELETED_TEXT |
487 |
assert not (self.__exc or self.__shr) |
488 |
elif self.__exc: |
489 |
mode = _EXCLUSIVE_TEXT |
490 |
elif self.__shr: |
491 |
mode = _SHARED_TEXT |
492 |
|
493 |
# Current owner(s) are wanted
|
494 |
if query.LQ_OWNER in requested: |
495 |
if self.__exc: |
496 |
owner = [self.__exc]
|
497 |
else:
|
498 |
owner = self.__shr
|
499 |
|
500 |
if owner:
|
501 |
assert not self.__deleted |
502 |
owner_names = [i.getName() for i in owner] |
503 |
|
504 |
# Pending acquires are wanted
|
505 |
if query.LQ_PENDING in requested: |
506 |
pending = [] |
507 |
|
508 |
# Sorting instead of copying and using heaq functions for simplicity
|
509 |
for (_, prioqueue) in sorted(self.__pending): |
510 |
for cond in prioqueue: |
511 |
if cond.shared:
|
512 |
pendmode = _SHARED_TEXT |
513 |
else:
|
514 |
pendmode = _EXCLUSIVE_TEXT |
515 |
|
516 |
# List of names will be sorted in L{query._GetLockPending}
|
517 |
pending.append((pendmode, [i.getName() |
518 |
for i in cond.get_waiting()])) |
519 |
else:
|
520 |
pending = None
|
521 |
|
522 |
return [(self.name, mode, owner_names, pending)] |
523 |
finally:
|
524 |
self.__lock.release()
|
525 |
|
526 |
def __check_deleted(self): |
527 |
"""Raises an exception if the lock has been deleted.
|
528 |
|
529 |
"""
|
530 |
if self.__deleted: |
531 |
raise errors.LockError("Deleted lock %s" % self.name) |
532 |
|
533 |
def __is_sharer(self): |
534 |
"""Is the current thread sharing the lock at this time?
|
535 |
|
536 |
"""
|
537 |
return threading.currentThread() in self.__shr |
538 |
|
539 |
def __is_exclusive(self): |
540 |
"""Is the current thread holding the lock exclusively at this time?
|
541 |
|
542 |
"""
|
543 |
return threading.currentThread() == self.__exc |
544 |
|
545 |
def __is_owned(self, shared=-1): |
546 |
"""Is the current thread somehow owning the lock at this time?
|
547 |
|
548 |
This is a private version of the function, which presumes you're holding
|
549 |
the internal lock.
|
550 |
|
551 |
"""
|
552 |
if shared < 0: |
553 |
return self.__is_sharer() or self.__is_exclusive() |
554 |
elif shared:
|
555 |
return self.__is_sharer() |
556 |
else:
|
557 |
return self.__is_exclusive() |
558 |
|
559 |
def is_owned(self, shared=-1): |
560 |
"""Is the current thread somehow owning the lock at this time?
|
561 |
|
562 |
@param shared:
|
563 |
- < 0: check for any type of ownership (default)
|
564 |
- 0: check for exclusive ownership
|
565 |
- > 0: check for shared ownership
|
566 |
|
567 |
"""
|
568 |
self.__lock.acquire()
|
569 |
try:
|
570 |
return self.__is_owned(shared=shared) |
571 |
finally:
|
572 |
self.__lock.release()
|
573 |
|
574 |
#: Necessary to remain compatible with threading.Condition, which tries to
|
575 |
#: retrieve a locks' "_is_owned" attribute
|
576 |
_is_owned = is_owned |
577 |
|
578 |
def _count_pending(self): |
579 |
"""Returns the number of pending acquires.
|
580 |
|
581 |
@rtype: int
|
582 |
|
583 |
"""
|
584 |
self.__lock.acquire()
|
585 |
try:
|
586 |
return sum(len(prioqueue) for (_, prioqueue) in self.__pending) |
587 |
finally:
|
588 |
self.__lock.release()
|
589 |
|
590 |
def _check_empty(self): |
591 |
"""Checks whether there are any pending acquires.
|
592 |
|
593 |
@rtype: bool
|
594 |
|
595 |
"""
|
596 |
self.__lock.acquire()
|
597 |
try:
|
598 |
# Order is important: __find_first_pending_queue modifies __pending
|
599 |
(_, prioqueue) = self.__find_first_pending_queue()
|
600 |
|
601 |
return not (prioqueue or |
602 |
self.__pending or |
603 |
self.__pending_by_prio or |
604 |
self.__pending_shared)
|
605 |
finally:
|
606 |
self.__lock.release()
|
607 |
|
608 |
def __do_acquire(self, shared): |
609 |
"""Actually acquire the lock.
|
610 |
|
611 |
"""
|
612 |
if shared:
|
613 |
self.__shr.add(threading.currentThread())
|
614 |
else:
|
615 |
self.__exc = threading.currentThread()
|
616 |
|
617 |
def __can_acquire(self, shared): |
618 |
"""Determine whether lock can be acquired.
|
619 |
|
620 |
"""
|
621 |
if shared:
|
622 |
return self.__exc is None |
623 |
else:
|
624 |
return len(self.__shr) == 0 and self.__exc is None |
625 |
|
626 |
def __find_first_pending_queue(self): |
627 |
"""Tries to find the topmost queued entry with pending acquires.
|
628 |
|
629 |
Removes empty entries while going through the list.
|
630 |
|
631 |
"""
|
632 |
while self.__pending: |
633 |
(priority, prioqueue) = self.__pending[0] |
634 |
|
635 |
if prioqueue:
|
636 |
return (priority, prioqueue)
|
637 |
|
638 |
# Remove empty queue
|
639 |
heapq.heappop(self.__pending)
|
640 |
del self.__pending_by_prio[priority] |
641 |
assert priority not in self.__pending_shared |
642 |
|
643 |
return (None, None) |
644 |
|
645 |
def __is_on_top(self, cond): |
646 |
"""Checks whether the passed condition is on top of the queue.
|
647 |
|
648 |
The caller must make sure the queue isn't empty.
|
649 |
|
650 |
"""
|
651 |
(_, prioqueue) = self.__find_first_pending_queue()
|
652 |
|
653 |
return cond == prioqueue[0] |
654 |
|
655 |
def __acquire_unlocked(self, shared, timeout, priority): |
656 |
"""Acquire a shared lock.
|
657 |
|
658 |
@param shared: whether to acquire in shared mode; by default an
|
659 |
exclusive lock will be acquired
|
660 |
@param timeout: maximum waiting time before giving up
|
661 |
@type priority: integer
|
662 |
@param priority: Priority for acquiring lock
|
663 |
|
664 |
"""
|
665 |
self.__check_deleted()
|
666 |
|
667 |
# We cannot acquire the lock if we already have it
|
668 |
assert not self.__is_owned(), ("double acquire() on a non-recursive lock" |
669 |
" %s" % self.name) |
670 |
|
671 |
# Remove empty entries from queue
|
672 |
self.__find_first_pending_queue()
|
673 |
|
674 |
# Check whether someone else holds the lock or there are pending acquires.
|
675 |
if not self.__pending and self.__can_acquire(shared): |
676 |
# Apparently not, can acquire lock directly.
|
677 |
self.__do_acquire(shared)
|
678 |
return True |
679 |
|
680 |
# The lock couldn't be acquired right away, so if a timeout is given and is
|
681 |
# considered too short, return right away as scheduling a pending
|
682 |
# acquisition is quite expensive
|
683 |
if timeout is not None and timeout < _LOCK_ACQUIRE_MIN_TIMEOUT: |
684 |
return False |
685 |
|
686 |
prioqueue = self.__pending_by_prio.get(priority, None) |
687 |
|
688 |
if shared:
|
689 |
# Try to re-use condition for shared acquire
|
690 |
wait_condition = self.__pending_shared.get(priority, None) |
691 |
assert (wait_condition is None or |
692 |
(wait_condition.shared and wait_condition in prioqueue)) |
693 |
else:
|
694 |
wait_condition = None
|
695 |
|
696 |
if wait_condition is None: |
697 |
if prioqueue is None: |
698 |
assert priority not in self.__pending_by_prio |
699 |
|
700 |
prioqueue = [] |
701 |
heapq.heappush(self.__pending, (priority, prioqueue))
|
702 |
self.__pending_by_prio[priority] = prioqueue
|
703 |
|
704 |
wait_condition = self.__condition_class(self.__lock, shared) |
705 |
prioqueue.append(wait_condition) |
706 |
|
707 |
if shared:
|
708 |
# Keep reference for further shared acquires on same priority. This is
|
709 |
# better than trying to find it in the list of pending acquires.
|
710 |
assert priority not in self.__pending_shared |
711 |
self.__pending_shared[priority] = wait_condition
|
712 |
|
713 |
wait_start = self.__time_fn()
|
714 |
acquired = False
|
715 |
|
716 |
try:
|
717 |
# Wait until we become the topmost acquire in the queue or the timeout
|
718 |
# expires.
|
719 |
while True: |
720 |
if self.__is_on_top(wait_condition) and self.__can_acquire(shared): |
721 |
self.__do_acquire(shared)
|
722 |
acquired = True
|
723 |
break
|
724 |
|
725 |
# A lot of code assumes blocking acquires always succeed, therefore we
|
726 |
# can never return False for a blocking acquire
|
727 |
if (timeout is not None and |
728 |
utils.TimeoutExpired(wait_start, timeout, _time_fn=self.__time_fn)):
|
729 |
break
|
730 |
|
731 |
# Wait for notification
|
732 |
wait_condition.wait(timeout) |
733 |
self.__check_deleted()
|
734 |
finally:
|
735 |
# Remove condition from queue if there are no more waiters
|
736 |
if not wait_condition.has_waiting(): |
737 |
prioqueue.remove(wait_condition) |
738 |
if wait_condition.shared:
|
739 |
# Remove from list of shared acquires if it wasn't while releasing
|
740 |
# (e.g. on lock deletion)
|
741 |
self.__pending_shared.pop(priority, None) |
742 |
|
743 |
return acquired
|
744 |
|
745 |
def acquire(self, shared=0, timeout=None, priority=None, |
746 |
test_notify=None):
|
747 |
"""Acquire a shared lock.
|
748 |
|
749 |
@type shared: integer (0/1) used as a boolean
|
750 |
@param shared: whether to acquire in shared mode; by default an
|
751 |
exclusive lock will be acquired
|
752 |
@type timeout: float
|
753 |
@param timeout: maximum waiting time before giving up
|
754 |
@type priority: integer
|
755 |
@param priority: Priority for acquiring lock
|
756 |
@type test_notify: callable or None
|
757 |
@param test_notify: Special callback function for unittesting
|
758 |
|
759 |
"""
|
760 |
if priority is None: |
761 |
priority = _DEFAULT_PRIORITY |
762 |
|
763 |
self.__lock.acquire()
|
764 |
try:
|
765 |
# We already got the lock, notify now
|
766 |
if __debug__ and callable(test_notify): |
767 |
test_notify() |
768 |
|
769 |
return self.__acquire_unlocked(shared, timeout, priority) |
770 |
finally:
|
771 |
self.__lock.release()
|
772 |
|
773 |
def downgrade(self): |
774 |
"""Changes the lock mode from exclusive to shared.
|
775 |
|
776 |
Pending acquires in shared mode on the same priority will go ahead.
|
777 |
|
778 |
"""
|
779 |
self.__lock.acquire()
|
780 |
try:
|
781 |
assert self.__is_owned(), "Lock must be owned" |
782 |
|
783 |
if self.__is_exclusive(): |
784 |
# Do nothing if the lock is already acquired in shared mode
|
785 |
self.__exc = None |
786 |
self.__do_acquire(1) |
787 |
|
788 |
# Important: pending shared acquires should only jump ahead if there
|
789 |
# was a transition from exclusive to shared, otherwise an owner of a
|
790 |
# shared lock can keep calling this function to push incoming shared
|
791 |
# acquires
|
792 |
(priority, prioqueue) = self.__find_first_pending_queue()
|
793 |
if prioqueue:
|
794 |
# Is there a pending shared acquire on this priority?
|
795 |
cond = self.__pending_shared.pop(priority, None) |
796 |
if cond:
|
797 |
assert cond.shared
|
798 |
assert cond in prioqueue |
799 |
|
800 |
# Ensure shared acquire is on top of queue
|
801 |
if len(prioqueue) > 1: |
802 |
prioqueue.remove(cond) |
803 |
prioqueue.insert(0, cond)
|
804 |
|
805 |
# Notify
|
806 |
cond.notifyAll() |
807 |
|
808 |
assert not self.__is_exclusive() |
809 |
assert self.__is_sharer() |
810 |
|
811 |
return True |
812 |
finally:
|
813 |
self.__lock.release()
|
814 |
|
815 |
def release(self): |
816 |
"""Release a Shared Lock.
|
817 |
|
818 |
You must have acquired the lock, either in shared or in exclusive mode,
|
819 |
before calling this function.
|
820 |
|
821 |
"""
|
822 |
self.__lock.acquire()
|
823 |
try:
|
824 |
assert self.__is_exclusive() or self.__is_sharer(), \ |
825 |
"Cannot release non-owned lock"
|
826 |
|
827 |
# Autodetect release type
|
828 |
if self.__is_exclusive(): |
829 |
self.__exc = None |
830 |
notify = True
|
831 |
else:
|
832 |
self.__shr.remove(threading.currentThread())
|
833 |
notify = not self.__shr |
834 |
|
835 |
# Notify topmost condition in queue if there are no owners left (for
|
836 |
# shared locks)
|
837 |
if notify:
|
838 |
self.__notify_topmost()
|
839 |
finally:
|
840 |
self.__lock.release()
|
841 |
|
842 |
def __notify_topmost(self): |
843 |
"""Notifies topmost condition in queue of pending acquires.
|
844 |
|
845 |
"""
|
846 |
(priority, prioqueue) = self.__find_first_pending_queue()
|
847 |
if prioqueue:
|
848 |
cond = prioqueue[0]
|
849 |
cond.notifyAll() |
850 |
if cond.shared:
|
851 |
# Prevent further shared acquires from sneaking in while waiters are
|
852 |
# notified
|
853 |
self.__pending_shared.pop(priority, None) |
854 |
|
855 |
def _notify_topmost(self): |
856 |
"""Exported version of L{__notify_topmost}.
|
857 |
|
858 |
"""
|
859 |
self.__lock.acquire()
|
860 |
try:
|
861 |
return self.__notify_topmost() |
862 |
finally:
|
863 |
self.__lock.release()
|
864 |
|
865 |
def delete(self, timeout=None, priority=None): |
866 |
"""Delete a Shared Lock.
|
867 |
|
868 |
This operation will declare the lock for removal. First the lock will be
|
869 |
acquired in exclusive mode if you don't already own it, then the lock
|
870 |
will be put in a state where any future and pending acquire() fail.
|
871 |
|
872 |
@type timeout: float
|
873 |
@param timeout: maximum waiting time before giving up
|
874 |
@type priority: integer
|
875 |
@param priority: Priority for acquiring lock
|
876 |
|
877 |
"""
|
878 |
if priority is None: |
879 |
priority = _DEFAULT_PRIORITY |
880 |
|
881 |
self.__lock.acquire()
|
882 |
try:
|
883 |
assert not self.__is_sharer(), "Cannot delete() a lock while sharing it" |
884 |
|
885 |
self.__check_deleted()
|
886 |
|
887 |
# The caller is allowed to hold the lock exclusively already.
|
888 |
acquired = self.__is_exclusive()
|
889 |
|
890 |
if not acquired: |
891 |
acquired = self.__acquire_unlocked(0, timeout, priority) |
892 |
|
893 |
if acquired:
|
894 |
assert self.__is_exclusive() and not self.__is_sharer(), \ |
895 |
"Lock wasn't acquired in exclusive mode"
|
896 |
|
897 |
self.__deleted = True |
898 |
self.__exc = None |
899 |
|
900 |
assert not (self.__exc or self.__shr), "Found owner during deletion" |
901 |
|
902 |
# Notify all acquires. They'll throw an error.
|
903 |
for (_, prioqueue) in self.__pending: |
904 |
for cond in prioqueue: |
905 |
cond.notifyAll() |
906 |
|
907 |
assert self.__deleted |
908 |
|
909 |
return acquired
|
910 |
finally:
|
911 |
self.__lock.release()
|
912 |
|
913 |
def _release_save(self): |
914 |
shared = self.__is_sharer()
|
915 |
self.release()
|
916 |
return shared
|
917 |
|
918 |
def _acquire_restore(self, shared): |
919 |
self.acquire(shared=shared)
|
920 |
|
921 |
|
922 |
# Whenever we want to acquire a full LockSet we pass None as the value
|
923 |
# to acquire. Hide this behind this nicely named constant.
|
924 |
ALL_SET = None
|
925 |
|
926 |
|
927 |
def _TimeoutZero(): |
928 |
"""Returns the number zero.
|
929 |
|
930 |
"""
|
931 |
return 0 |
932 |
|
933 |
|
934 |
def _GetLsAcquireModeAndTimeouts(want_all, timeout, opportunistic): |
935 |
"""Determines modes and timeouts for L{LockSet.acquire}.
|
936 |
|
937 |
@type want_all: boolean
|
938 |
@param want_all: Whether all locks in set should be acquired
|
939 |
@param timeout: Timeout in seconds or C{None}
|
940 |
@param opportunistic: Whther locks should be acquired opportunistically
|
941 |
@rtype: tuple
|
942 |
@return: Tuple containing mode to be passed to L{LockSet.__acquire_inner}
|
943 |
(one of L{_LS_ACQUIRE_MODES}), a function to calculate timeout for
|
944 |
acquiring the lockset-internal lock (might be C{None}) and a function to
|
945 |
calculate the timeout for acquiring individual locks
|
946 |
|
947 |
"""
|
948 |
# Short circuit when no running timeout is needed
|
949 |
if opportunistic and not want_all: |
950 |
assert timeout is None, "Got timeout for an opportunistic acquisition" |
951 |
return (_LS_ACQUIRE_OPPORTUNISTIC, None, _TimeoutZero) |
952 |
|
953 |
# We need to keep track of how long we spent waiting for a lock. The
|
954 |
# timeout passed to this function is over all lock acquisitions.
|
955 |
running_timeout = utils.RunningTimeout(timeout, False)
|
956 |
|
957 |
if want_all:
|
958 |
mode = _LS_ACQUIRE_ALL |
959 |
ls_timeout_fn = running_timeout.Remaining |
960 |
else:
|
961 |
mode = _LS_ACQUIRE_EXACT |
962 |
ls_timeout_fn = None
|
963 |
|
964 |
if opportunistic:
|
965 |
mode = _LS_ACQUIRE_OPPORTUNISTIC |
966 |
timeout_fn = _TimeoutZero |
967 |
else:
|
968 |
timeout_fn = running_timeout.Remaining |
969 |
|
970 |
return (mode, ls_timeout_fn, timeout_fn)
|
971 |
|
972 |
|
973 |
class _AcquireTimeout(Exception): |
974 |
"""Internal exception to abort an acquire on a timeout.
|
975 |
|
976 |
"""
|
977 |
|
978 |
|
979 |
class LockSet: |
980 |
"""Implements a set of locks.
|
981 |
|
982 |
This abstraction implements a set of shared locks for the same resource type,
|
983 |
distinguished by name. The user can lock a subset of the resources and the
|
984 |
LockSet will take care of acquiring the locks always in the same order, thus
|
985 |
preventing deadlock.
|
986 |
|
987 |
All the locks needed in the same set must be acquired together, though.
|
988 |
|
989 |
@type name: string
|
990 |
@ivar name: the name of the lockset
|
991 |
|
992 |
"""
|
993 |
def __init__(self, members, name, monitor=None): |
994 |
"""Constructs a new LockSet.
|
995 |
|
996 |
@type members: list of strings
|
997 |
@param members: initial members of the set
|
998 |
@type monitor: L{LockMonitor}
|
999 |
@param monitor: Lock monitor with which to register member locks
|
1000 |
|
1001 |
"""
|
1002 |
assert members is not None, "members parameter is not a list" |
1003 |
self.name = name
|
1004 |
|
1005 |
# Lock monitor
|
1006 |
self.__monitor = monitor
|
1007 |
|
1008 |
# Used internally to guarantee coherency
|
1009 |
self.__lock = SharedLock(self._GetLockName("[lockset]"), monitor=monitor) |
1010 |
|
1011 |
# The lockdict indexes the relationship name -> lock
|
1012 |
# The order-of-locking is implied by the alphabetical order of names
|
1013 |
self.__lockdict = {}
|
1014 |
|
1015 |
for mname in members: |
1016 |
self.__lockdict[mname] = SharedLock(self._GetLockName(mname), |
1017 |
monitor=monitor) |
1018 |
|
1019 |
# The owner dict contains the set of locks each thread owns. For
|
1020 |
# performance each thread can access its own key without a global lock on
|
1021 |
# this structure. It is paramount though that *no* other type of access is
|
1022 |
# done to this structure (eg. no looping over its keys). *_owner helper
|
1023 |
# function are defined to guarantee access is correct, but in general never
|
1024 |
# do anything different than __owners[threading.currentThread()], or there
|
1025 |
# will be trouble.
|
1026 |
self.__owners = {}
|
1027 |
|
1028 |
def _GetLockName(self, mname): |
1029 |
"""Returns the name for a member lock.
|
1030 |
|
1031 |
"""
|
1032 |
return "%s/%s" % (self.name, mname) |
1033 |
|
1034 |
def _get_lock(self): |
1035 |
"""Returns the lockset-internal lock.
|
1036 |
|
1037 |
"""
|
1038 |
return self.__lock |
1039 |
|
1040 |
def _get_lockdict(self): |
1041 |
"""Returns the lockset-internal lock dictionary.
|
1042 |
|
1043 |
Accessing this structure is only safe in single-thread usage or when the
|
1044 |
lockset-internal lock is held.
|
1045 |
|
1046 |
"""
|
1047 |
return self.__lockdict |
1048 |
|
1049 |
def is_owned(self): |
1050 |
"""Is the current thread a current level owner?
|
1051 |
|
1052 |
@note: Use L{check_owned} to check if a specific lock is held
|
1053 |
|
1054 |
"""
|
1055 |
return threading.currentThread() in self.__owners |
1056 |
|
1057 |
def check_owned(self, names, shared=-1): |
1058 |
"""Check if locks are owned in a specific mode.
|
1059 |
|
1060 |
@type names: sequence or string
|
1061 |
@param names: Lock names (or a single lock name)
|
1062 |
@param shared: See L{SharedLock.is_owned}
|
1063 |
@rtype: bool
|
1064 |
@note: Use L{is_owned} to check if the current thread holds I{any} lock and
|
1065 |
L{list_owned} to get the names of all owned locks
|
1066 |
|
1067 |
"""
|
1068 |
if isinstance(names, basestring): |
1069 |
names = [names] |
1070 |
|
1071 |
# Avoid check if no locks are owned anyway
|
1072 |
if names and self.is_owned(): |
1073 |
candidates = [] |
1074 |
|
1075 |
# Gather references to all locks (in case they're deleted in the meantime)
|
1076 |
for lname in names: |
1077 |
try:
|
1078 |
lock = self.__lockdict[lname]
|
1079 |
except KeyError: |
1080 |
raise errors.LockError("Non-existing lock '%s' in set '%s' (it may" |
1081 |
" have been removed)" % (lname, self.name)) |
1082 |
else:
|
1083 |
candidates.append(lock) |
1084 |
|
1085 |
return compat.all(lock.is_owned(shared=shared) for lock in candidates) |
1086 |
else:
|
1087 |
return False |
1088 |
|
1089 |
def owning_all(self): |
1090 |
"""Checks whether current thread owns internal lock.
|
1091 |
|
1092 |
Holding the internal lock is equivalent with holding all locks in the set
|
1093 |
(the opposite does not necessarily hold as it can not be easily
|
1094 |
determined). L{add} and L{remove} require the internal lock.
|
1095 |
|
1096 |
@rtype: boolean
|
1097 |
|
1098 |
"""
|
1099 |
return self.__lock.is_owned() |
1100 |
|
1101 |
def _add_owned(self, name=None): |
1102 |
"""Note the current thread owns the given lock"""
|
1103 |
if name is None: |
1104 |
if not self.is_owned(): |
1105 |
self.__owners[threading.currentThread()] = set() |
1106 |
else:
|
1107 |
if self.is_owned(): |
1108 |
self.__owners[threading.currentThread()].add(name)
|
1109 |
else:
|
1110 |
self.__owners[threading.currentThread()] = set([name]) |
1111 |
|
1112 |
def _del_owned(self, name=None): |
1113 |
"""Note the current thread owns the given lock"""
|
1114 |
|
1115 |
assert not (name is None and self.__lock.is_owned()), \ |
1116 |
"Cannot hold internal lock when deleting owner status"
|
1117 |
|
1118 |
if name is not None: |
1119 |
self.__owners[threading.currentThread()].remove(name)
|
1120 |
|
1121 |
# Only remove the key if we don't hold the set-lock as well
|
1122 |
if not (self.__lock.is_owned() or |
1123 |
self.__owners[threading.currentThread()]):
|
1124 |
del self.__owners[threading.currentThread()] |
1125 |
|
1126 |
def list_owned(self): |
1127 |
"""Get the set of resource names owned by the current thread"""
|
1128 |
if self.is_owned(): |
1129 |
return self.__owners[threading.currentThread()].copy() |
1130 |
else:
|
1131 |
return set() |
1132 |
|
1133 |
def _release_and_delete_owned(self): |
1134 |
"""Release and delete all resources owned by the current thread"""
|
1135 |
for lname in self.list_owned(): |
1136 |
lock = self.__lockdict[lname]
|
1137 |
if lock.is_owned():
|
1138 |
lock.release() |
1139 |
self._del_owned(name=lname)
|
1140 |
|
1141 |
def __names(self): |
1142 |
"""Return the current set of names.
|
1143 |
|
1144 |
Only call this function while holding __lock and don't iterate on the
|
1145 |
result after releasing the lock.
|
1146 |
|
1147 |
"""
|
1148 |
return self.__lockdict.keys() |
1149 |
|
1150 |
def _names(self): |
1151 |
"""Return a copy of the current set of elements.
|
1152 |
|
1153 |
Used only for debugging purposes.
|
1154 |
|
1155 |
"""
|
1156 |
# If we don't already own the set-level lock acquired
|
1157 |
# we'll get it and note we need to release it later.
|
1158 |
release_lock = False
|
1159 |
if not self.__lock.is_owned(): |
1160 |
release_lock = True
|
1161 |
self.__lock.acquire(shared=1) |
1162 |
try:
|
1163 |
result = self.__names()
|
1164 |
finally:
|
1165 |
if release_lock:
|
1166 |
self.__lock.release()
|
1167 |
return set(result) |
1168 |
|
1169 |
def acquire(self, names, timeout=None, shared=0, priority=None, |
1170 |
opportunistic=False, test_notify=None): |
1171 |
"""Acquire a set of resource locks.
|
1172 |
|
1173 |
@note: When acquiring locks opportunistically, any number of locks might
|
1174 |
actually be acquired, even zero.
|
1175 |
|
1176 |
@type names: list of strings (or string)
|
1177 |
@param names: the names of the locks which shall be acquired
|
1178 |
(special lock names, or instance/node names)
|
1179 |
@type shared: integer (0/1) used as a boolean
|
1180 |
@param shared: whether to acquire in shared mode; by default an
|
1181 |
exclusive lock will be acquired
|
1182 |
@type timeout: float or None
|
1183 |
@param timeout: Maximum time to acquire all locks; for opportunistic
|
1184 |
acquisitions, a timeout can only be given when C{names} is C{None}, in
|
1185 |
which case it is exclusively used for acquiring the L{LockSet}-internal
|
1186 |
lock; opportunistic acquisitions don't use a timeout for acquiring
|
1187 |
individual locks
|
1188 |
@type priority: integer
|
1189 |
@param priority: Priority for acquiring locks
|
1190 |
@type opportunistic: boolean
|
1191 |
@param opportunistic: Acquire locks opportunistically; use the return value
|
1192 |
to determine which locks were actually acquired
|
1193 |
@type test_notify: callable or None
|
1194 |
@param test_notify: Special callback function for unittesting
|
1195 |
|
1196 |
@return: Set of all locks successfully acquired or None in case of timeout
|
1197 |
|
1198 |
@raise errors.LockError: when any lock we try to acquire has
|
1199 |
been deleted before we succeed. In this case none of the
|
1200 |
locks requested will be acquired.
|
1201 |
|
1202 |
"""
|
1203 |
assert timeout is None or timeout >= 0.0 |
1204 |
|
1205 |
# Check we don't already own locks at this level
|
1206 |
assert not self.is_owned(), ("Cannot acquire locks in the same set twice" |
1207 |
" (lockset %s)" % self.name) |
1208 |
|
1209 |
if priority is None: |
1210 |
priority = _DEFAULT_PRIORITY |
1211 |
|
1212 |
try:
|
1213 |
if names is not None: |
1214 |
assert timeout is None or not opportunistic, \ |
1215 |
("Opportunistic acquisitions can only use a timeout if no"
|
1216 |
" names are given; see docstring for details")
|
1217 |
|
1218 |
# Support passing in a single resource to acquire rather than many
|
1219 |
if isinstance(names, basestring): |
1220 |
names = [names] |
1221 |
|
1222 |
(mode, _, timeout_fn) = \ |
1223 |
_GetLsAcquireModeAndTimeouts(False, timeout, opportunistic)
|
1224 |
|
1225 |
return self.__acquire_inner(names, mode, shared, priority, |
1226 |
timeout_fn, test_notify) |
1227 |
|
1228 |
else:
|
1229 |
(mode, ls_timeout_fn, timeout_fn) = \ |
1230 |
_GetLsAcquireModeAndTimeouts(True, timeout, opportunistic)
|
1231 |
|
1232 |
# If no names are given acquire the whole set by not letting new names
|
1233 |
# being added before we release, and getting the current list of names.
|
1234 |
# Some of them may then be deleted later, but we'll cope with this.
|
1235 |
#
|
1236 |
# We'd like to acquire this lock in a shared way, as it's nice if
|
1237 |
# everybody else can use the instances at the same time. If we are
|
1238 |
# acquiring them exclusively though they won't be able to do this
|
1239 |
# anyway, though, so we'll get the list lock exclusively as well in
|
1240 |
# order to be able to do add() on the set while owning it.
|
1241 |
if not self.__lock.acquire(shared=shared, priority=priority, |
1242 |
timeout=ls_timeout_fn()): |
1243 |
raise _AcquireTimeout()
|
1244 |
|
1245 |
try:
|
1246 |
# note we own the set-lock
|
1247 |
self._add_owned()
|
1248 |
|
1249 |
return self.__acquire_inner(self.__names(), mode, shared, |
1250 |
priority, timeout_fn, test_notify) |
1251 |
except:
|
1252 |
# We shouldn't have problems adding the lock to the owners list, but
|
1253 |
# if we did we'll try to release this lock and re-raise exception.
|
1254 |
# Of course something is going to be really wrong, after this.
|
1255 |
self.__lock.release()
|
1256 |
self._del_owned()
|
1257 |
raise
|
1258 |
|
1259 |
except _AcquireTimeout:
|
1260 |
return None |
1261 |
|
1262 |
def __acquire_inner(self, names, mode, shared, priority, |
1263 |
timeout_fn, test_notify): |
1264 |
"""Inner logic for acquiring a number of locks.
|
1265 |
|
1266 |
Acquisition modes:
|
1267 |
|
1268 |
- C{_LS_ACQUIRE_ALL}: C{names} contains names of all locks in set, but
|
1269 |
deleted locks can be ignored as the whole set is being acquired with
|
1270 |
its internal lock held
|
1271 |
- C{_LS_ACQUIRE_EXACT}: The names listed in C{names} must be acquired;
|
1272 |
timeouts and deleted locks are fatal
|
1273 |
- C{_LS_ACQUIRE_OPPORTUNISTIC}: C{names} lists names of locks (potentially
|
1274 |
all within the set) which should be acquired opportunistically, that is
|
1275 |
failures are ignored
|
1276 |
|
1277 |
@param names: Names of the locks to be acquired
|
1278 |
@param mode: Lock acquisition mode (one of L{_LS_ACQUIRE_MODES})
|
1279 |
@param shared: Whether to acquire in shared mode
|
1280 |
@param timeout_fn: Function returning remaining timeout (C{None} for
|
1281 |
opportunistic acquisitions)
|
1282 |
@param priority: Priority for acquiring locks
|
1283 |
@param test_notify: Special callback function for unittesting
|
1284 |
|
1285 |
"""
|
1286 |
assert mode in _LS_ACQUIRE_MODES |
1287 |
|
1288 |
acquire_list = [] |
1289 |
|
1290 |
# First we look the locks up on __lockdict. We have no way of being sure
|
1291 |
# they will still be there after, but this makes it a lot faster should
|
1292 |
# just one of them be the already wrong. Using a sorted sequence to prevent
|
1293 |
# deadlocks.
|
1294 |
for lname in sorted(frozenset(names)): |
1295 |
try:
|
1296 |
lock = self.__lockdict[lname] # raises KeyError if lock is not there |
1297 |
except KeyError: |
1298 |
# We are acquiring the whole set, it doesn't matter if this particular
|
1299 |
# element is not there anymore. If, however, only certain names should
|
1300 |
# be acquired, not finding a lock is an error.
|
1301 |
if mode == _LS_ACQUIRE_EXACT:
|
1302 |
raise errors.LockError("Lock '%s' not found in set '%s' (it may have" |
1303 |
" been removed)" % (lname, self.name)) |
1304 |
else:
|
1305 |
acquire_list.append((lname, lock)) |
1306 |
|
1307 |
# This will hold the locknames we effectively acquired.
|
1308 |
acquired = set()
|
1309 |
|
1310 |
try:
|
1311 |
# Now acquire_list contains a sorted list of resources and locks we
|
1312 |
# want. In order to get them we loop on this (private) list and
|
1313 |
# acquire() them. We gave no real guarantee they will still exist till
|
1314 |
# this is done but .acquire() itself is safe and will alert us if the
|
1315 |
# lock gets deleted.
|
1316 |
for (lname, lock) in acquire_list: |
1317 |
if __debug__ and callable(test_notify): |
1318 |
test_notify_fn = lambda: test_notify(lname)
|
1319 |
else:
|
1320 |
test_notify_fn = None
|
1321 |
|
1322 |
timeout = timeout_fn() |
1323 |
|
1324 |
try:
|
1325 |
# raises LockError if the lock was deleted
|
1326 |
acq_success = lock.acquire(shared=shared, timeout=timeout, |
1327 |
priority=priority, |
1328 |
test_notify=test_notify_fn) |
1329 |
except errors.LockError:
|
1330 |
if mode in (_LS_ACQUIRE_ALL, _LS_ACQUIRE_OPPORTUNISTIC): |
1331 |
# We are acquiring the whole set, it doesn't matter if this
|
1332 |
# particular element is not there anymore.
|
1333 |
continue
|
1334 |
|
1335 |
raise errors.LockError("Lock '%s' not found in set '%s' (it may have" |
1336 |
" been removed)" % (lname, self.name)) |
1337 |
|
1338 |
if not acq_success: |
1339 |
# Couldn't get lock or timeout occurred
|
1340 |
if mode == _LS_ACQUIRE_OPPORTUNISTIC:
|
1341 |
# Ignore timeouts on opportunistic acquisitions
|
1342 |
continue
|
1343 |
|
1344 |
if timeout is None: |
1345 |
# This shouldn't happen as SharedLock.acquire(timeout=None) is
|
1346 |
# blocking.
|
1347 |
raise errors.LockError("Failed to get lock %s (set %s)" % |
1348 |
(lname, self.name))
|
1349 |
|
1350 |
raise _AcquireTimeout()
|
1351 |
|
1352 |
try:
|
1353 |
# now the lock cannot be deleted, we have it!
|
1354 |
self._add_owned(name=lname)
|
1355 |
acquired.add(lname) |
1356 |
|
1357 |
except:
|
1358 |
# We shouldn't have problems adding the lock to the owners list, but
|
1359 |
# if we did we'll try to release this lock and re-raise exception.
|
1360 |
# Of course something is going to be really wrong after this.
|
1361 |
if lock.is_owned():
|
1362 |
lock.release() |
1363 |
raise
|
1364 |
|
1365 |
except:
|
1366 |
# Release all owned locks
|
1367 |
self._release_and_delete_owned()
|
1368 |
raise
|
1369 |
|
1370 |
return acquired
|
1371 |
|
1372 |
def downgrade(self, names=None): |
1373 |
"""Downgrade a set of resource locks from exclusive to shared mode.
|
1374 |
|
1375 |
The locks must have been acquired in exclusive mode.
|
1376 |
|
1377 |
"""
|
1378 |
assert self.is_owned(), ("downgrade on lockset %s while not owning any" |
1379 |
" lock" % self.name) |
1380 |
|
1381 |
# Support passing in a single resource to downgrade rather than many
|
1382 |
if isinstance(names, basestring): |
1383 |
names = [names] |
1384 |
|
1385 |
owned = self.list_owned()
|
1386 |
|
1387 |
if names is None: |
1388 |
names = owned |
1389 |
else:
|
1390 |
names = set(names)
|
1391 |
assert owned.issuperset(names), \
|
1392 |
("downgrade() on unheld resources %s (set %s)" %
|
1393 |
(names.difference(owned), self.name))
|
1394 |
|
1395 |
for lockname in names: |
1396 |
self.__lockdict[lockname].downgrade()
|
1397 |
|
1398 |
# Do we own the lockset in exclusive mode?
|
1399 |
if self.__lock.is_owned(shared=0): |
1400 |
# Have all locks been downgraded?
|
1401 |
if not compat.any(lock.is_owned(shared=0) |
1402 |
for lock in self.__lockdict.values()): |
1403 |
self.__lock.downgrade()
|
1404 |
assert self.__lock.is_owned(shared=1) |
1405 |
|
1406 |
return True |
1407 |
|
1408 |
def release(self, names=None): |
1409 |
"""Release a set of resource locks, at the same level.
|
1410 |
|
1411 |
You must have acquired the locks, either in shared or in exclusive mode,
|
1412 |
before releasing them.
|
1413 |
|
1414 |
@type names: list of strings, or None
|
1415 |
@param names: the names of the locks which shall be released
|
1416 |
(defaults to all the locks acquired at that level).
|
1417 |
|
1418 |
"""
|
1419 |
assert self.is_owned(), ("release() on lock set %s while not owner" % |
1420 |
self.name)
|
1421 |
|
1422 |
# Support passing in a single resource to release rather than many
|
1423 |
if isinstance(names, basestring): |
1424 |
names = [names] |
1425 |
|
1426 |
if names is None: |
1427 |
names = self.list_owned()
|
1428 |
else:
|
1429 |
names = set(names)
|
1430 |
assert self.list_owned().issuperset(names), ( |
1431 |
"release() on unheld resources %s (set %s)" %
|
1432 |
(names.difference(self.list_owned()), self.name)) |
1433 |
|
1434 |
# First of all let's release the "all elements" lock, if set.
|
1435 |
# After this 'add' can work again
|
1436 |
if self.__lock.is_owned(): |
1437 |
self.__lock.release()
|
1438 |
self._del_owned()
|
1439 |
|
1440 |
for lockname in names: |
1441 |
# If we are sure the lock doesn't leave __lockdict without being
|
1442 |
# exclusively held we can do this...
|
1443 |
self.__lockdict[lockname].release()
|
1444 |
self._del_owned(name=lockname)
|
1445 |
|
1446 |
def add(self, names, acquired=0, shared=0): |
1447 |
"""Add a new set of elements to the set
|
1448 |
|
1449 |
@type names: list of strings
|
1450 |
@param names: names of the new elements to add
|
1451 |
@type acquired: integer (0/1) used as a boolean
|
1452 |
@param acquired: pre-acquire the new resource?
|
1453 |
@type shared: integer (0/1) used as a boolean
|
1454 |
@param shared: is the pre-acquisition shared?
|
1455 |
|
1456 |
"""
|
1457 |
# Check we don't already own locks at this level
|
1458 |
assert not self.is_owned() or self.__lock.is_owned(shared=0), \ |
1459 |
("Cannot add locks if the set %s is only partially owned, or shared" %
|
1460 |
self.name)
|
1461 |
|
1462 |
# Support passing in a single resource to add rather than many
|
1463 |
if isinstance(names, basestring): |
1464 |
names = [names] |
1465 |
|
1466 |
# If we don't already own the set-level lock acquired in an exclusive way
|
1467 |
# we'll get it and note we need to release it later.
|
1468 |
release_lock = False
|
1469 |
if not self.__lock.is_owned(): |
1470 |
release_lock = True
|
1471 |
self.__lock.acquire()
|
1472 |
|
1473 |
try:
|
1474 |
invalid_names = set(self.__names()).intersection(names) |
1475 |
if invalid_names:
|
1476 |
# This must be an explicit raise, not an assert, because assert is
|
1477 |
# turned off when using optimization, and this can happen because of
|
1478 |
# concurrency even if the user doesn't want it.
|
1479 |
raise errors.LockError("duplicate add(%s) on lockset %s" % |
1480 |
(invalid_names, self.name))
|
1481 |
|
1482 |
for lockname in names: |
1483 |
lock = SharedLock(self._GetLockName(lockname), monitor=self.__monitor) |
1484 |
|
1485 |
if acquired:
|
1486 |
# No need for priority or timeout here as this lock has just been
|
1487 |
# created
|
1488 |
lock.acquire(shared=shared) |
1489 |
# now the lock cannot be deleted, we have it!
|
1490 |
try:
|
1491 |
self._add_owned(name=lockname)
|
1492 |
except:
|
1493 |
# We shouldn't have problems adding the lock to the owners list,
|
1494 |
# but if we did we'll try to release this lock and re-raise
|
1495 |
# exception. Of course something is going to be really wrong,
|
1496 |
# after this. On the other hand the lock hasn't been added to the
|
1497 |
# __lockdict yet so no other threads should be pending on it. This
|
1498 |
# release is just a safety measure.
|
1499 |
lock.release() |
1500 |
raise
|
1501 |
|
1502 |
self.__lockdict[lockname] = lock
|
1503 |
|
1504 |
finally:
|
1505 |
# Only release __lock if we were not holding it previously.
|
1506 |
if release_lock:
|
1507 |
self.__lock.release()
|
1508 |
|
1509 |
return True |
1510 |
|
1511 |
def remove(self, names): |
1512 |
"""Remove elements from the lock set.
|
1513 |
|
1514 |
You can either not hold anything in the lockset or already hold a superset
|
1515 |
of the elements you want to delete, exclusively.
|
1516 |
|
1517 |
@type names: list of strings
|
1518 |
@param names: names of the resource to remove.
|
1519 |
|
1520 |
@return: a list of locks which we removed; the list is always
|
1521 |
equal to the names list if we were holding all the locks
|
1522 |
exclusively
|
1523 |
|
1524 |
"""
|
1525 |
# Support passing in a single resource to remove rather than many
|
1526 |
if isinstance(names, basestring): |
1527 |
names = [names] |
1528 |
|
1529 |
# If we own any subset of this lock it must be a superset of what we want
|
1530 |
# to delete. The ownership must also be exclusive, but that will be checked
|
1531 |
# by the lock itself.
|
1532 |
assert not self.is_owned() or self.list_owned().issuperset(names), ( |
1533 |
"remove() on acquired lockset %s while not owning all elements" %
|
1534 |
self.name)
|
1535 |
|
1536 |
removed = [] |
1537 |
|
1538 |
for lname in names: |
1539 |
# Calling delete() acquires the lock exclusively if we don't already own
|
1540 |
# it, and causes all pending and subsequent lock acquires to fail. It's
|
1541 |
# fine to call it out of order because delete() also implies release(),
|
1542 |
# and the assertion above guarantees that if we either already hold
|
1543 |
# everything we want to delete, or we hold none.
|
1544 |
try:
|
1545 |
self.__lockdict[lname].delete()
|
1546 |
removed.append(lname) |
1547 |
except (KeyError, errors.LockError): |
1548 |
# This cannot happen if we were already holding it, verify:
|
1549 |
assert not self.is_owned(), ("remove failed while holding lockset %s" % |
1550 |
self.name)
|
1551 |
else:
|
1552 |
# If no LockError was raised we are the ones who deleted the lock.
|
1553 |
# This means we can safely remove it from lockdict, as any further or
|
1554 |
# pending delete() or acquire() will fail (and nobody can have the lock
|
1555 |
# since before our call to delete()).
|
1556 |
#
|
1557 |
# This is done in an else clause because if the exception was thrown
|
1558 |
# it's the job of the one who actually deleted it.
|
1559 |
del self.__lockdict[lname] |
1560 |
# And let's remove it from our private list if we owned it.
|
1561 |
if self.is_owned(): |
1562 |
self._del_owned(name=lname)
|
1563 |
|
1564 |
return removed
|
1565 |
|
1566 |
|
1567 |
# Locking levels, must be acquired in increasing order. Current rules are:
|
1568 |
# - At level LEVEL_CLUSTER resides the Big Ganeti Lock (BGL) which must be
|
1569 |
# acquired before performing any operation, either in shared or exclusive
|
1570 |
# mode. Acquiring the BGL in exclusive mode is discouraged and should be
|
1571 |
# avoided..
|
1572 |
# - At levels LEVEL_NODE and LEVEL_INSTANCE reside node and instance locks. If
|
1573 |
# you need more than one node, or more than one instance, acquire them at the
|
1574 |
# same time.
|
1575 |
# - LEVEL_NODE_RES is for node resources and should be used by operations with
|
1576 |
# possibly high impact on the node's disks.
|
1577 |
# - LEVEL_NODE_ALLOC blocks instance allocations for the whole cluster
|
1578 |
# ("NAL" is the only lock at this level). It should be acquired in shared
|
1579 |
# mode when an opcode blocks all or a significant amount of a cluster's
|
1580 |
# locks. Opcodes doing instance allocations should acquire in exclusive mode.
|
1581 |
# Once the set of acquired locks for an opcode has been reduced to the working
|
1582 |
# set, the NAL should be released as well to allow allocations to proceed.
|
1583 |
(LEVEL_CLUSTER, |
1584 |
LEVEL_INSTANCE, |
1585 |
LEVEL_NODE_ALLOC, |
1586 |
LEVEL_NODEGROUP, |
1587 |
LEVEL_NODE, |
1588 |
LEVEL_NODE_RES, |
1589 |
LEVEL_NETWORK) = range(0, 7) |
1590 |
|
1591 |
LEVELS = [ |
1592 |
LEVEL_CLUSTER, |
1593 |
LEVEL_INSTANCE, |
1594 |
LEVEL_NODE_ALLOC, |
1595 |
LEVEL_NODEGROUP, |
1596 |
LEVEL_NODE, |
1597 |
LEVEL_NODE_RES, |
1598 |
LEVEL_NETWORK, |
1599 |
] |
1600 |
|
1601 |
# Lock levels which are modifiable
|
1602 |
LEVELS_MOD = compat.UniqueFrozenset([ |
1603 |
LEVEL_NODE_RES, |
1604 |
LEVEL_NODE, |
1605 |
LEVEL_NODEGROUP, |
1606 |
LEVEL_INSTANCE, |
1607 |
LEVEL_NETWORK, |
1608 |
]) |
1609 |
|
1610 |
#: Lock level names (make sure to use singular form)
|
1611 |
LEVEL_NAMES = { |
1612 |
LEVEL_CLUSTER: "cluster",
|
1613 |
LEVEL_INSTANCE: "instance",
|
1614 |
LEVEL_NODE_ALLOC: "node-alloc",
|
1615 |
LEVEL_NODEGROUP: "nodegroup",
|
1616 |
LEVEL_NODE: "node",
|
1617 |
LEVEL_NODE_RES: "node-res",
|
1618 |
LEVEL_NETWORK: "network",
|
1619 |
} |
1620 |
|
1621 |
# Constant for the big ganeti lock
|
1622 |
BGL = "BGL"
|
1623 |
|
1624 |
#: Node allocation lock
|
1625 |
NAL = "NAL"
|
1626 |
|
1627 |
|
1628 |
class GanetiLockManager(object): |
1629 |
"""The Ganeti Locking Library
|
1630 |
|
1631 |
The purpose of this small library is to manage locking for ganeti clusters
|
1632 |
in a central place, while at the same time doing dynamic checks against
|
1633 |
possible deadlocks. It will also make it easier to transition to a different
|
1634 |
lock type should we migrate away from python threads.
|
1635 |
|
1636 |
"""
|
1637 |
_instance = None
|
1638 |
|
1639 |
def __init__(self, node_uuids, nodegroups, instance_names, networks): |
1640 |
"""Constructs a new GanetiLockManager object.
|
1641 |
|
1642 |
There should be only a GanetiLockManager object at any time, so this
|
1643 |
function raises an error if this is not the case.
|
1644 |
|
1645 |
@param node_uuids: list of node UUIDs
|
1646 |
@param nodegroups: list of nodegroup uuids
|
1647 |
@param instance_names: list of instance names
|
1648 |
|
1649 |
"""
|
1650 |
assert self.__class__._instance is None, \ |
1651 |
"double GanetiLockManager instance"
|
1652 |
|
1653 |
self.__class__._instance = self |
1654 |
|
1655 |
self._monitor = LockMonitor()
|
1656 |
|
1657 |
# The keyring contains all the locks, at their level and in the correct
|
1658 |
# locking order.
|
1659 |
self.__keyring = {
|
1660 |
LEVEL_CLUSTER: LockSet([BGL], "cluster", monitor=self._monitor), |
1661 |
LEVEL_NODE: LockSet(node_uuids, "node", monitor=self._monitor), |
1662 |
LEVEL_NODE_RES: LockSet(node_uuids, "node-res", monitor=self._monitor), |
1663 |
LEVEL_NODEGROUP: LockSet(nodegroups, "nodegroup", monitor=self._monitor), |
1664 |
LEVEL_INSTANCE: LockSet(instance_names, "instance",
|
1665 |
monitor=self._monitor),
|
1666 |
LEVEL_NETWORK: LockSet(networks, "network", monitor=self._monitor), |
1667 |
LEVEL_NODE_ALLOC: LockSet([NAL], "node-alloc", monitor=self._monitor), |
1668 |
} |
1669 |
|
1670 |
assert compat.all(ls.name == LEVEL_NAMES[level]
|
1671 |
for (level, ls) in self.__keyring.items()), \ |
1672 |
"Keyring name mismatch"
|
1673 |
|
1674 |
def AddToLockMonitor(self, provider): |
1675 |
"""Registers a new lock with the monitor.
|
1676 |
|
1677 |
See L{LockMonitor.RegisterLock}.
|
1678 |
|
1679 |
"""
|
1680 |
return self._monitor.RegisterLock(provider) |
1681 |
|
1682 |
def QueryLocks(self, fields): |
1683 |
"""Queries information from all locks.
|
1684 |
|
1685 |
See L{LockMonitor.QueryLocks}.
|
1686 |
|
1687 |
"""
|
1688 |
return self._monitor.QueryLocks(fields) |
1689 |
|
1690 |
def _names(self, level): |
1691 |
"""List the lock names at the given level.
|
1692 |
|
1693 |
This can be used for debugging/testing purposes.
|
1694 |
|
1695 |
@param level: the level whose list of locks to get
|
1696 |
|
1697 |
"""
|
1698 |
assert level in LEVELS, "Invalid locking level %s" % level |
1699 |
return self.__keyring[level]._names() |
1700 |
|
1701 |
def is_owned(self, level): |
1702 |
"""Check whether we are owning locks at the given level
|
1703 |
|
1704 |
"""
|
1705 |
return self.__keyring[level].is_owned() |
1706 |
|
1707 |
def list_owned(self, level): |
1708 |
"""Get the set of owned locks at the given level
|
1709 |
|
1710 |
"""
|
1711 |
return self.__keyring[level].list_owned() |
1712 |
|
1713 |
def check_owned(self, level, names, shared=-1): |
1714 |
"""Check if locks at a certain level are owned in a specific mode.
|
1715 |
|
1716 |
@see: L{LockSet.check_owned}
|
1717 |
|
1718 |
"""
|
1719 |
return self.__keyring[level].check_owned(names, shared=shared) |
1720 |
|
1721 |
def owning_all(self, level): |
1722 |
"""Checks whether current thread owns all locks at a certain level.
|
1723 |
|
1724 |
@see: L{LockSet.owning_all}
|
1725 |
|
1726 |
"""
|
1727 |
return self.__keyring[level].owning_all() |
1728 |
|
1729 |
def _upper_owned(self, level): |
1730 |
"""Check that we don't own any lock at a level greater than the given one.
|
1731 |
|
1732 |
"""
|
1733 |
# This way of checking only works if LEVELS[i] = i, which we check for in
|
1734 |
# the test cases.
|
1735 |
return compat.any((self.is_owned(l) for l in LEVELS[level + 1:])) |
1736 |
|
1737 |
def _BGL_owned(self): # pylint: disable=C0103 |
1738 |
"""Check if the current thread owns the BGL.
|
1739 |
|
1740 |
Both an exclusive or a shared acquisition work.
|
1741 |
|
1742 |
"""
|
1743 |
return BGL in self.__keyring[LEVEL_CLUSTER].list_owned() |
1744 |
|
1745 |
@staticmethod
|
1746 |
def _contains_BGL(level, names): # pylint: disable=C0103 |
1747 |
"""Check if the level contains the BGL.
|
1748 |
|
1749 |
Check if acting on the given level and set of names will change
|
1750 |
the status of the Big Ganeti Lock.
|
1751 |
|
1752 |
"""
|
1753 |
return level == LEVEL_CLUSTER and (names is None or BGL in names) |
1754 |
|
1755 |
def acquire(self, level, names, timeout=None, shared=0, priority=None, |
1756 |
opportunistic=False):
|
1757 |
"""Acquire a set of resource locks, at the same level.
|
1758 |
|
1759 |
@type level: member of locking.LEVELS
|
1760 |
@param level: the level at which the locks shall be acquired
|
1761 |
@type names: list of strings (or string)
|
1762 |
@param names: the names of the locks which shall be acquired
|
1763 |
(special lock names, or instance/node names)
|
1764 |
@type shared: integer (0/1) used as a boolean
|
1765 |
@param shared: whether to acquire in shared mode; by default
|
1766 |
an exclusive lock will be acquired
|
1767 |
@type timeout: float
|
1768 |
@param timeout: Maximum time to acquire all locks
|
1769 |
@type priority: integer
|
1770 |
@param priority: Priority for acquiring lock
|
1771 |
@type opportunistic: boolean
|
1772 |
@param opportunistic: Acquire locks opportunistically; use the return value
|
1773 |
to determine which locks were actually acquired
|
1774 |
|
1775 |
"""
|
1776 |
assert level in LEVELS, "Invalid locking level %s" % level |
1777 |
|
1778 |
# Check that we are either acquiring the Big Ganeti Lock or we already own
|
1779 |
# it. Some "legacy" opcodes need to be sure they are run non-concurrently
|
1780 |
# so even if we've migrated we need to at least share the BGL to be
|
1781 |
# compatible with them. Of course if we own the BGL exclusively there's no
|
1782 |
# point in acquiring any other lock, unless perhaps we are half way through
|
1783 |
# the migration of the current opcode.
|
1784 |
assert (self._contains_BGL(level, names) or self._BGL_owned()), ( |
1785 |
"You must own the Big Ganeti Lock before acquiring any other")
|
1786 |
|
1787 |
# Check we don't own locks at the same or upper levels.
|
1788 |
assert not self._upper_owned(level), ("Cannot acquire locks at a level" |
1789 |
" while owning some at a greater one")
|
1790 |
|
1791 |
# Acquire the locks in the set.
|
1792 |
return self.__keyring[level].acquire(names, shared=shared, timeout=timeout, |
1793 |
priority=priority, |
1794 |
opportunistic=opportunistic) |
1795 |
|
1796 |
def downgrade(self, level, names=None): |
1797 |
"""Downgrade a set of resource locks from exclusive to shared mode.
|
1798 |
|
1799 |
You must have acquired the locks in exclusive mode.
|
1800 |
|
1801 |
@type level: member of locking.LEVELS
|
1802 |
@param level: the level at which the locks shall be downgraded
|
1803 |
@type names: list of strings, or None
|
1804 |
@param names: the names of the locks which shall be downgraded
|
1805 |
(defaults to all the locks acquired at the level)
|
1806 |
|
1807 |
"""
|
1808 |
assert level in LEVELS, "Invalid locking level %s" % level |
1809 |
|
1810 |
return self.__keyring[level].downgrade(names=names) |
1811 |
|
1812 |
def release(self, level, names=None): |
1813 |
"""Release a set of resource locks, at the same level.
|
1814 |
|
1815 |
You must have acquired the locks, either in shared or in exclusive
|
1816 |
mode, before releasing them.
|
1817 |
|
1818 |
@type level: member of locking.LEVELS
|
1819 |
@param level: the level at which the locks shall be released
|
1820 |
@type names: list of strings, or None
|
1821 |
@param names: the names of the locks which shall be released
|
1822 |
(defaults to all the locks acquired at that level)
|
1823 |
|
1824 |
"""
|
1825 |
assert level in LEVELS, "Invalid locking level %s" % level |
1826 |
assert (not self._contains_BGL(level, names) or |
1827 |
not self._upper_owned(LEVEL_CLUSTER)), ( |
1828 |
"Cannot release the Big Ganeti Lock while holding something"
|
1829 |
" at upper levels (%r)" %
|
1830 |
(utils.CommaJoin(["%s=%r" % (LEVEL_NAMES[i], self.list_owned(i)) |
1831 |
for i in self.__keyring.keys()]), )) |
1832 |
|
1833 |
# Release will complain if we don't own the locks already
|
1834 |
return self.__keyring[level].release(names) |
1835 |
|
1836 |
def add(self, level, names, acquired=0, shared=0): |
1837 |
"""Add locks at the specified level.
|
1838 |
|
1839 |
@type level: member of locking.LEVELS_MOD
|
1840 |
@param level: the level at which the locks shall be added
|
1841 |
@type names: list of strings
|
1842 |
@param names: names of the locks to acquire
|
1843 |
@type acquired: integer (0/1) used as a boolean
|
1844 |
@param acquired: whether to acquire the newly added locks
|
1845 |
@type shared: integer (0/1) used as a boolean
|
1846 |
@param shared: whether the acquisition will be shared
|
1847 |
|
1848 |
"""
|
1849 |
assert level in LEVELS_MOD, "Invalid or immutable level %s" % level |
1850 |
assert self._BGL_owned(), ("You must own the BGL before performing other" |
1851 |
" operations")
|
1852 |
assert not self._upper_owned(level), ("Cannot add locks at a level" |
1853 |
" while owning some at a greater one")
|
1854 |
return self.__keyring[level].add(names, acquired=acquired, shared=shared) |
1855 |
|
1856 |
def remove(self, level, names): |
1857 |
"""Remove locks from the specified level.
|
1858 |
|
1859 |
You must either already own the locks you are trying to remove
|
1860 |
exclusively or not own any lock at an upper level.
|
1861 |
|
1862 |
@type level: member of locking.LEVELS_MOD
|
1863 |
@param level: the level at which the locks shall be removed
|
1864 |
@type names: list of strings
|
1865 |
@param names: the names of the locks which shall be removed
|
1866 |
(special lock names, or instance/node names)
|
1867 |
|
1868 |
"""
|
1869 |
assert level in LEVELS_MOD, "Invalid or immutable level %s" % level |
1870 |
assert self._BGL_owned(), ("You must own the BGL before performing other" |
1871 |
" operations")
|
1872 |
# Check we either own the level or don't own anything from here
|
1873 |
# up. LockSet.remove() will check the case in which we don't own
|
1874 |
# all the needed resources, or we have a shared ownership.
|
1875 |
assert self.is_owned(level) or not self._upper_owned(level), ( |
1876 |
"Cannot remove locks at a level while not owning it or"
|
1877 |
" owning some at a greater one")
|
1878 |
return self.__keyring[level].remove(names) |
1879 |
|
1880 |
|
1881 |
def _MonitorSortKey((item, idx, num)): |
1882 |
"""Sorting key function.
|
1883 |
|
1884 |
Sort by name, registration order and then order of information. This provides
|
1885 |
a stable sort order over different providers, even if they return the same
|
1886 |
name.
|
1887 |
|
1888 |
"""
|
1889 |
(name, _, _, _) = item |
1890 |
|
1891 |
return (utils.NiceSortKey(name), num, idx)
|
1892 |
|
1893 |
|
1894 |
class LockMonitor(object): |
1895 |
_LOCK_ATTR = "_lock"
|
1896 |
|
1897 |
def __init__(self): |
1898 |
"""Initializes this class.
|
1899 |
|
1900 |
"""
|
1901 |
self._lock = SharedLock("LockMonitor") |
1902 |
|
1903 |
# Counter for stable sorting
|
1904 |
self._counter = itertools.count(0) |
1905 |
|
1906 |
# Tracked locks. Weak references are used to avoid issues with circular
|
1907 |
# references and deletion.
|
1908 |
self._locks = weakref.WeakKeyDictionary()
|
1909 |
|
1910 |
@ssynchronized(_LOCK_ATTR)
|
1911 |
def RegisterLock(self, provider): |
1912 |
"""Registers a new lock.
|
1913 |
|
1914 |
@param provider: Object with a callable method named C{GetLockInfo}, taking
|
1915 |
a single C{set} containing the requested information items
|
1916 |
@note: It would be nicer to only receive the function generating the
|
1917 |
requested information but, as it turns out, weak references to bound
|
1918 |
methods (e.g. C{self.GetLockInfo}) are tricky; there are several
|
1919 |
workarounds, but none of the ones I found works properly in combination
|
1920 |
with a standard C{WeakKeyDictionary}
|
1921 |
|
1922 |
"""
|
1923 |
assert provider not in self._locks, "Duplicate registration" |
1924 |
|
1925 |
# There used to be a check for duplicate names here. As it turned out, when
|
1926 |
# a lock is re-created with the same name in a very short timeframe, the
|
1927 |
# previous instance might not yet be removed from the weakref dictionary.
|
1928 |
# By keeping track of the order of incoming registrations, a stable sort
|
1929 |
# ordering can still be guaranteed.
|
1930 |
|
1931 |
self._locks[provider] = self._counter.next() |
1932 |
|
1933 |
def _GetLockInfo(self, requested): |
1934 |
"""Get information from all locks.
|
1935 |
|
1936 |
"""
|
1937 |
# Must hold lock while getting consistent list of tracked items
|
1938 |
self._lock.acquire(shared=1) |
1939 |
try:
|
1940 |
items = self._locks.items()
|
1941 |
finally:
|
1942 |
self._lock.release()
|
1943 |
|
1944 |
return [(info, idx, num)
|
1945 |
for (provider, num) in items |
1946 |
for (idx, info) in enumerate(provider.GetLockInfo(requested))] |
1947 |
|
1948 |
def _Query(self, fields): |
1949 |
"""Queries information from all locks.
|
1950 |
|
1951 |
@type fields: list of strings
|
1952 |
@param fields: List of fields to return
|
1953 |
|
1954 |
"""
|
1955 |
qobj = query.Query(query.LOCK_FIELDS, fields) |
1956 |
|
1957 |
# Get all data with internal lock held and then sort by name and incoming
|
1958 |
# order
|
1959 |
lockinfo = sorted(self._GetLockInfo(qobj.RequestedData()), |
1960 |
key=_MonitorSortKey) |
1961 |
|
1962 |
# Extract lock information and build query data
|
1963 |
return (qobj, query.LockQueryData(map(compat.fst, lockinfo))) |
1964 |
|
1965 |
def QueryLocks(self, fields): |
1966 |
"""Queries information from all locks.
|
1967 |
|
1968 |
@type fields: list of strings
|
1969 |
@param fields: List of fields to return
|
1970 |
|
1971 |
"""
|
1972 |
(qobj, ctx) = self._Query(fields)
|
1973 |
|
1974 |
# Prepare query response
|
1975 |
return query.GetQueryResponse(qobj, ctx)
|