root / lib / locking.py @ 84e344d4
History | View | Annotate | Download (30.1 kB)
1 | 162c1c1f | Guido Trotter | #
|
---|---|---|---|
2 | 162c1c1f | Guido Trotter | #
|
3 | 162c1c1f | Guido Trotter | |
4 | 162c1c1f | Guido Trotter | # Copyright (C) 2006, 2007 Google Inc.
|
5 | 162c1c1f | Guido Trotter | #
|
6 | 162c1c1f | Guido Trotter | # This program is free software; you can redistribute it and/or modify
|
7 | 162c1c1f | Guido Trotter | # it under the terms of the GNU General Public License as published by
|
8 | 162c1c1f | Guido Trotter | # the Free Software Foundation; either version 2 of the License, or
|
9 | 162c1c1f | Guido Trotter | # (at your option) any later version.
|
10 | 162c1c1f | Guido Trotter | #
|
11 | 162c1c1f | Guido Trotter | # This program is distributed in the hope that it will be useful, but
|
12 | 162c1c1f | Guido Trotter | # WITHOUT ANY WARRANTY; without even the implied warranty of
|
13 | 162c1c1f | Guido Trotter | # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
14 | 162c1c1f | Guido Trotter | # General Public License for more details.
|
15 | 162c1c1f | Guido Trotter | #
|
16 | 162c1c1f | Guido Trotter | # You should have received a copy of the GNU General Public License
|
17 | 162c1c1f | Guido Trotter | # along with this program; if not, write to the Free Software
|
18 | 162c1c1f | Guido Trotter | # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
|
19 | 162c1c1f | Guido Trotter | # 02110-1301, USA.
|
20 | 162c1c1f | Guido Trotter | |
21 | 162c1c1f | Guido Trotter | """Module implementing the Ganeti locking code."""
|
22 | 162c1c1f | Guido Trotter | |
23 | 162c1c1f | Guido Trotter | import threading |
24 | 84e344d4 | Michael Hanselmann | |
25 | a95fd5d7 | Guido Trotter | from ganeti import errors |
26 | 7ee7c0c7 | Guido Trotter | from ganeti import utils |
27 | 162c1c1f | Guido Trotter | |
28 | 162c1c1f | Guido Trotter | |
29 | 42a999d1 | Guido Trotter | def ssynchronized(lock, shared=0): |
30 | 42a999d1 | Guido Trotter | """Shared Synchronization decorator.
|
31 | 42a999d1 | Guido Trotter |
|
32 | 42a999d1 | Guido Trotter | Calls the function holding the given lock, either in exclusive or shared
|
33 | 42a999d1 | Guido Trotter | mode. It requires the passed lock to be a SharedLock (or support its
|
34 | 42a999d1 | Guido Trotter | semantics).
|
35 | 42a999d1 | Guido Trotter |
|
36 | 42a999d1 | Guido Trotter | """
|
37 | 42a999d1 | Guido Trotter | def wrap(fn): |
38 | 42a999d1 | Guido Trotter | def sync_function(*args, **kwargs): |
39 | 42a999d1 | Guido Trotter | lock.acquire(shared=shared) |
40 | 42a999d1 | Guido Trotter | try:
|
41 | 42a999d1 | Guido Trotter | return fn(*args, **kwargs)
|
42 | 42a999d1 | Guido Trotter | finally:
|
43 | 42a999d1 | Guido Trotter | lock.release() |
44 | 42a999d1 | Guido Trotter | return sync_function
|
45 | 42a999d1 | Guido Trotter | return wrap
|
46 | 42a999d1 | Guido Trotter | |
47 | 42a999d1 | Guido Trotter | |
48 | 84e344d4 | Michael Hanselmann | class _CountingCondition(object): |
49 | 84e344d4 | Michael Hanselmann | """Wrapper for Python's built-in threading.Condition class.
|
50 | 84e344d4 | Michael Hanselmann |
|
51 | 84e344d4 | Michael Hanselmann | This wrapper keeps a count of active waiters. We can't access the internal
|
52 | 84e344d4 | Michael Hanselmann | "__waiters" attribute of threading.Condition because it's not thread-safe.
|
53 | 84e344d4 | Michael Hanselmann |
|
54 | 84e344d4 | Michael Hanselmann | """
|
55 | 84e344d4 | Michael Hanselmann | __slots__ = [ |
56 | 84e344d4 | Michael Hanselmann | "_cond",
|
57 | 84e344d4 | Michael Hanselmann | "_nwaiters",
|
58 | 84e344d4 | Michael Hanselmann | ] |
59 | 84e344d4 | Michael Hanselmann | |
60 | 84e344d4 | Michael Hanselmann | def __init__(self, lock): |
61 | 84e344d4 | Michael Hanselmann | """Initializes this class.
|
62 | 84e344d4 | Michael Hanselmann |
|
63 | 84e344d4 | Michael Hanselmann | """
|
64 | 84e344d4 | Michael Hanselmann | object.__init__(self) |
65 | 84e344d4 | Michael Hanselmann | self._cond = threading.Condition(lock=lock)
|
66 | 84e344d4 | Michael Hanselmann | self._nwaiters = 0 |
67 | 84e344d4 | Michael Hanselmann | |
68 | 84e344d4 | Michael Hanselmann | def notifyAll(self): |
69 | 84e344d4 | Michael Hanselmann | """Notifies the condition.
|
70 | 84e344d4 | Michael Hanselmann |
|
71 | 84e344d4 | Michael Hanselmann | """
|
72 | 84e344d4 | Michael Hanselmann | return self._cond.notifyAll() |
73 | 84e344d4 | Michael Hanselmann | |
74 | 84e344d4 | Michael Hanselmann | def wait(self, timeout=None): |
75 | 84e344d4 | Michael Hanselmann | """Waits for the condition to be notified.
|
76 | 84e344d4 | Michael Hanselmann |
|
77 | 84e344d4 | Michael Hanselmann | @type timeout: float or None
|
78 | 84e344d4 | Michael Hanselmann | @param timeout: Timeout in seconds
|
79 | 84e344d4 | Michael Hanselmann |
|
80 | 84e344d4 | Michael Hanselmann | """
|
81 | 84e344d4 | Michael Hanselmann | assert self._nwaiters >= 0 |
82 | 84e344d4 | Michael Hanselmann | |
83 | 84e344d4 | Michael Hanselmann | self._nwaiters += 1 |
84 | 84e344d4 | Michael Hanselmann | try:
|
85 | 84e344d4 | Michael Hanselmann | return self._cond.wait(timeout=timeout) |
86 | 84e344d4 | Michael Hanselmann | finally:
|
87 | 84e344d4 | Michael Hanselmann | self._nwaiters -= 1 |
88 | 84e344d4 | Michael Hanselmann | |
89 | 84e344d4 | Michael Hanselmann | def has_waiting(self): |
90 | 84e344d4 | Michael Hanselmann | """Returns whether there are active waiters.
|
91 | 84e344d4 | Michael Hanselmann |
|
92 | 84e344d4 | Michael Hanselmann | """
|
93 | 84e344d4 | Michael Hanselmann | return bool(self._nwaiters) |
94 | 84e344d4 | Michael Hanselmann | |
95 | 84e344d4 | Michael Hanselmann | |
96 | 84e344d4 | Michael Hanselmann | class SharedLock(object): |
97 | 162c1c1f | Guido Trotter | """Implements a shared lock.
|
98 | 162c1c1f | Guido Trotter |
|
99 | 162c1c1f | Guido Trotter | Multiple threads can acquire the lock in a shared way, calling
|
100 | 162c1c1f | Guido Trotter | acquire_shared(). In order to acquire the lock in an exclusive way threads
|
101 | 162c1c1f | Guido Trotter | can call acquire_exclusive().
|
102 | 162c1c1f | Guido Trotter |
|
103 | 162c1c1f | Guido Trotter | The lock prevents starvation but does not guarantee that threads will acquire
|
104 | 162c1c1f | Guido Trotter | the shared lock in the order they queued for it, just that they will
|
105 | 162c1c1f | Guido Trotter | eventually do so.
|
106 | 162c1c1f | Guido Trotter |
|
107 | 162c1c1f | Guido Trotter | """
|
108 | 84e344d4 | Michael Hanselmann | __slots__ = [ |
109 | 84e344d4 | Michael Hanselmann | "__active_shr_c",
|
110 | 84e344d4 | Michael Hanselmann | "__inactive_shr_c",
|
111 | 84e344d4 | Michael Hanselmann | "__deleted",
|
112 | 84e344d4 | Michael Hanselmann | "__exc",
|
113 | 84e344d4 | Michael Hanselmann | "__lock",
|
114 | 84e344d4 | Michael Hanselmann | "__pending",
|
115 | 84e344d4 | Michael Hanselmann | "__shr",
|
116 | 84e344d4 | Michael Hanselmann | ] |
117 | 84e344d4 | Michael Hanselmann | |
118 | 84e344d4 | Michael Hanselmann | __condition_class = _CountingCondition |
119 | 84e344d4 | Michael Hanselmann | |
120 | 162c1c1f | Guido Trotter | def __init__(self): |
121 | 84e344d4 | Michael Hanselmann | """Construct a new SharedLock.
|
122 | 84e344d4 | Michael Hanselmann |
|
123 | 84e344d4 | Michael Hanselmann | """
|
124 | 84e344d4 | Michael Hanselmann | object.__init__(self) |
125 | 84e344d4 | Michael Hanselmann | |
126 | 84e344d4 | Michael Hanselmann | # Internal lock
|
127 | 162c1c1f | Guido Trotter | self.__lock = threading.Lock()
|
128 | 162c1c1f | Guido Trotter | |
129 | 84e344d4 | Michael Hanselmann | # Queue containing waiting acquires
|
130 | 84e344d4 | Michael Hanselmann | self.__pending = []
|
131 | 84e344d4 | Michael Hanselmann | |
132 | 84e344d4 | Michael Hanselmann | # Active and inactive conditions for shared locks
|
133 | 84e344d4 | Michael Hanselmann | self.__active_shr_c = self.__condition_class(self.__lock) |
134 | 84e344d4 | Michael Hanselmann | self.__inactive_shr_c = self.__condition_class(self.__lock) |
135 | 84e344d4 | Michael Hanselmann | |
136 | 84e344d4 | Michael Hanselmann | # Current lock holders
|
137 | 162c1c1f | Guido Trotter | self.__shr = set() |
138 | 162c1c1f | Guido Trotter | self.__exc = None |
139 | 162c1c1f | Guido Trotter | |
140 | a95fd5d7 | Guido Trotter | # is this lock in the deleted state?
|
141 | a95fd5d7 | Guido Trotter | self.__deleted = False |
142 | a95fd5d7 | Guido Trotter | |
143 | 84e344d4 | Michael Hanselmann | def __check_deleted(self): |
144 | 84e344d4 | Michael Hanselmann | """Raises an exception if the lock has been deleted.
|
145 | 84e344d4 | Michael Hanselmann |
|
146 | 84e344d4 | Michael Hanselmann | """
|
147 | 84e344d4 | Michael Hanselmann | if self.__deleted: |
148 | 84e344d4 | Michael Hanselmann | raise errors.LockError("Deleted lock") |
149 | 84e344d4 | Michael Hanselmann | |
150 | 162c1c1f | Guido Trotter | def __is_sharer(self): |
151 | 84e344d4 | Michael Hanselmann | """Is the current thread sharing the lock at this time?
|
152 | 84e344d4 | Michael Hanselmann |
|
153 | 84e344d4 | Michael Hanselmann | """
|
154 | 162c1c1f | Guido Trotter | return threading.currentThread() in self.__shr |
155 | 162c1c1f | Guido Trotter | |
156 | 162c1c1f | Guido Trotter | def __is_exclusive(self): |
157 | 84e344d4 | Michael Hanselmann | """Is the current thread holding the lock exclusively at this time?
|
158 | 84e344d4 | Michael Hanselmann |
|
159 | 84e344d4 | Michael Hanselmann | """
|
160 | 162c1c1f | Guido Trotter | return threading.currentThread() == self.__exc |
161 | 162c1c1f | Guido Trotter | |
162 | 162c1c1f | Guido Trotter | def __is_owned(self, shared=-1): |
163 | 162c1c1f | Guido Trotter | """Is the current thread somehow owning the lock at this time?
|
164 | 162c1c1f | Guido Trotter |
|
165 | 162c1c1f | Guido Trotter | This is a private version of the function, which presumes you're holding
|
166 | 162c1c1f | Guido Trotter | the internal lock.
|
167 | 162c1c1f | Guido Trotter |
|
168 | 162c1c1f | Guido Trotter | """
|
169 | 162c1c1f | Guido Trotter | if shared < 0: |
170 | 162c1c1f | Guido Trotter | return self.__is_sharer() or self.__is_exclusive() |
171 | 162c1c1f | Guido Trotter | elif shared:
|
172 | 162c1c1f | Guido Trotter | return self.__is_sharer() |
173 | 162c1c1f | Guido Trotter | else:
|
174 | 162c1c1f | Guido Trotter | return self.__is_exclusive() |
175 | 162c1c1f | Guido Trotter | |
176 | 162c1c1f | Guido Trotter | def _is_owned(self, shared=-1): |
177 | 162c1c1f | Guido Trotter | """Is the current thread somehow owning the lock at this time?
|
178 | 162c1c1f | Guido Trotter |
|
179 | c41eea6e | Iustin Pop | @param shared:
|
180 | c41eea6e | Iustin Pop | - < 0: check for any type of ownership (default)
|
181 | c41eea6e | Iustin Pop | - 0: check for exclusive ownership
|
182 | c41eea6e | Iustin Pop | - > 0: check for shared ownership
|
183 | 162c1c1f | Guido Trotter |
|
184 | 162c1c1f | Guido Trotter | """
|
185 | 162c1c1f | Guido Trotter | self.__lock.acquire()
|
186 | 162c1c1f | Guido Trotter | try:
|
187 | 84e344d4 | Michael Hanselmann | return self.__is_owned(shared=shared) |
188 | 162c1c1f | Guido Trotter | finally:
|
189 | 162c1c1f | Guido Trotter | self.__lock.release()
|
190 | 162c1c1f | Guido Trotter | |
191 | 84e344d4 | Michael Hanselmann | def _count_pending(self): |
192 | 84e344d4 | Michael Hanselmann | """Returns the number of pending acquires.
|
193 | a95fd5d7 | Guido Trotter |
|
194 | 84e344d4 | Michael Hanselmann | @rtype: int
|
195 | a95fd5d7 | Guido Trotter |
|
196 | a95fd5d7 | Guido Trotter | """
|
197 | 84e344d4 | Michael Hanselmann | self.__lock.acquire()
|
198 | 84e344d4 | Michael Hanselmann | try:
|
199 | 84e344d4 | Michael Hanselmann | return len(self.__pending) |
200 | 84e344d4 | Michael Hanselmann | finally:
|
201 | 84e344d4 | Michael Hanselmann | self.__lock.release()
|
202 | a95fd5d7 | Guido Trotter | |
203 | 84e344d4 | Michael Hanselmann | def __do_acquire(self, shared): |
204 | 84e344d4 | Michael Hanselmann | """Actually acquire the lock.
|
205 | 84e344d4 | Michael Hanselmann |
|
206 | 84e344d4 | Michael Hanselmann | """
|
207 | 84e344d4 | Michael Hanselmann | if shared:
|
208 | 84e344d4 | Michael Hanselmann | self.__shr.add(threading.currentThread())
|
209 | 84e344d4 | Michael Hanselmann | else:
|
210 | 84e344d4 | Michael Hanselmann | self.__exc = threading.currentThread()
|
211 | a95fd5d7 | Guido Trotter | |
212 | 84e344d4 | Michael Hanselmann | def __can_acquire(self, shared): |
213 | 84e344d4 | Michael Hanselmann | """Determine whether lock can be acquired.
|
214 | a95fd5d7 | Guido Trotter |
|
215 | a95fd5d7 | Guido Trotter | """
|
216 | 84e344d4 | Michael Hanselmann | if shared:
|
217 | 84e344d4 | Michael Hanselmann | return self.__exc is None |
218 | 84e344d4 | Michael Hanselmann | else:
|
219 | 84e344d4 | Michael Hanselmann | return len(self.__shr) == 0 and self.__exc is None |
220 | a95fd5d7 | Guido Trotter | |
221 | 84e344d4 | Michael Hanselmann | def __is_on_top(self, cond): |
222 | 84e344d4 | Michael Hanselmann | """Checks whether the passed condition is on top of the queue.
|
223 | a95fd5d7 | Guido Trotter |
|
224 | 84e344d4 | Michael Hanselmann | The caller must make sure the queue isn't empty.
|
225 | a95fd5d7 | Guido Trotter |
|
226 | 84e344d4 | Michael Hanselmann | """
|
227 | 84e344d4 | Michael Hanselmann | return self.__pending[0] == cond |
228 | 4d686df8 | Guido Trotter | |
229 | 84e344d4 | Michael Hanselmann | def __acquire_unlocked(self, shared=0, timeout=None): |
230 | 84e344d4 | Michael Hanselmann | """Acquire a shared lock.
|
231 | 9216a9f7 | Michael Hanselmann |
|
232 | 84e344d4 | Michael Hanselmann | @param shared: whether to acquire in shared mode; by default an
|
233 | 84e344d4 | Michael Hanselmann | exclusive lock will be acquired
|
234 | 84e344d4 | Michael Hanselmann | @param timeout: maximum waiting time before giving up
|
235 | 9216a9f7 | Michael Hanselmann |
|
236 | 9216a9f7 | Michael Hanselmann | """
|
237 | 84e344d4 | Michael Hanselmann | self.__check_deleted()
|
238 | 9216a9f7 | Michael Hanselmann | |
239 | 84e344d4 | Michael Hanselmann | # We cannot acquire the lock if we already have it
|
240 | 84e344d4 | Michael Hanselmann | assert not self.__is_owned(), "double acquire() on a non-recursive lock" |
241 | 84e344d4 | Michael Hanselmann | |
242 | 84e344d4 | Michael Hanselmann | # Check whether someone else holds the lock or there are pending acquires.
|
243 | 84e344d4 | Michael Hanselmann | if not self.__pending and self.__can_acquire(shared): |
244 | 84e344d4 | Michael Hanselmann | # Apparently not, can acquire lock directly.
|
245 | 84e344d4 | Michael Hanselmann | self.__do_acquire(shared)
|
246 | 84e344d4 | Michael Hanselmann | return True |
247 | 9216a9f7 | Michael Hanselmann | |
248 | 84e344d4 | Michael Hanselmann | if shared:
|
249 | 84e344d4 | Michael Hanselmann | wait_condition = self.__active_shr_c
|
250 | 9216a9f7 | Michael Hanselmann | |
251 | 84e344d4 | Michael Hanselmann | # Check if we're not yet in the queue
|
252 | 84e344d4 | Michael Hanselmann | if wait_condition not in self.__pending: |
253 | 84e344d4 | Michael Hanselmann | self.__pending.append(wait_condition)
|
254 | 84e344d4 | Michael Hanselmann | else:
|
255 | 84e344d4 | Michael Hanselmann | wait_condition = self.__condition_class(self.__lock) |
256 | 84e344d4 | Michael Hanselmann | # Always add to queue
|
257 | 84e344d4 | Michael Hanselmann | self.__pending.append(wait_condition)
|
258 | 84e344d4 | Michael Hanselmann | |
259 | 84e344d4 | Michael Hanselmann | try:
|
260 | 84e344d4 | Michael Hanselmann | # Wait until we become the topmost acquire in the queue or the timeout
|
261 | 84e344d4 | Michael Hanselmann | # expires.
|
262 | 84e344d4 | Michael Hanselmann | while not (self.__is_on_top(wait_condition) and |
263 | 84e344d4 | Michael Hanselmann | self.__can_acquire(shared)):
|
264 | 84e344d4 | Michael Hanselmann | # Wait for notification
|
265 | 84e344d4 | Michael Hanselmann | wait_condition.wait(timeout) |
266 | 84e344d4 | Michael Hanselmann | self.__check_deleted()
|
267 | 84e344d4 | Michael Hanselmann | |
268 | 84e344d4 | Michael Hanselmann | # A lot of code assumes blocking acquires always succeed. Loop
|
269 | 84e344d4 | Michael Hanselmann | # internally for that case.
|
270 | 84e344d4 | Michael Hanselmann | if timeout is not None: |
271 | 84e344d4 | Michael Hanselmann | break
|
272 | 84e344d4 | Michael Hanselmann | |
273 | 84e344d4 | Michael Hanselmann | if self.__is_on_top(wait_condition) and self.__can_acquire(shared): |
274 | 84e344d4 | Michael Hanselmann | self.__do_acquire(shared)
|
275 | 84e344d4 | Michael Hanselmann | return True |
276 | 9216a9f7 | Michael Hanselmann | finally:
|
277 | 84e344d4 | Michael Hanselmann | # Remove condition from queue if there are no more waiters
|
278 | 84e344d4 | Michael Hanselmann | if not wait_condition.has_waiting() and not self.__deleted: |
279 | 84e344d4 | Michael Hanselmann | self.__pending.remove(wait_condition)
|
280 | 9216a9f7 | Michael Hanselmann | |
281 | 84e344d4 | Michael Hanselmann | return False |
282 | 9216a9f7 | Michael Hanselmann | |
283 | 84e344d4 | Michael Hanselmann | def acquire(self, shared=0, timeout=None): |
284 | 162c1c1f | Guido Trotter | """Acquire a shared lock.
|
285 | 162c1c1f | Guido Trotter |
|
286 | 84e344d4 | Michael Hanselmann | @type shared: int
|
287 | c41eea6e | Iustin Pop | @param shared: whether to acquire in shared mode; by default an
|
288 | c41eea6e | Iustin Pop | exclusive lock will be acquired
|
289 | 84e344d4 | Michael Hanselmann | @type timeout: float
|
290 | 84e344d4 | Michael Hanselmann | @param timeout: maximum waiting time before giving up
|
291 | 162c1c1f | Guido Trotter |
|
292 | 162c1c1f | Guido Trotter | """
|
293 | 162c1c1f | Guido Trotter | self.__lock.acquire()
|
294 | 162c1c1f | Guido Trotter | try:
|
295 | 84e344d4 | Michael Hanselmann | return self.__acquire_unlocked(shared, timeout) |
296 | 162c1c1f | Guido Trotter | finally:
|
297 | 162c1c1f | Guido Trotter | self.__lock.release()
|
298 | 162c1c1f | Guido Trotter | |
299 | 162c1c1f | Guido Trotter | def release(self): |
300 | 162c1c1f | Guido Trotter | """Release a Shared Lock.
|
301 | 162c1c1f | Guido Trotter |
|
302 | 162c1c1f | Guido Trotter | You must have acquired the lock, either in shared or in exclusive mode,
|
303 | 162c1c1f | Guido Trotter | before calling this function.
|
304 | 162c1c1f | Guido Trotter |
|
305 | 162c1c1f | Guido Trotter | """
|
306 | 162c1c1f | Guido Trotter | self.__lock.acquire()
|
307 | 162c1c1f | Guido Trotter | try:
|
308 | 84e344d4 | Michael Hanselmann | assert self.__is_exclusive() or self.__is_sharer(), \ |
309 | 84e344d4 | Michael Hanselmann | "Cannot release non-owned lock"
|
310 | 84e344d4 | Michael Hanselmann | |
311 | 162c1c1f | Guido Trotter | # Autodetect release type
|
312 | 162c1c1f | Guido Trotter | if self.__is_exclusive(): |
313 | 162c1c1f | Guido Trotter | self.__exc = None |
314 | 84e344d4 | Michael Hanselmann | else:
|
315 | 162c1c1f | Guido Trotter | self.__shr.remove(threading.currentThread())
|
316 | 162c1c1f | Guido Trotter | |
317 | 84e344d4 | Michael Hanselmann | # Notify topmost condition in queue
|
318 | 84e344d4 | Michael Hanselmann | if self.__pending: |
319 | 84e344d4 | Michael Hanselmann | first_condition = self.__pending[0] |
320 | 84e344d4 | Michael Hanselmann | first_condition.notifyAll() |
321 | 4d686df8 | Guido Trotter | |
322 | 84e344d4 | Michael Hanselmann | if first_condition == self.__active_shr_c: |
323 | 84e344d4 | Michael Hanselmann | self.__active_shr_c = self.__inactive_shr_c |
324 | 84e344d4 | Michael Hanselmann | self.__inactive_shr_c = first_condition
|
325 | 162c1c1f | Guido Trotter | |
326 | 162c1c1f | Guido Trotter | finally:
|
327 | 162c1c1f | Guido Trotter | self.__lock.release()
|
328 | 162c1c1f | Guido Trotter | |
329 | 84e344d4 | Michael Hanselmann | def delete(self, timeout=None): |
330 | a95fd5d7 | Guido Trotter | """Delete a Shared Lock.
|
331 | a95fd5d7 | Guido Trotter |
|
332 | a95fd5d7 | Guido Trotter | This operation will declare the lock for removal. First the lock will be
|
333 | a95fd5d7 | Guido Trotter | acquired in exclusive mode if you don't already own it, then the lock
|
334 | a95fd5d7 | Guido Trotter | will be put in a state where any future and pending acquire() fail.
|
335 | a95fd5d7 | Guido Trotter |
|
336 | 84e344d4 | Michael Hanselmann | @type timeout: float
|
337 | 84e344d4 | Michael Hanselmann | @param timeout: maximum waiting time before giving up
|
338 | a95fd5d7 | Guido Trotter |
|
339 | a95fd5d7 | Guido Trotter | """
|
340 | a95fd5d7 | Guido Trotter | self.__lock.acquire()
|
341 | a95fd5d7 | Guido Trotter | try:
|
342 | 84e344d4 | Michael Hanselmann | assert not self.__is_sharer(), "Cannot delete() a lock while sharing it" |
343 | 84e344d4 | Michael Hanselmann | |
344 | 84e344d4 | Michael Hanselmann | self.__check_deleted()
|
345 | a95fd5d7 | Guido Trotter | |
346 | 84e344d4 | Michael Hanselmann | # The caller is allowed to hold the lock exclusively already.
|
347 | 84e344d4 | Michael Hanselmann | acquired = self.__is_exclusive()
|
348 | a95fd5d7 | Guido Trotter | |
349 | 84e344d4 | Michael Hanselmann | if not acquired: |
350 | 84e344d4 | Michael Hanselmann | acquired = self.__acquire_unlocked(timeout)
|
351 | 84e344d4 | Michael Hanselmann | |
352 | 84e344d4 | Michael Hanselmann | if acquired:
|
353 | 84e344d4 | Michael Hanselmann | self.__deleted = True |
354 | 84e344d4 | Michael Hanselmann | self.__exc = None |
355 | a95fd5d7 | Guido Trotter | |
356 | 84e344d4 | Michael Hanselmann | # Notify all acquires. They'll throw an error.
|
357 | 84e344d4 | Michael Hanselmann | while self.__pending: |
358 | 84e344d4 | Michael Hanselmann | self.__pending.pop().notifyAll()
|
359 | a95fd5d7 | Guido Trotter | |
360 | 84e344d4 | Michael Hanselmann | return acquired
|
361 | a95fd5d7 | Guido Trotter | finally:
|
362 | a95fd5d7 | Guido Trotter | self.__lock.release()
|
363 | a95fd5d7 | Guido Trotter | |
364 | aaae9bc0 | Guido Trotter | |
365 | f12eadb3 | Iustin Pop | # Whenever we want to acquire a full LockSet we pass None as the value
|
366 | 5bbd3f7f | Michael Hanselmann | # to acquire. Hide this behind this nicely named constant.
|
367 | e310b019 | Guido Trotter | ALL_SET = None
|
368 | e310b019 | Guido Trotter | |
369 | e310b019 | Guido Trotter | |
370 | aaae9bc0 | Guido Trotter | class LockSet: |
371 | aaae9bc0 | Guido Trotter | """Implements a set of locks.
|
372 | aaae9bc0 | Guido Trotter |
|
373 | aaae9bc0 | Guido Trotter | This abstraction implements a set of shared locks for the same resource type,
|
374 | aaae9bc0 | Guido Trotter | distinguished by name. The user can lock a subset of the resources and the
|
375 | aaae9bc0 | Guido Trotter | LockSet will take care of acquiring the locks always in the same order, thus
|
376 | aaae9bc0 | Guido Trotter | preventing deadlock.
|
377 | aaae9bc0 | Guido Trotter |
|
378 | aaae9bc0 | Guido Trotter | All the locks needed in the same set must be acquired together, though.
|
379 | aaae9bc0 | Guido Trotter |
|
380 | aaae9bc0 | Guido Trotter | """
|
381 | aaae9bc0 | Guido Trotter | def __init__(self, members=None): |
382 | aaae9bc0 | Guido Trotter | """Constructs a new LockSet.
|
383 | aaae9bc0 | Guido Trotter |
|
384 | c41eea6e | Iustin Pop | @param members: initial members of the set
|
385 | aaae9bc0 | Guido Trotter |
|
386 | aaae9bc0 | Guido Trotter | """
|
387 | aaae9bc0 | Guido Trotter | # Used internally to guarantee coherency.
|
388 | aaae9bc0 | Guido Trotter | self.__lock = SharedLock()
|
389 | aaae9bc0 | Guido Trotter | |
390 | aaae9bc0 | Guido Trotter | # The lockdict indexes the relationship name -> lock
|
391 | aaae9bc0 | Guido Trotter | # The order-of-locking is implied by the alphabetical order of names
|
392 | aaae9bc0 | Guido Trotter | self.__lockdict = {}
|
393 | aaae9bc0 | Guido Trotter | |
394 | aaae9bc0 | Guido Trotter | if members is not None: |
395 | aaae9bc0 | Guido Trotter | for name in members: |
396 | aaae9bc0 | Guido Trotter | self.__lockdict[name] = SharedLock()
|
397 | aaae9bc0 | Guido Trotter | |
398 | aaae9bc0 | Guido Trotter | # The owner dict contains the set of locks each thread owns. For
|
399 | aaae9bc0 | Guido Trotter | # performance each thread can access its own key without a global lock on
|
400 | aaae9bc0 | Guido Trotter | # this structure. It is paramount though that *no* other type of access is
|
401 | aaae9bc0 | Guido Trotter | # done to this structure (eg. no looping over its keys). *_owner helper
|
402 | aaae9bc0 | Guido Trotter | # function are defined to guarantee access is correct, but in general never
|
403 | aaae9bc0 | Guido Trotter | # do anything different than __owners[threading.currentThread()], or there
|
404 | aaae9bc0 | Guido Trotter | # will be trouble.
|
405 | aaae9bc0 | Guido Trotter | self.__owners = {}
|
406 | aaae9bc0 | Guido Trotter | |
407 | aaae9bc0 | Guido Trotter | def _is_owned(self): |
408 | aaae9bc0 | Guido Trotter | """Is the current thread a current level owner?"""
|
409 | aaae9bc0 | Guido Trotter | return threading.currentThread() in self.__owners |
410 | aaae9bc0 | Guido Trotter | |
411 | b2dabfd6 | Guido Trotter | def _add_owned(self, name=None): |
412 | aaae9bc0 | Guido Trotter | """Note the current thread owns the given lock"""
|
413 | b2dabfd6 | Guido Trotter | if name is None: |
414 | b2dabfd6 | Guido Trotter | if not self._is_owned(): |
415 | b2dabfd6 | Guido Trotter | self.__owners[threading.currentThread()] = set() |
416 | aaae9bc0 | Guido Trotter | else:
|
417 | b2dabfd6 | Guido Trotter | if self._is_owned(): |
418 | b2dabfd6 | Guido Trotter | self.__owners[threading.currentThread()].add(name)
|
419 | b2dabfd6 | Guido Trotter | else:
|
420 | b2dabfd6 | Guido Trotter | self.__owners[threading.currentThread()] = set([name]) |
421 | b2dabfd6 | Guido Trotter | |
422 | b2dabfd6 | Guido Trotter | def _del_owned(self, name=None): |
423 | aaae9bc0 | Guido Trotter | """Note the current thread owns the given lock"""
|
424 | aaae9bc0 | Guido Trotter | |
425 | b2dabfd6 | Guido Trotter | if name is not None: |
426 | b2dabfd6 | Guido Trotter | self.__owners[threading.currentThread()].remove(name)
|
427 | b2dabfd6 | Guido Trotter | |
428 | b2dabfd6 | Guido Trotter | # Only remove the key if we don't hold the set-lock as well
|
429 | b2dabfd6 | Guido Trotter | if (not self.__lock._is_owned() and |
430 | b2dabfd6 | Guido Trotter | not self.__owners[threading.currentThread()]): |
431 | aaae9bc0 | Guido Trotter | del self.__owners[threading.currentThread()] |
432 | aaae9bc0 | Guido Trotter | |
433 | aaae9bc0 | Guido Trotter | def _list_owned(self): |
434 | aaae9bc0 | Guido Trotter | """Get the set of resource names owned by the current thread"""
|
435 | aaae9bc0 | Guido Trotter | if self._is_owned(): |
436 | aaae9bc0 | Guido Trotter | return self.__owners[threading.currentThread()].copy() |
437 | aaae9bc0 | Guido Trotter | else:
|
438 | aaae9bc0 | Guido Trotter | return set() |
439 | aaae9bc0 | Guido Trotter | |
440 | aaae9bc0 | Guido Trotter | def __names(self): |
441 | aaae9bc0 | Guido Trotter | """Return the current set of names.
|
442 | aaae9bc0 | Guido Trotter |
|
443 | aaae9bc0 | Guido Trotter | Only call this function while holding __lock and don't iterate on the
|
444 | aaae9bc0 | Guido Trotter | result after releasing the lock.
|
445 | aaae9bc0 | Guido Trotter |
|
446 | aaae9bc0 | Guido Trotter | """
|
447 | 0cf257c5 | Guido Trotter | return self.__lockdict.keys() |
448 | aaae9bc0 | Guido Trotter | |
449 | aaae9bc0 | Guido Trotter | def _names(self): |
450 | aaae9bc0 | Guido Trotter | """Return a copy of the current set of elements.
|
451 | aaae9bc0 | Guido Trotter |
|
452 | aaae9bc0 | Guido Trotter | Used only for debugging purposes.
|
453 | cdb08f44 | Michael Hanselmann |
|
454 | aaae9bc0 | Guido Trotter | """
|
455 | d4803c24 | Guido Trotter | # If we don't already own the set-level lock acquired
|
456 | d4803c24 | Guido Trotter | # we'll get it and note we need to release it later.
|
457 | d4803c24 | Guido Trotter | release_lock = False
|
458 | d4803c24 | Guido Trotter | if not self.__lock._is_owned(): |
459 | d4803c24 | Guido Trotter | release_lock = True
|
460 | d4803c24 | Guido Trotter | self.__lock.acquire(shared=1) |
461 | aaae9bc0 | Guido Trotter | try:
|
462 | aaae9bc0 | Guido Trotter | result = self.__names()
|
463 | aaae9bc0 | Guido Trotter | finally:
|
464 | d4803c24 | Guido Trotter | if release_lock:
|
465 | d4803c24 | Guido Trotter | self.__lock.release()
|
466 | 0cf257c5 | Guido Trotter | return set(result) |
467 | aaae9bc0 | Guido Trotter | |
468 | aaae9bc0 | Guido Trotter | def acquire(self, names, blocking=1, shared=0): |
469 | aaae9bc0 | Guido Trotter | """Acquire a set of resource locks.
|
470 | aaae9bc0 | Guido Trotter |
|
471 | c41eea6e | Iustin Pop | @param names: the names of the locks which shall be acquired
|
472 | c41eea6e | Iustin Pop | (special lock names, or instance/node names)
|
473 | c41eea6e | Iustin Pop | @param shared: whether to acquire in shared mode; by default an
|
474 | c41eea6e | Iustin Pop | exclusive lock will be acquired
|
475 | c41eea6e | Iustin Pop | @param blocking: whether to block while trying to acquire or to
|
476 | c41eea6e | Iustin Pop | operate in try-lock mode (this locking mode is not supported yet)
|
477 | aaae9bc0 | Guido Trotter |
|
478 | c41eea6e | Iustin Pop | @return: True when all the locks are successfully acquired
|
479 | aaae9bc0 | Guido Trotter |
|
480 | c41eea6e | Iustin Pop | @raise errors.LockError: when any lock we try to acquire has
|
481 | c41eea6e | Iustin Pop | been deleted before we succeed. In this case none of the
|
482 | c41eea6e | Iustin Pop | locks requested will be acquired.
|
483 | aaae9bc0 | Guido Trotter |
|
484 | aaae9bc0 | Guido Trotter | """
|
485 | aaae9bc0 | Guido Trotter | if not blocking: |
486 | aaae9bc0 | Guido Trotter | # We don't have non-blocking mode for now
|
487 | aaae9bc0 | Guido Trotter | raise NotImplementedError |
488 | aaae9bc0 | Guido Trotter | |
489 | aaae9bc0 | Guido Trotter | # Check we don't already own locks at this level
|
490 | aaae9bc0 | Guido Trotter | assert not self._is_owned(), "Cannot acquire locks in the same set twice" |
491 | aaae9bc0 | Guido Trotter | |
492 | 3b7ed473 | Guido Trotter | if names is None: |
493 | 3b7ed473 | Guido Trotter | # If no names are given acquire the whole set by not letting new names
|
494 | 3b7ed473 | Guido Trotter | # being added before we release, and getting the current list of names.
|
495 | 3b7ed473 | Guido Trotter | # Some of them may then be deleted later, but we'll cope with this.
|
496 | 3b7ed473 | Guido Trotter | #
|
497 | 3b7ed473 | Guido Trotter | # We'd like to acquire this lock in a shared way, as it's nice if
|
498 | 3b7ed473 | Guido Trotter | # everybody else can use the instances at the same time. If are acquiring
|
499 | 3b7ed473 | Guido Trotter | # them exclusively though they won't be able to do this anyway, though,
|
500 | 3b7ed473 | Guido Trotter | # so we'll get the list lock exclusively as well in order to be able to
|
501 | 3b7ed473 | Guido Trotter | # do add() on the set while owning it.
|
502 | 3b7ed473 | Guido Trotter | self.__lock.acquire(shared=shared)
|
503 | b2dabfd6 | Guido Trotter | try:
|
504 | b2dabfd6 | Guido Trotter | # note we own the set-lock
|
505 | b2dabfd6 | Guido Trotter | self._add_owned()
|
506 | b2dabfd6 | Guido Trotter | names = self.__names()
|
507 | b2dabfd6 | Guido Trotter | except:
|
508 | b2dabfd6 | Guido Trotter | # We shouldn't have problems adding the lock to the owners list, but
|
509 | b2dabfd6 | Guido Trotter | # if we did we'll try to release this lock and re-raise exception.
|
510 | b2dabfd6 | Guido Trotter | # Of course something is going to be really wrong, after this.
|
511 | b2dabfd6 | Guido Trotter | self.__lock.release()
|
512 | b2dabfd6 | Guido Trotter | raise
|
513 | 3b7ed473 | Guido Trotter | |
514 | 806e20fd | Guido Trotter | try:
|
515 | 806e20fd | Guido Trotter | # Support passing in a single resource to acquire rather than many
|
516 | 806e20fd | Guido Trotter | if isinstance(names, basestring): |
517 | 806e20fd | Guido Trotter | names = [names] |
518 | 806e20fd | Guido Trotter | else:
|
519 | 2a21bc88 | Iustin Pop | names = sorted(names)
|
520 | 806e20fd | Guido Trotter | |
521 | 806e20fd | Guido Trotter | acquire_list = [] |
522 | 806e20fd | Guido Trotter | # First we look the locks up on __lockdict. We have no way of being sure
|
523 | 806e20fd | Guido Trotter | # they will still be there after, but this makes it a lot faster should
|
524 | 806e20fd | Guido Trotter | # just one of them be the already wrong
|
525 | 34ca3914 | Guido Trotter | for lname in utils.UniqueSequence(names): |
526 | 806e20fd | Guido Trotter | try:
|
527 | 4e07ec8c | Guido Trotter | lock = self.__lockdict[lname] # raises KeyError if lock is not there |
528 | 806e20fd | Guido Trotter | acquire_list.append((lname, lock)) |
529 | 806e20fd | Guido Trotter | except (KeyError): |
530 | 3b7ed473 | Guido Trotter | if self.__lock._is_owned(): |
531 | f12eadb3 | Iustin Pop | # We are acquiring all the set, it doesn't matter if this
|
532 | f12eadb3 | Iustin Pop | # particular element is not there anymore.
|
533 | 3b7ed473 | Guido Trotter | continue
|
534 | 3b7ed473 | Guido Trotter | else:
|
535 | 3b7ed473 | Guido Trotter | raise errors.LockError('non-existing lock in set (%s)' % lname) |
536 | 806e20fd | Guido Trotter | |
537 | 806e20fd | Guido Trotter | # This will hold the locknames we effectively acquired.
|
538 | 806e20fd | Guido Trotter | acquired = set()
|
539 | 806e20fd | Guido Trotter | # Now acquire_list contains a sorted list of resources and locks we want.
|
540 | 806e20fd | Guido Trotter | # In order to get them we loop on this (private) list and acquire() them.
|
541 | 806e20fd | Guido Trotter | # We gave no real guarantee they will still exist till this is done but
|
542 | 806e20fd | Guido Trotter | # .acquire() itself is safe and will alert us if the lock gets deleted.
|
543 | 806e20fd | Guido Trotter | for (lname, lock) in acquire_list: |
544 | aaae9bc0 | Guido Trotter | try:
|
545 | 806e20fd | Guido Trotter | lock.acquire(shared=shared) # raises LockError if the lock is deleted
|
546 | ea3f80bf | Guido Trotter | # now the lock cannot be deleted, we have it!
|
547 | b2dabfd6 | Guido Trotter | self._add_owned(name=lname)
|
548 | ea3f80bf | Guido Trotter | acquired.add(lname) |
549 | 806e20fd | Guido Trotter | except (errors.LockError):
|
550 | 3b7ed473 | Guido Trotter | if self.__lock._is_owned(): |
551 | f12eadb3 | Iustin Pop | # We are acquiring all the set, it doesn't matter if this
|
552 | f12eadb3 | Iustin Pop | # particular element is not there anymore.
|
553 | 3b7ed473 | Guido Trotter | continue
|
554 | 3b7ed473 | Guido Trotter | else:
|
555 | 3b7ed473 | Guido Trotter | name_fail = lname |
556 | 3b7ed473 | Guido Trotter | for lname in self._list_owned(): |
557 | 3b7ed473 | Guido Trotter | self.__lockdict[lname].release()
|
558 | b2dabfd6 | Guido Trotter | self._del_owned(name=lname)
|
559 | 3b7ed473 | Guido Trotter | raise errors.LockError('non-existing lock in set (%s)' % name_fail) |
560 | ea3f80bf | Guido Trotter | except:
|
561 | ea3f80bf | Guido Trotter | # We shouldn't have problems adding the lock to the owners list, but
|
562 | ea3f80bf | Guido Trotter | # if we did we'll try to release this lock and re-raise exception.
|
563 | ea3f80bf | Guido Trotter | # Of course something is going to be really wrong, after this.
|
564 | ea3f80bf | Guido Trotter | if lock._is_owned():
|
565 | ea3f80bf | Guido Trotter | lock.release() |
566 | 470ce2ee | Michael Hanselmann | raise
|
567 | 806e20fd | Guido Trotter | |
568 | 806e20fd | Guido Trotter | except:
|
569 | 3b7ed473 | Guido Trotter | # If something went wrong and we had the set-lock let's release it...
|
570 | 3b7ed473 | Guido Trotter | if self.__lock._is_owned(): |
571 | 3b7ed473 | Guido Trotter | self.__lock.release()
|
572 | 806e20fd | Guido Trotter | raise
|
573 | aaae9bc0 | Guido Trotter | |
574 | 0cc00929 | Guido Trotter | return acquired
|
575 | aaae9bc0 | Guido Trotter | |
576 | aaae9bc0 | Guido Trotter | def release(self, names=None): |
577 | aaae9bc0 | Guido Trotter | """Release a set of resource locks, at the same level.
|
578 | aaae9bc0 | Guido Trotter |
|
579 | aaae9bc0 | Guido Trotter | You must have acquired the locks, either in shared or in exclusive mode,
|
580 | aaae9bc0 | Guido Trotter | before releasing them.
|
581 | aaae9bc0 | Guido Trotter |
|
582 | c41eea6e | Iustin Pop | @param names: the names of the locks which shall be released
|
583 | c41eea6e | Iustin Pop | (defaults to all the locks acquired at that level).
|
584 | aaae9bc0 | Guido Trotter |
|
585 | aaae9bc0 | Guido Trotter | """
|
586 | aaae9bc0 | Guido Trotter | assert self._is_owned(), "release() on lock set while not owner" |
587 | aaae9bc0 | Guido Trotter | |
588 | aaae9bc0 | Guido Trotter | # Support passing in a single resource to release rather than many
|
589 | aaae9bc0 | Guido Trotter | if isinstance(names, basestring): |
590 | aaae9bc0 | Guido Trotter | names = [names] |
591 | aaae9bc0 | Guido Trotter | |
592 | aaae9bc0 | Guido Trotter | if names is None: |
593 | aaae9bc0 | Guido Trotter | names = self._list_owned()
|
594 | aaae9bc0 | Guido Trotter | else:
|
595 | aaae9bc0 | Guido Trotter | names = set(names)
|
596 | aaae9bc0 | Guido Trotter | assert self._list_owned().issuperset(names), ( |
597 | aaae9bc0 | Guido Trotter | "release() on unheld resources %s" %
|
598 | aaae9bc0 | Guido Trotter | names.difference(self._list_owned()))
|
599 | aaae9bc0 | Guido Trotter | |
600 | 3b7ed473 | Guido Trotter | # First of all let's release the "all elements" lock, if set.
|
601 | 3b7ed473 | Guido Trotter | # After this 'add' can work again
|
602 | 3b7ed473 | Guido Trotter | if self.__lock._is_owned(): |
603 | 3b7ed473 | Guido Trotter | self.__lock.release()
|
604 | b2dabfd6 | Guido Trotter | self._del_owned()
|
605 | 3b7ed473 | Guido Trotter | |
606 | aaae9bc0 | Guido Trotter | for lockname in names: |
607 | aaae9bc0 | Guido Trotter | # If we are sure the lock doesn't leave __lockdict without being
|
608 | aaae9bc0 | Guido Trotter | # exclusively held we can do this...
|
609 | aaae9bc0 | Guido Trotter | self.__lockdict[lockname].release()
|
610 | b2dabfd6 | Guido Trotter | self._del_owned(name=lockname)
|
611 | aaae9bc0 | Guido Trotter | |
612 | aaae9bc0 | Guido Trotter | def add(self, names, acquired=0, shared=0): |
613 | aaae9bc0 | Guido Trotter | """Add a new set of elements to the set
|
614 | aaae9bc0 | Guido Trotter |
|
615 | c41eea6e | Iustin Pop | @param names: names of the new elements to add
|
616 | c41eea6e | Iustin Pop | @param acquired: pre-acquire the new resource?
|
617 | c41eea6e | Iustin Pop | @param shared: is the pre-acquisition shared?
|
618 | aaae9bc0 | Guido Trotter |
|
619 | aaae9bc0 | Guido Trotter | """
|
620 | d2aff862 | Guido Trotter | # Check we don't already own locks at this level
|
621 | d2aff862 | Guido Trotter | assert not self._is_owned() or self.__lock._is_owned(shared=0), \ |
622 | d2aff862 | Guido Trotter | "Cannot add locks if the set is only partially owned, or shared"
|
623 | 3b7ed473 | Guido Trotter | |
624 | aaae9bc0 | Guido Trotter | # Support passing in a single resource to add rather than many
|
625 | aaae9bc0 | Guido Trotter | if isinstance(names, basestring): |
626 | aaae9bc0 | Guido Trotter | names = [names] |
627 | aaae9bc0 | Guido Trotter | |
628 | ab62526c | Guido Trotter | # If we don't already own the set-level lock acquired in an exclusive way
|
629 | 3b7ed473 | Guido Trotter | # we'll get it and note we need to release it later.
|
630 | 3b7ed473 | Guido Trotter | release_lock = False
|
631 | 3b7ed473 | Guido Trotter | if not self.__lock._is_owned(): |
632 | 3b7ed473 | Guido Trotter | release_lock = True
|
633 | 3b7ed473 | Guido Trotter | self.__lock.acquire()
|
634 | 3b7ed473 | Guido Trotter | |
635 | aaae9bc0 | Guido Trotter | try:
|
636 | 0cf257c5 | Guido Trotter | invalid_names = set(self.__names()).intersection(names) |
637 | aaae9bc0 | Guido Trotter | if invalid_names:
|
638 | aaae9bc0 | Guido Trotter | # This must be an explicit raise, not an assert, because assert is
|
639 | aaae9bc0 | Guido Trotter | # turned off when using optimization, and this can happen because of
|
640 | aaae9bc0 | Guido Trotter | # concurrency even if the user doesn't want it.
|
641 | aaae9bc0 | Guido Trotter | raise errors.LockError("duplicate add() (%s)" % invalid_names) |
642 | aaae9bc0 | Guido Trotter | |
643 | aaae9bc0 | Guido Trotter | for lockname in names: |
644 | aaae9bc0 | Guido Trotter | lock = SharedLock() |
645 | aaae9bc0 | Guido Trotter | |
646 | aaae9bc0 | Guido Trotter | if acquired:
|
647 | aaae9bc0 | Guido Trotter | lock.acquire(shared=shared) |
648 | aaae9bc0 | Guido Trotter | # now the lock cannot be deleted, we have it!
|
649 | aaae9bc0 | Guido Trotter | try:
|
650 | b2dabfd6 | Guido Trotter | self._add_owned(name=lockname)
|
651 | aaae9bc0 | Guido Trotter | except:
|
652 | aaae9bc0 | Guido Trotter | # We shouldn't have problems adding the lock to the owners list,
|
653 | aaae9bc0 | Guido Trotter | # but if we did we'll try to release this lock and re-raise
|
654 | aaae9bc0 | Guido Trotter | # exception. Of course something is going to be really wrong,
|
655 | aaae9bc0 | Guido Trotter | # after this. On the other hand the lock hasn't been added to the
|
656 | aaae9bc0 | Guido Trotter | # __lockdict yet so no other threads should be pending on it. This
|
657 | aaae9bc0 | Guido Trotter | # release is just a safety measure.
|
658 | aaae9bc0 | Guido Trotter | lock.release() |
659 | aaae9bc0 | Guido Trotter | raise
|
660 | aaae9bc0 | Guido Trotter | |
661 | aaae9bc0 | Guido Trotter | self.__lockdict[lockname] = lock
|
662 | aaae9bc0 | Guido Trotter | |
663 | aaae9bc0 | Guido Trotter | finally:
|
664 | 3b7ed473 | Guido Trotter | # Only release __lock if we were not holding it previously.
|
665 | 3b7ed473 | Guido Trotter | if release_lock:
|
666 | 3b7ed473 | Guido Trotter | self.__lock.release()
|
667 | aaae9bc0 | Guido Trotter | |
668 | aaae9bc0 | Guido Trotter | return True |
669 | aaae9bc0 | Guido Trotter | |
670 | aaae9bc0 | Guido Trotter | def remove(self, names, blocking=1): |
671 | aaae9bc0 | Guido Trotter | """Remove elements from the lock set.
|
672 | aaae9bc0 | Guido Trotter |
|
673 | aaae9bc0 | Guido Trotter | You can either not hold anything in the lockset or already hold a superset
|
674 | aaae9bc0 | Guido Trotter | of the elements you want to delete, exclusively.
|
675 | aaae9bc0 | Guido Trotter |
|
676 | c41eea6e | Iustin Pop | @param names: names of the resource to remove.
|
677 | c41eea6e | Iustin Pop | @param blocking: whether to block while trying to acquire or to
|
678 | c41eea6e | Iustin Pop | operate in try-lock mode (this locking mode is not supported
|
679 | c41eea6e | Iustin Pop | yet unless you are already holding exclusively the locks)
|
680 | aaae9bc0 | Guido Trotter |
|
681 | c41eea6e | Iustin Pop | @return:: a list of locks which we removed; the list is always
|
682 | c41eea6e | Iustin Pop | equal to the names list if we were holding all the locks
|
683 | c41eea6e | Iustin Pop | exclusively
|
684 | aaae9bc0 | Guido Trotter |
|
685 | aaae9bc0 | Guido Trotter | """
|
686 | aaae9bc0 | Guido Trotter | if not blocking and not self._is_owned(): |
687 | aaae9bc0 | Guido Trotter | # We don't have non-blocking mode for now
|
688 | aaae9bc0 | Guido Trotter | raise NotImplementedError |
689 | aaae9bc0 | Guido Trotter | |
690 | aaae9bc0 | Guido Trotter | # Support passing in a single resource to remove rather than many
|
691 | aaae9bc0 | Guido Trotter | if isinstance(names, basestring): |
692 | aaae9bc0 | Guido Trotter | names = [names] |
693 | aaae9bc0 | Guido Trotter | |
694 | aaae9bc0 | Guido Trotter | # If we own any subset of this lock it must be a superset of what we want
|
695 | aaae9bc0 | Guido Trotter | # to delete. The ownership must also be exclusive, but that will be checked
|
696 | aaae9bc0 | Guido Trotter | # by the lock itself.
|
697 | aaae9bc0 | Guido Trotter | assert not self._is_owned() or self._list_owned().issuperset(names), ( |
698 | aaae9bc0 | Guido Trotter | "remove() on acquired lockset while not owning all elements")
|
699 | aaae9bc0 | Guido Trotter | |
700 | 3f404fc5 | Guido Trotter | removed = [] |
701 | aaae9bc0 | Guido Trotter | |
702 | aaae9bc0 | Guido Trotter | for lname in names: |
703 | aaae9bc0 | Guido Trotter | # Calling delete() acquires the lock exclusively if we don't already own
|
704 | aaae9bc0 | Guido Trotter | # it, and causes all pending and subsequent lock acquires to fail. It's
|
705 | aaae9bc0 | Guido Trotter | # fine to call it out of order because delete() also implies release(),
|
706 | aaae9bc0 | Guido Trotter | # and the assertion above guarantees that if we either already hold
|
707 | aaae9bc0 | Guido Trotter | # everything we want to delete, or we hold none.
|
708 | aaae9bc0 | Guido Trotter | try:
|
709 | aaae9bc0 | Guido Trotter | self.__lockdict[lname].delete()
|
710 | 3f404fc5 | Guido Trotter | removed.append(lname) |
711 | aaae9bc0 | Guido Trotter | except (KeyError, errors.LockError): |
712 | aaae9bc0 | Guido Trotter | # This cannot happen if we were already holding it, verify:
|
713 | aaae9bc0 | Guido Trotter | assert not self._is_owned(), "remove failed while holding lockset" |
714 | aaae9bc0 | Guido Trotter | else:
|
715 | aaae9bc0 | Guido Trotter | # If no LockError was raised we are the ones who deleted the lock.
|
716 | aaae9bc0 | Guido Trotter | # This means we can safely remove it from lockdict, as any further or
|
717 | aaae9bc0 | Guido Trotter | # pending delete() or acquire() will fail (and nobody can have the lock
|
718 | aaae9bc0 | Guido Trotter | # since before our call to delete()).
|
719 | aaae9bc0 | Guido Trotter | #
|
720 | aaae9bc0 | Guido Trotter | # This is done in an else clause because if the exception was thrown
|
721 | aaae9bc0 | Guido Trotter | # it's the job of the one who actually deleted it.
|
722 | aaae9bc0 | Guido Trotter | del self.__lockdict[lname] |
723 | aaae9bc0 | Guido Trotter | # And let's remove it from our private list if we owned it.
|
724 | aaae9bc0 | Guido Trotter | if self._is_owned(): |
725 | b2dabfd6 | Guido Trotter | self._del_owned(name=lname)
|
726 | aaae9bc0 | Guido Trotter | |
727 | 3f404fc5 | Guido Trotter | return removed
|
728 | aaae9bc0 | Guido Trotter | |
729 | 7ee7c0c7 | Guido Trotter | |
730 | 7ee7c0c7 | Guido Trotter | # Locking levels, must be acquired in increasing order.
|
731 | 7ee7c0c7 | Guido Trotter | # Current rules are:
|
732 | 7ee7c0c7 | Guido Trotter | # - at level LEVEL_CLUSTER resides the Big Ganeti Lock (BGL) which must be
|
733 | 7ee7c0c7 | Guido Trotter | # acquired before performing any operation, either in shared or in exclusive
|
734 | 7ee7c0c7 | Guido Trotter | # mode. acquiring the BGL in exclusive mode is discouraged and should be
|
735 | 7ee7c0c7 | Guido Trotter | # avoided.
|
736 | 7ee7c0c7 | Guido Trotter | # - at levels LEVEL_NODE and LEVEL_INSTANCE reside node and instance locks.
|
737 | 7ee7c0c7 | Guido Trotter | # If you need more than one node, or more than one instance, acquire them at
|
738 | 7ee7c0c7 | Guido Trotter | # the same time.
|
739 | 7ee7c0c7 | Guido Trotter | LEVEL_CLUSTER = 0
|
740 | 04e1bfaf | Guido Trotter | LEVEL_INSTANCE = 1
|
741 | 04e1bfaf | Guido Trotter | LEVEL_NODE = 2
|
742 | 7ee7c0c7 | Guido Trotter | |
743 | 7ee7c0c7 | Guido Trotter | LEVELS = [LEVEL_CLUSTER, |
744 | 04e1bfaf | Guido Trotter | LEVEL_INSTANCE, |
745 | 04e1bfaf | Guido Trotter | LEVEL_NODE] |
746 | 7ee7c0c7 | Guido Trotter | |
747 | 7ee7c0c7 | Guido Trotter | # Lock levels which are modifiable
|
748 | 7ee7c0c7 | Guido Trotter | LEVELS_MOD = [LEVEL_NODE, LEVEL_INSTANCE] |
749 | 7ee7c0c7 | Guido Trotter | |
750 | ea205dbc | Michael Hanselmann | LEVEL_NAMES = { |
751 | ea205dbc | Michael Hanselmann | LEVEL_CLUSTER: "cluster",
|
752 | ea205dbc | Michael Hanselmann | LEVEL_INSTANCE: "instance",
|
753 | ea205dbc | Michael Hanselmann | LEVEL_NODE: "node",
|
754 | ea205dbc | Michael Hanselmann | } |
755 | ea205dbc | Michael Hanselmann | |
756 | 08a6c581 | Guido Trotter | # Constant for the big ganeti lock
|
757 | 7ee7c0c7 | Guido Trotter | BGL = 'BGL'
|
758 | 7ee7c0c7 | Guido Trotter | |
759 | 7ee7c0c7 | Guido Trotter | |
760 | 7ee7c0c7 | Guido Trotter | class GanetiLockManager: |
761 | 7ee7c0c7 | Guido Trotter | """The Ganeti Locking Library
|
762 | 7ee7c0c7 | Guido Trotter |
|
763 | 5bbd3f7f | Michael Hanselmann | The purpose of this small library is to manage locking for ganeti clusters
|
764 | 7ee7c0c7 | Guido Trotter | in a central place, while at the same time doing dynamic checks against
|
765 | 7ee7c0c7 | Guido Trotter | possible deadlocks. It will also make it easier to transition to a different
|
766 | 7ee7c0c7 | Guido Trotter | lock type should we migrate away from python threads.
|
767 | 7ee7c0c7 | Guido Trotter |
|
768 | 7ee7c0c7 | Guido Trotter | """
|
769 | 7ee7c0c7 | Guido Trotter | _instance = None
|
770 | 7ee7c0c7 | Guido Trotter | |
771 | 7ee7c0c7 | Guido Trotter | def __init__(self, nodes=None, instances=None): |
772 | 7ee7c0c7 | Guido Trotter | """Constructs a new GanetiLockManager object.
|
773 | 7ee7c0c7 | Guido Trotter |
|
774 | 4e07ec8c | Guido Trotter | There should be only a GanetiLockManager object at any time, so this
|
775 | 4e07ec8c | Guido Trotter | function raises an error if this is not the case.
|
776 | 7ee7c0c7 | Guido Trotter |
|
777 | c41eea6e | Iustin Pop | @param nodes: list of node names
|
778 | c41eea6e | Iustin Pop | @param instances: list of instance names
|
779 | 7ee7c0c7 | Guido Trotter |
|
780 | 7ee7c0c7 | Guido Trotter | """
|
781 | c41eea6e | Iustin Pop | assert self.__class__._instance is None, \ |
782 | c41eea6e | Iustin Pop | "double GanetiLockManager instance"
|
783 | c41eea6e | Iustin Pop | |
784 | 7ee7c0c7 | Guido Trotter | self.__class__._instance = self |
785 | 7ee7c0c7 | Guido Trotter | |
786 | 7ee7c0c7 | Guido Trotter | # The keyring contains all the locks, at their level and in the correct
|
787 | 7ee7c0c7 | Guido Trotter | # locking order.
|
788 | 7ee7c0c7 | Guido Trotter | self.__keyring = {
|
789 | 7ee7c0c7 | Guido Trotter | LEVEL_CLUSTER: LockSet([BGL]), |
790 | 7ee7c0c7 | Guido Trotter | LEVEL_NODE: LockSet(nodes), |
791 | 7ee7c0c7 | Guido Trotter | LEVEL_INSTANCE: LockSet(instances), |
792 | 7ee7c0c7 | Guido Trotter | } |
793 | 7ee7c0c7 | Guido Trotter | |
794 | 7ee7c0c7 | Guido Trotter | def _names(self, level): |
795 | 7ee7c0c7 | Guido Trotter | """List the lock names at the given level.
|
796 | 7ee7c0c7 | Guido Trotter |
|
797 | c41eea6e | Iustin Pop | This can be used for debugging/testing purposes.
|
798 | c41eea6e | Iustin Pop |
|
799 | c41eea6e | Iustin Pop | @param level: the level whose list of locks to get
|
800 | 7ee7c0c7 | Guido Trotter |
|
801 | 7ee7c0c7 | Guido Trotter | """
|
802 | 7ee7c0c7 | Guido Trotter | assert level in LEVELS, "Invalid locking level %s" % level |
803 | 7ee7c0c7 | Guido Trotter | return self.__keyring[level]._names() |
804 | 7ee7c0c7 | Guido Trotter | |
805 | 7ee7c0c7 | Guido Trotter | def _is_owned(self, level): |
806 | 7ee7c0c7 | Guido Trotter | """Check whether we are owning locks at the given level
|
807 | 7ee7c0c7 | Guido Trotter |
|
808 | 7ee7c0c7 | Guido Trotter | """
|
809 | 7ee7c0c7 | Guido Trotter | return self.__keyring[level]._is_owned() |
810 | 7ee7c0c7 | Guido Trotter | |
811 | d4f4b3e7 | Guido Trotter | is_owned = _is_owned |
812 | d4f4b3e7 | Guido Trotter | |
813 | 7ee7c0c7 | Guido Trotter | def _list_owned(self, level): |
814 | 7ee7c0c7 | Guido Trotter | """Get the set of owned locks at the given level
|
815 | 7ee7c0c7 | Guido Trotter |
|
816 | 7ee7c0c7 | Guido Trotter | """
|
817 | 7ee7c0c7 | Guido Trotter | return self.__keyring[level]._list_owned() |
818 | 7ee7c0c7 | Guido Trotter | |
819 | 7ee7c0c7 | Guido Trotter | def _upper_owned(self, level): |
820 | 7ee7c0c7 | Guido Trotter | """Check that we don't own any lock at a level greater than the given one.
|
821 | 7ee7c0c7 | Guido Trotter |
|
822 | 7ee7c0c7 | Guido Trotter | """
|
823 | 7ee7c0c7 | Guido Trotter | # This way of checking only works if LEVELS[i] = i, which we check for in
|
824 | 7ee7c0c7 | Guido Trotter | # the test cases.
|
825 | 7ee7c0c7 | Guido Trotter | return utils.any((self._is_owned(l) for l in LEVELS[level + 1:])) |
826 | 7ee7c0c7 | Guido Trotter | |
827 | 7ee7c0c7 | Guido Trotter | def _BGL_owned(self): |
828 | 7ee7c0c7 | Guido Trotter | """Check if the current thread owns the BGL.
|
829 | 7ee7c0c7 | Guido Trotter |
|
830 | 7ee7c0c7 | Guido Trotter | Both an exclusive or a shared acquisition work.
|
831 | 7ee7c0c7 | Guido Trotter |
|
832 | 7ee7c0c7 | Guido Trotter | """
|
833 | 7ee7c0c7 | Guido Trotter | return BGL in self.__keyring[LEVEL_CLUSTER]._list_owned() |
834 | 7ee7c0c7 | Guido Trotter | |
835 | 7ee7c0c7 | Guido Trotter | def _contains_BGL(self, level, names): |
836 | c41eea6e | Iustin Pop | """Check if the level contains the BGL.
|
837 | c41eea6e | Iustin Pop |
|
838 | c41eea6e | Iustin Pop | Check if acting on the given level and set of names will change
|
839 | c41eea6e | Iustin Pop | the status of the Big Ganeti Lock.
|
840 | 7ee7c0c7 | Guido Trotter |
|
841 | 7ee7c0c7 | Guido Trotter | """
|
842 | 7ee7c0c7 | Guido Trotter | return level == LEVEL_CLUSTER and (names is None or BGL in names) |
843 | 7ee7c0c7 | Guido Trotter | |
844 | 7ee7c0c7 | Guido Trotter | def acquire(self, level, names, blocking=1, shared=0): |
845 | 7ee7c0c7 | Guido Trotter | """Acquire a set of resource locks, at the same level.
|
846 | 7ee7c0c7 | Guido Trotter |
|
847 | c41eea6e | Iustin Pop | @param level: the level at which the locks shall be acquired;
|
848 | 5bbd3f7f | Michael Hanselmann | it must be a member of LEVELS.
|
849 | c41eea6e | Iustin Pop | @param names: the names of the locks which shall be acquired
|
850 | c41eea6e | Iustin Pop | (special lock names, or instance/node names)
|
851 | c41eea6e | Iustin Pop | @param shared: whether to acquire in shared mode; by default
|
852 | c41eea6e | Iustin Pop | an exclusive lock will be acquired
|
853 | c41eea6e | Iustin Pop | @param blocking: whether to block while trying to acquire or to
|
854 | c41eea6e | Iustin Pop | operate in try-lock mode (this locking mode is not supported yet)
|
855 | 7ee7c0c7 | Guido Trotter |
|
856 | 7ee7c0c7 | Guido Trotter | """
|
857 | 7ee7c0c7 | Guido Trotter | assert level in LEVELS, "Invalid locking level %s" % level |
858 | 7ee7c0c7 | Guido Trotter | |
859 | 7ee7c0c7 | Guido Trotter | # Check that we are either acquiring the Big Ganeti Lock or we already own
|
860 | 7ee7c0c7 | Guido Trotter | # it. Some "legacy" opcodes need to be sure they are run non-concurrently
|
861 | 7ee7c0c7 | Guido Trotter | # so even if we've migrated we need to at least share the BGL to be
|
862 | 7ee7c0c7 | Guido Trotter | # compatible with them. Of course if we own the BGL exclusively there's no
|
863 | 7ee7c0c7 | Guido Trotter | # point in acquiring any other lock, unless perhaps we are half way through
|
864 | 7ee7c0c7 | Guido Trotter | # the migration of the current opcode.
|
865 | 7ee7c0c7 | Guido Trotter | assert (self._contains_BGL(level, names) or self._BGL_owned()), ( |
866 | 7ee7c0c7 | Guido Trotter | "You must own the Big Ganeti Lock before acquiring any other")
|
867 | 7ee7c0c7 | Guido Trotter | |
868 | 7ee7c0c7 | Guido Trotter | # Check we don't own locks at the same or upper levels.
|
869 | 21a6c826 | Guido Trotter | assert not self._upper_owned(level), ("Cannot acquire locks at a level" |
870 | 7ee7c0c7 | Guido Trotter | " while owning some at a greater one")
|
871 | 7ee7c0c7 | Guido Trotter | |
872 | 7ee7c0c7 | Guido Trotter | # Acquire the locks in the set.
|
873 | 7ee7c0c7 | Guido Trotter | return self.__keyring[level].acquire(names, shared=shared, |
874 | 7ee7c0c7 | Guido Trotter | blocking=blocking) |
875 | 7ee7c0c7 | Guido Trotter | |
876 | 7ee7c0c7 | Guido Trotter | def release(self, level, names=None): |
877 | 7ee7c0c7 | Guido Trotter | """Release a set of resource locks, at the same level.
|
878 | 7ee7c0c7 | Guido Trotter |
|
879 | c41eea6e | Iustin Pop | You must have acquired the locks, either in shared or in exclusive
|
880 | c41eea6e | Iustin Pop | mode, before releasing them.
|
881 | 7ee7c0c7 | Guido Trotter |
|
882 | c41eea6e | Iustin Pop | @param level: the level at which the locks shall be released;
|
883 | 5bbd3f7f | Michael Hanselmann | it must be a member of LEVELS
|
884 | c41eea6e | Iustin Pop | @param names: the names of the locks which shall be released
|
885 | c41eea6e | Iustin Pop | (defaults to all the locks acquired at that level)
|
886 | 7ee7c0c7 | Guido Trotter |
|
887 | 7ee7c0c7 | Guido Trotter | """
|
888 | 7ee7c0c7 | Guido Trotter | assert level in LEVELS, "Invalid locking level %s" % level |
889 | 7ee7c0c7 | Guido Trotter | assert (not self._contains_BGL(level, names) or |
890 | 7ee7c0c7 | Guido Trotter | not self._upper_owned(LEVEL_CLUSTER)), ( |
891 | 7ee7c0c7 | Guido Trotter | "Cannot release the Big Ganeti Lock while holding something"
|
892 | 7ee7c0c7 | Guido Trotter | " at upper levels")
|
893 | 7ee7c0c7 | Guido Trotter | |
894 | 7ee7c0c7 | Guido Trotter | # Release will complain if we don't own the locks already
|
895 | 7ee7c0c7 | Guido Trotter | return self.__keyring[level].release(names) |
896 | 7ee7c0c7 | Guido Trotter | |
897 | 7ee7c0c7 | Guido Trotter | def add(self, level, names, acquired=0, shared=0): |
898 | 7ee7c0c7 | Guido Trotter | """Add locks at the specified level.
|
899 | 7ee7c0c7 | Guido Trotter |
|
900 | c41eea6e | Iustin Pop | @param level: the level at which the locks shall be added;
|
901 | 5bbd3f7f | Michael Hanselmann | it must be a member of LEVELS_MOD.
|
902 | c41eea6e | Iustin Pop | @param names: names of the locks to acquire
|
903 | c41eea6e | Iustin Pop | @param acquired: whether to acquire the newly added locks
|
904 | c41eea6e | Iustin Pop | @param shared: whether the acquisition will be shared
|
905 | c41eea6e | Iustin Pop |
|
906 | 7ee7c0c7 | Guido Trotter | """
|
907 | 7ee7c0c7 | Guido Trotter | assert level in LEVELS_MOD, "Invalid or immutable level %s" % level |
908 | 7ee7c0c7 | Guido Trotter | assert self._BGL_owned(), ("You must own the BGL before performing other" |
909 | 7ee7c0c7 | Guido Trotter | " operations")
|
910 | 7ee7c0c7 | Guido Trotter | assert not self._upper_owned(level), ("Cannot add locks at a level" |
911 | 7ee7c0c7 | Guido Trotter | " while owning some at a greater one")
|
912 | 7ee7c0c7 | Guido Trotter | return self.__keyring[level].add(names, acquired=acquired, shared=shared) |
913 | 7ee7c0c7 | Guido Trotter | |
914 | 7ee7c0c7 | Guido Trotter | def remove(self, level, names, blocking=1): |
915 | 7ee7c0c7 | Guido Trotter | """Remove locks from the specified level.
|
916 | 7ee7c0c7 | Guido Trotter |
|
917 | c41eea6e | Iustin Pop | You must either already own the locks you are trying to remove
|
918 | c41eea6e | Iustin Pop | exclusively or not own any lock at an upper level.
|
919 | 7ee7c0c7 | Guido Trotter |
|
920 | c41eea6e | Iustin Pop | @param level: the level at which the locks shall be removed;
|
921 | c41eea6e | Iustin Pop | it must be a member of LEVELS_MOD
|
922 | c41eea6e | Iustin Pop | @param names: the names of the locks which shall be removed
|
923 | c41eea6e | Iustin Pop | (special lock names, or instance/node names)
|
924 | c41eea6e | Iustin Pop | @param blocking: whether to block while trying to operate in
|
925 | c41eea6e | Iustin Pop | try-lock mode (this locking mode is not supported yet)
|
926 | 7ee7c0c7 | Guido Trotter |
|
927 | 7ee7c0c7 | Guido Trotter | """
|
928 | 7ee7c0c7 | Guido Trotter | assert level in LEVELS_MOD, "Invalid or immutable level %s" % level |
929 | 7ee7c0c7 | Guido Trotter | assert self._BGL_owned(), ("You must own the BGL before performing other" |
930 | 7ee7c0c7 | Guido Trotter | " operations")
|
931 | f12eadb3 | Iustin Pop | # Check we either own the level or don't own anything from here
|
932 | f12eadb3 | Iustin Pop | # up. LockSet.remove() will check the case in which we don't own
|
933 | f12eadb3 | Iustin Pop | # all the needed resources, or we have a shared ownership.
|
934 | 7ee7c0c7 | Guido Trotter | assert self._is_owned(level) or not self._upper_owned(level), ( |
935 | 7ee7c0c7 | Guido Trotter | "Cannot remove locks at a level while not owning it or"
|
936 | 7ee7c0c7 | Guido Trotter | " owning some at a greater one")
|
937 | cdb08f44 | Michael Hanselmann | return self.__keyring[level].remove(names, blocking=blocking) |