88
88
>>> t = MemoryTransport()
89
89
>>> l = LockDir(t, 'sample-lock')
91
>>> token = l.wait_lock()
92
92
>>> # do something here
98
# TODO: We sometimes have the problem that our attempt to rename '1234' to
99
# 'held' fails because the transport server moves into an existing directory,
100
# rather than failing the rename. If we made the info file name the same as
101
# the locked directory name we would avoid this problem because moving into
102
# the held directory would implicitly clash. However this would not mesh with
103
# the existing locking code and needs a new format of the containing object.
104
# -- robertc, mbp 20070628
99
from cStringIO import StringIO
109
101
from bzrlib import (
115
104
import bzrlib.config
116
from bzrlib.decorators import only_raises
117
105
from bzrlib.errors import (
118
106
DirectoryNotEmpty,
120
108
LockBreakMismatch,
131
117
from bzrlib.trace import mutter, note
132
from bzrlib.osutils import format_delta, rand_chars, get_host_name
118
from bzrlib.transport import Transport
119
from bzrlib.osutils import rand_chars, format_delta
120
from bzrlib.rio import read_stanza, Stanza
135
from bzrlib.lazy_import import lazy_import
136
lazy_import(globals(), """
137
from bzrlib import rio
140
124
# XXX: At the moment there is no consideration of thread safety on LockDir
141
125
# objects. This should perhaps be updated - e.g. if two threads try to take a
194
179
def create(self, mode=None):
195
180
"""Create the on-disk lock.
197
This is typically only called when the object/directory containing the
182
This is typically only called when the object/directory containing the
198
183
directory is first created. The lock is not held when it's created.
200
self._trace("create lock directory")
202
self.transport.mkdir(self.path, mode=mode)
203
except (TransportError, PathError), e:
204
raise LockFailed(self, e)
207
def _attempt_lock(self):
208
"""Make the pending directory and attempt to rename into place.
210
If the rename succeeds, we read back the info file to check that we
213
If we fail to acquire the lock, this method is responsible for
214
cleaning up the pending directory if possible. (But it doesn't do
217
:returns: The nonce of the lock, if it was successfully acquired.
219
:raises LockContention: If the lock is held by someone else. The exception
220
contains the info of the current holder of the lock.
185
if self.transport.is_readonly():
186
raise UnlockableTransport(self.transport)
187
self.transport.mkdir(self.path, mode=mode)
189
def attempt_lock(self):
190
"""Take the lock; fail if it's already held.
192
If you wish to block until the lock can be obtained, call wait_lock()
222
self._trace("lock_write...")
223
start_time = time.time()
225
tmpname = self._create_pending_dir()
226
except (errors.TransportError, PathError), e:
227
self._trace("... failed to create pending dir, %s", e)
228
raise LockFailed(self, e)
195
if self._fake_read_lock:
196
raise LockContention(self)
197
if self.transport.is_readonly():
198
raise UnlockableTransport(self.transport)
200
tmpname = '%s/pending.%s.tmp' % (self.path, rand_chars(20))
202
self.transport.mkdir(tmpname)
204
# This may raise a FileExists exception
205
# which is okay, it will be caught later and determined
206
# to be a LockContention.
207
self.create(mode=self._dir_modebits)
209
# After creating the lock directory, try again
210
self.transport.mkdir(tmpname)
212
self.nonce = rand_chars(20)
213
info_bytes = self._prepare_info()
214
# We use put_file_non_atomic because we just created a new unique
215
# directory so we don't have to worry about files existing there.
216
# We'll rename the whole directory into place to get atomic
218
self.transport.put_bytes_non_atomic(tmpname + self.__INFO_NAME,
230
221
self.transport.rename(tmpname, self._held_dir)
231
except (errors.TransportError, PathError, DirectoryNotEmpty,
232
FileExists, ResourceBusy), e:
233
self._trace("... contention, %s", e)
234
self._remove_pending_dir(tmpname)
235
raise LockContention(self)
237
self._trace("... lock failed, %s", e)
238
self._remove_pending_dir(tmpname)
222
self._lock_held = True
224
except errors.PermissionDenied:
240
# We must check we really got the lock, because Launchpad's sftp
241
# server at one time had a bug were the rename would successfully
242
# move the new directory into the existing directory, which was
243
# incorrect. It's possible some other servers or filesystems will
244
# have a similar bug allowing someone to think they got the lock
245
# when it's already held.
247
# See <https://bugs.launchpad.net/bzr/+bug/498378> for one case.
249
# Strictly the check is unnecessary and a waste of time for most
250
# people, but probably worth trapping if something is wrong.
252
self._trace("after locking, info=%r", info)
254
raise LockFailed(self, "lock was renamed into place, but "
256
if info.get('nonce') != self.nonce:
257
self._trace("rename succeeded, "
258
"but lock is still held by someone else")
226
except (PathError, DirectoryNotEmpty, FileExists, ResourceBusy), e:
227
mutter("contention on %r: %s", self, e)
259
228
raise LockContention(self)
260
self._lock_held = True
261
self._trace("... lock succeeded after %dms",
262
(time.time() - start_time) * 1000)
265
def _remove_pending_dir(self, tmpname):
266
"""Remove the pending directory
268
This is called if we failed to rename into place, so that the pending
269
dirs don't clutter up the lockdir.
271
self._trace("remove %s", tmpname)
273
self.transport.delete(tmpname + self.__INFO_NAME)
274
self.transport.rmdir(tmpname)
276
note("error removing pending lock: %s", e)
278
def _create_pending_dir(self):
279
tmpname = '%s/%s.tmp' % (self.path, rand_chars(10))
281
self.transport.mkdir(tmpname)
283
# This may raise a FileExists exception
284
# which is okay, it will be caught later and determined
285
# to be a LockContention.
286
self._trace("lock directory does not exist, creating it")
287
self.create(mode=self._dir_modebits)
288
# After creating the lock directory, try again
289
self.transport.mkdir(tmpname)
290
self.nonce = rand_chars(20)
291
info_bytes = self._prepare_info()
292
# We use put_file_non_atomic because we just created a new unique
293
# directory so we don't have to worry about files existing there.
294
# We'll rename the whole directory into place to get atomic
296
self.transport.put_bytes_non_atomic(tmpname + self.__INFO_NAME,
300
@only_raises(LockNotHeld, LockBroken)
301
230
def unlock(self):
302
231
"""Release a held lock
305
234
self._fake_read_lock = False
307
236
if not self._lock_held:
308
return lock.cant_unlock_not_held(self)
237
raise LockNotHeld(self)
309
238
if self._locked_via_token:
310
239
self._locked_via_token = False
311
240
self._lock_held = False
313
old_nonce = self.nonce
314
242
# rename before deleting, because we can't atomically remove the
316
start_time = time.time()
317
self._trace("unlocking")
318
244
tmpname = '%s/releasing.%s.tmp' % (self.path, rand_chars(20))
319
245
# gotta own it to unlock
321
247
self.transport.rename(self._held_dir, tmpname)
322
248
self._lock_held = False
323
249
self.transport.delete(tmpname + self.__INFO_NAME)
325
self.transport.rmdir(tmpname)
326
except DirectoryNotEmpty, e:
327
# There might have been junk left over by a rename that moved
328
# another locker within the 'held' directory. do a slower
329
# deletion where we list the directory and remove everything
332
# Maybe this should be broader to allow for ftp servers with
333
# non-specific error messages?
334
self._trace("doing recursive deletion of non-empty directory "
336
self.transport.delete_tree(tmpname)
337
self._trace("... unlock succeeded after %dms",
338
(time.time() - start_time) * 1000)
339
result = lock.LockResult(self.transport.abspath(self.path),
341
for hook in self.hooks['lock_released']:
250
self.transport.rmdir(tmpname)
344
252
def break_lock(self):
345
253
"""Break a lock not held by this instance of LockDir.
347
255
This is a UI centric function: it uses the bzrlib.ui.ui_factory to
348
256
prompt for input if a lock is detected and there is any doubt about
349
257
it possibly being still active.
351
:returns: LockResult for the broken lock.
353
259
self._check_not_locked()
355
holder_info = self.peek()
356
except LockCorrupt, e:
357
# The lock info is corrupt.
358
if bzrlib.ui.ui_factory.get_boolean("Break (corrupt %r)" % (self,)):
359
self.force_break_corrupt(e.file_data)
260
holder_info = self.peek()
361
261
if holder_info is not None:
362
262
lock_info = '\n'.join(self._format_lock_info(holder_info))
363
if bzrlib.ui.ui_factory.confirm_action(
364
"Break %(lock_info)s", 'bzrlib.lockdir.break',
365
dict(lock_info=lock_info)):
366
result = self.force_break(holder_info)
367
bzrlib.ui.ui_factory.show_message(
368
"Broke lock %s" % result.lock_url)
263
if bzrlib.ui.ui_factory.get_boolean("Break %s" % lock_info):
264
self.force_break(holder_info)
370
266
def force_break(self, dead_holder_info):
371
267
"""Release a lock held by another process.
405
299
raise LockBreakMismatch(self, broken_info, dead_holder_info)
406
300
self.transport.delete(broken_info_path)
407
301
self.transport.rmdir(tmpname)
408
result = lock.LockResult(self.transport.abspath(self.path),
409
current_info.get('nonce'))
410
for hook in self.hooks['lock_broken']:
414
def force_break_corrupt(self, corrupt_info_lines):
415
"""Release a lock that has been corrupted.
417
This is very similar to force_break, it except it doesn't assume that
418
self.peek() can work.
420
:param corrupt_info_lines: the lines of the corrupted info file, used
421
to check that the lock hasn't changed between reading the (corrupt)
422
info file and calling force_break_corrupt.
424
# XXX: this copes with unparseable info files, but what about missing
425
# info files? Or missing lock dirs?
426
self._check_not_locked()
427
tmpname = '%s/broken.%s.tmp' % (self.path, rand_chars(20))
428
self.transport.rename(self._held_dir, tmpname)
429
# check that we actually broke the right lock, not someone else;
430
# there's a small race window between checking it and doing the
432
broken_info_path = tmpname + self.__INFO_NAME
433
broken_content = self.transport.get_bytes(broken_info_path)
434
broken_lines = osutils.split_lines(broken_content)
435
if broken_lines != corrupt_info_lines:
436
raise LockBreakMismatch(self, broken_lines, corrupt_info_lines)
437
self.transport.delete(broken_info_path)
438
self.transport.rmdir(tmpname)
439
result = lock.LockResult(self.transport.abspath(self.path))
440
for hook in self.hooks['lock_broken']:
443
303
def _check_not_locked(self):
444
304
"""If the lock is held by this instance, raise an error."""
464
324
if info.get('nonce') != self.nonce:
465
325
# there is a lock, but not ours
466
326
raise LockBroken(self)
468
328
def _read_info_file(self, path):
469
329
"""Read one given info file.
471
331
peek() reads the info file of the lock holder, if any.
473
return self._parse_info(self.transport.get_bytes(path))
333
return self._parse_info(self.transport.get(path))
476
336
"""Check if the lock is held by anyone.
478
If it is held, this returns the lock info structure as a dict
338
If it is held, this returns the lock info structure as a rio Stanza,
479
339
which contains some information about the current lock holder.
480
340
Otherwise returns None.
483
343
info = self._read_info_file(self._held_info_path)
484
self._trace("peek -> held")
344
assert isinstance(info, dict), \
345
"bad parse result %r" % info
486
347
except NoSuchFile, e:
487
self._trace("peek -> not held")
489
350
def _prepare_info(self):
490
351
"""Write information about a pending lock to a temporary file.
492
354
# XXX: is creating this here inefficient?
493
355
config = bzrlib.config.GlobalConfig()
357
user = config.user_email()
358
except errors.NoEmailInUsername:
495
359
user = config.username()
496
except errors.NoWhoami:
497
user = osutils.getuser_unicode()
498
s = rio.Stanza(hostname=get_host_name(),
360
s = Stanza(hostname=socket.gethostname(),
499
361
pid=str(os.getpid()),
500
362
start_time=str(int(time.time())),
501
363
nonce=self.nonce,
504
366
return s.to_string()
506
def _parse_info(self, info_bytes):
507
lines = osutils.split_lines(info_bytes)
509
stanza = rio.read_stanza(lines)
510
except ValueError, e:
511
mutter('Corrupt lock info file: %r', lines)
512
raise LockCorrupt("could not parse lock info file: " + str(e),
515
# see bug 185013; we fairly often end up with the info file being
516
# empty after an interruption; we could log a message here but
517
# there may not be much we can say
520
return stanza.as_dict()
522
def attempt_lock(self):
523
"""Take the lock; fail if it's already held.
525
If you wish to block until the lock can be obtained, call wait_lock()
528
:return: The lock token.
529
:raises LockContention: if the lock is held by someone else.
531
if self._fake_read_lock:
532
raise LockContention(self)
533
result = self._attempt_lock()
534
hook_result = lock.LockResult(self.transport.abspath(self.path),
536
for hook in self.hooks['lock_acquired']:
540
def lock_url_for_display(self):
541
"""Give a nicely-printable representation of the URL of this lock."""
542
# As local lock urls are correct we display them.
543
# We avoid displaying remote lock urls.
544
lock_url = self.transport.abspath(self.path)
545
if lock_url.startswith('file://'):
546
lock_url = lock_url.split('.bzr/')[0]
551
def wait_lock(self, timeout=None, poll=None, max_attempts=None):
368
def _parse_info(self, info_file):
369
return read_stanza(info_file.readlines()).as_dict()
371
def wait_lock(self, timeout=None, poll=None):
552
372
"""Wait a certain period for a lock.
554
374
If the lock can be acquired within the bounded time, it
556
376
is raised. Either way, this function should return within
557
377
approximately `timeout` seconds. (It may be a bit more if
558
378
a transport operation takes a long time to complete.)
560
:param timeout: Approximate maximum amount of time to wait for the
563
:param poll: Delay in seconds between retrying the lock.
565
:param max_attempts: Maximum number of times to try to lock.
567
:return: The lock token.
569
380
if timeout is None:
570
381
timeout = _DEFAULT_TIMEOUT_SECONDS
572
383
poll = _DEFAULT_POLL_SECONDS
573
# XXX: the transport interface doesn't let us guard against operations
574
# there taking a long time, so the total elapsed time or poll interval
575
# may be more than was requested.
385
# XXX: the transport interface doesn't let us guard
386
# against operations there taking a long time.
576
387
deadline = time.time() + timeout
577
388
deadline_str = None
580
lock_url = self.lock_url_for_display()
584
return self.attempt_lock()
585
394
except LockContention:
586
# possibly report the blockage, then try again
588
# TODO: In a few cases, we find out that there's contention by
589
# reading the held info and observing that it's not ours. In
590
# those cases it's a bit redundant to read it again. However,
591
# the normal case (??) is that the rename fails and so we
592
# don't know who holds the lock. For simplicity we peek
594
396
new_info = self.peek()
397
mutter('last_info: %s, new info: %s', last_info, new_info)
595
398
if new_info is not None and new_info != last_info:
596
399
if last_info is None:
597
400
start = 'Unable to obtain'
602
405
if deadline_str is None:
603
406
deadline_str = time.strftime('%H:%M:%S',
604
407
time.localtime(deadline))
605
user, hostname, pid, time_ago = formatted_info
606
msg = ('%s lock %s ' # lock_url
610
'[process #%s], ' # pid
611
'acquired %s.') # time ago
612
msg_args = [start, lock_url, user, hostname, pid, time_ago]
614
msg += ('\nWill continue to try until %s, unless '
616
msg_args.append(deadline_str)
617
msg += '\nSee "bzr help break-lock" for more.'
618
self._report_function(msg, *msg_args)
619
if (max_attempts is not None) and (attempt_count >= max_attempts):
620
self._trace("exceeded %d attempts")
621
raise LockContention(self)
408
self._report_function('%s %s\n'
410
'%s\n' # locked ... ago
411
'Will continue to try until %s\n',
622
418
if time.time() + poll < deadline:
623
self._trace("waiting %ss", poll)
626
# As timeout is always 0 for remote locks
627
# this block is applicable only for local
629
self._trace("timeout after waiting %ss", timeout)
630
raise LockContention('(local)', lock_url)
421
raise LockContention(self)
632
423
def leave_in_place(self):
633
424
self._locked_via_token = True
659
450
self._locked_via_token = True
662
return self.wait_lock()
454
return self.peek().get('nonce')
664
456
def lock_read(self):
665
457
"""Compatibility-mode shared lock.
667
LockDir doesn't support shared read-only locks, so this
459
LockDir doesn't support shared read-only locks, so this
668
460
just pretends that the lock is taken but really does nothing.
670
# At the moment Branches are commonly locked for read, but
462
# At the moment Branches are commonly locked for read, but
671
463
# we can't rely on that remotely. Once this is cleaned up,
672
# reenable this warning to prevent it coming back in
464
# reenable this warning to prevent it coming back in
673
465
# -- mbp 20060303
674
466
## warn("LockDir.lock_read falls back to write lock")
675
467
if self._lock_held or self._fake_read_lock:
676
468
raise LockContention(self)
677
469
self._fake_read_lock = True
471
def wait(self, timeout=20, poll=0.5):
472
"""Wait a certain period for a lock to be released."""
473
# XXX: the transport interface doesn't let us guard
474
# against operations there taking a long time.
475
deadline = time.time() + timeout
479
if time.time() + poll < deadline:
482
raise LockContention(self)
679
484
def _format_lock_info(self, info):
680
485
"""Turn the contents of peek() into something for the user"""
681
start_time = info.get('start_time')
682
if start_time is None:
683
time_ago = '(unknown)'
685
time_ago = format_delta(time.time() - int(info['start_time']))
686
user = info.get('user', '<unknown>')
687
hostname = info.get('hostname', '<unknown>')
688
pid = info.get('pid', '<unknown>')
486
lock_url = self.transport.abspath(self.path)
487
delta = time.time() - int(info['start_time'])
489
'lock %s' % (lock_url,),
490
'held by %(user)s on host %(hostname)s [process #%(pid)s]' % info,
491
'locked %s' % (format_delta(delta),),
696
494
def validate_token(self, token):
added
removed
bzrlib/lockdir.py
