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 StringIO import StringIO
115
101
import bzrlib.config
116
from bzrlib.decorators import only_raises
117
102
from bzrlib.errors import (
118
103
DirectoryNotEmpty,
120
105
LockBreakMismatch,
130
from bzrlib.trace import mutter, note
131
from bzrlib.osutils import format_delta, rand_chars, get_host_name
134
from bzrlib.lazy_import import lazy_import
135
lazy_import(globals(), """
136
from bzrlib import rio
114
from bzrlib.trace import mutter
115
from bzrlib.transport import Transport
116
from bzrlib.osutils import rand_chars
117
from bzrlib.rio import RioWriter, read_stanza, Stanza
139
119
# XXX: At the moment there is no consideration of thread safety on LockDir
140
120
# objects. This should perhaps be updated - e.g. if two threads try to take a
193
170
def create(self, mode=None):
194
171
"""Create the on-disk lock.
196
This is typically only called when the object/directory containing the
173
This is typically only called when the object/directory containing the
197
174
directory is first created. The lock is not held when it's created.
199
self._trace("create lock directory")
201
self.transport.mkdir(self.path, mode=mode)
202
except (TransportError, PathError), e:
203
raise LockFailed(self, e)
206
def _attempt_lock(self):
207
"""Make the pending directory and attempt to rename into place.
209
If the rename succeeds, we read back the info file to check that we
212
If we fail to acquire the lock, this method is responsible for
213
cleaning up the pending directory if possible. (But it doesn't do
216
:returns: The nonce of the lock, if it was successfully acquired.
218
:raises LockContention: If the lock is held by someone else. The exception
219
contains the info of the current holder of the lock.
176
if self.transport.is_readonly():
177
raise UnlockableTransport(self.transport)
178
self.transport.mkdir(self.path, mode=mode)
180
def attempt_lock(self):
181
"""Take the lock; fail if it's already held.
183
If you wish to block until the lock can be obtained, call wait_lock()
221
self._trace("lock_write...")
222
start_time = time.time()
224
tmpname = self._create_pending_dir()
225
except (errors.TransportError, PathError), e:
226
self._trace("... failed to create pending dir, %s", e)
227
raise LockFailed(self, e)
186
if self._fake_read_lock:
187
raise LockContention(self)
188
if self.transport.is_readonly():
189
raise UnlockableTransport(self.transport)
191
tmpname = '%s/pending.%s.tmp' % (self.path, rand_chars(20))
192
self.transport.mkdir(tmpname)
194
self._prepare_info(sio)
196
# append will create a new file; we use append rather than put
197
# because we don't want to write to a temporary file and rename
198
# into place, because that's going to happen to the whole
200
self.transport.append(tmpname + self.__INFO_NAME, sio)
229
201
self.transport.rename(tmpname, self._held_dir)
230
except (errors.TransportError, PathError, DirectoryNotEmpty,
231
FileExists, ResourceBusy), e:
232
self._trace("... contention, %s", e)
233
self._remove_pending_dir(tmpname)
234
raise LockContention(self)
236
self._trace("... lock failed, %s", e)
237
self._remove_pending_dir(tmpname)
239
# We must check we really got the lock, because Launchpad's sftp
240
# server at one time had a bug were the rename would successfully
241
# move the new directory into the existing directory, which was
242
# incorrect. It's possible some other servers or filesystems will
243
# have a similar bug allowing someone to think they got the lock
244
# when it's already held.
246
# See <https://bugs.launchpad.net/bzr/+bug/498378> for one case.
248
# Strictly the check is unnecessary and a waste of time for most
249
# people, but probably worth trapping if something is wrong.
251
self._trace("after locking, info=%r", info)
253
raise LockFailed(self, "lock was renamed into place, but "
255
if info.get('nonce') != self.nonce:
256
self._trace("rename succeeded, "
257
"but lock is still held by someone else")
258
raise LockContention(self)
259
self._lock_held = True
260
self._trace("... lock succeeded after %dms",
261
(time.time() - start_time) * 1000)
264
def _remove_pending_dir(self, tmpname):
265
"""Remove the pending directory
267
This is called if we failed to rename into place, so that the pending
268
dirs don't clutter up the lockdir.
270
self._trace("remove %s", tmpname)
272
self.transport.delete(tmpname + self.__INFO_NAME)
273
self.transport.rmdir(tmpname)
275
note("error removing pending lock: %s", e)
277
def _create_pending_dir(self):
278
tmpname = '%s/%s.tmp' % (self.path, rand_chars(10))
280
self.transport.mkdir(tmpname)
282
# This may raise a FileExists exception
283
# which is okay, it will be caught later and determined
284
# to be a LockContention.
285
self._trace("lock directory does not exist, creating it")
286
self.create(mode=self._dir_modebits)
287
# After creating the lock directory, try again
288
self.transport.mkdir(tmpname)
289
self.nonce = rand_chars(20)
290
info_bytes = self._prepare_info()
291
# We use put_file_non_atomic because we just created a new unique
292
# directory so we don't have to worry about files existing there.
293
# We'll rename the whole directory into place to get atomic
295
self.transport.put_bytes_non_atomic(tmpname + self.__INFO_NAME,
299
@only_raises(LockNotHeld, LockBroken)
202
self._lock_held = True
204
except (PathError, DirectoryNotEmpty, FileExists, ResourceBusy), e:
205
mutter("contention on %r: %s", self, e)
206
raise LockContention(self)
300
208
def unlock(self):
301
209
"""Release a held lock
304
212
self._fake_read_lock = False
306
214
if not self._lock_held:
307
return lock.cant_unlock_not_held(self)
308
if self._locked_via_token:
309
self._locked_via_token = False
310
self._lock_held = False
312
old_nonce = self.nonce
313
# rename before deleting, because we can't atomically remove the
315
start_time = time.time()
316
self._trace("unlocking")
317
tmpname = '%s/releasing.%s.tmp' % (self.path, rand_chars(20))
318
# gotta own it to unlock
320
self.transport.rename(self._held_dir, tmpname)
321
self._lock_held = False
322
self.transport.delete(tmpname + self.__INFO_NAME)
324
self.transport.rmdir(tmpname)
325
except DirectoryNotEmpty, e:
326
# There might have been junk left over by a rename that moved
327
# another locker within the 'held' directory. do a slower
328
# deletion where we list the directory and remove everything
331
# Maybe this should be broader to allow for ftp servers with
332
# non-specific error messages?
333
self._trace("doing recursive deletion of non-empty directory "
335
self.transport.delete_tree(tmpname)
336
self._trace("... unlock succeeded after %dms",
337
(time.time() - start_time) * 1000)
338
result = lock.LockResult(self.transport.abspath(self.path),
340
for hook in self.hooks['lock_released']:
215
raise LockNotHeld(self)
216
# rename before deleting, because we can't atomically remove the whole
218
tmpname = '%s/releasing.%s.tmp' % (self.path, rand_chars(20))
219
# gotta own it to unlock
221
self.transport.rename(self._held_dir, tmpname)
222
self._lock_held = False
223
self.transport.delete(tmpname + self.__INFO_NAME)
224
self.transport.rmdir(tmpname)
343
226
def break_lock(self):
344
227
"""Break a lock not held by this instance of LockDir.
419
302
if info.get('nonce') != self.nonce:
420
303
# there is a lock, but not ours
421
304
raise LockBroken(self)
423
306
def _read_info_file(self, path):
424
307
"""Read one given info file.
426
309
peek() reads the info file of the lock holder, if any.
428
return self._parse_info(self.transport.get_bytes(path))
311
return self._parse_info(self.transport.get(path))
431
314
"""Check if the lock is held by anyone.
433
If it is held, this returns the lock info structure as a dict
316
If it is held, this returns the lock info structure as a rio Stanza,
434
317
which contains some information about the current lock holder.
435
318
Otherwise returns None.
438
321
info = self._read_info_file(self._held_info_path)
439
self._trace("peek -> held")
322
assert isinstance(info, dict), \
323
"bad parse result %r" % info
441
325
except NoSuchFile, e:
442
self._trace("peek -> not held")
444
def _prepare_info(self):
328
def _prepare_info(self, outf):
445
329
"""Write information about a pending lock to a temporary file.
447
332
# XXX: is creating this here inefficient?
448
333
config = bzrlib.config.GlobalConfig()
450
user = config.username()
451
except errors.NoWhoami:
452
user = osutils.getuser_unicode()
453
s = rio.Stanza(hostname=get_host_name(),
334
s = Stanza(hostname=socket.gethostname(),
454
335
pid=str(os.getpid()),
455
336
start_time=str(int(time.time())),
456
337
nonce=self.nonce,
338
user=config.user_email(),
461
def _parse_info(self, info_bytes):
462
stanza = rio.read_stanza(osutils.split_lines(info_bytes))
464
# see bug 185013; we fairly often end up with the info file being
465
# empty after an interruption; we could log a message here but
466
# there may not be much we can say
469
return stanza.as_dict()
471
def attempt_lock(self):
472
"""Take the lock; fail if it's already held.
474
If you wish to block until the lock can be obtained, call wait_lock()
477
:return: The lock token.
478
:raises LockContention: if the lock is held by someone else.
480
if self._fake_read_lock:
481
raise LockContention(self)
482
result = self._attempt_lock()
483
hook_result = lock.LockResult(self.transport.abspath(self.path),
485
for hook in self.hooks['lock_acquired']:
489
def wait_lock(self, timeout=None, poll=None, max_attempts=None):
340
RioWriter(outf).write_stanza(s)
342
def _parse_info(self, info_file):
343
return read_stanza(info_file.readlines()).as_dict()
345
def wait_lock(self, timeout=_DEFAULT_TIMEOUT_SECONDS,
346
poll=_DEFAULT_POLL_SECONDS):
490
347
"""Wait a certain period for a lock.
492
349
If the lock can be acquired within the bounded time, it
494
351
is raised. Either way, this function should return within
495
352
approximately `timeout` seconds. (It may be a bit more if
496
353
a transport operation takes a long time to complete.)
498
:param timeout: Approximate maximum amount of time to wait for the
501
:param poll: Delay in seconds between retrying the lock.
503
:param max_attempts: Maximum number of times to try to lock.
505
:return: The lock token.
508
timeout = _DEFAULT_TIMEOUT_SECONDS
510
poll = _DEFAULT_POLL_SECONDS
511
# XXX: the transport interface doesn't let us guard against operations
512
# there taking a long time, so the total elapsed time or poll interval
513
# may be more than was requested.
355
# XXX: the transport interface doesn't let us guard
356
# against operations there taking a long time.
514
357
deadline = time.time() + timeout
521
return self.attempt_lock()
522
362
except LockContention:
523
# possibly report the blockage, then try again
525
# TODO: In a few cases, we find out that there's contention by
526
# reading the held info and observing that it's not ours. In
527
# those cases it's a bit redundant to read it again. However,
528
# the normal case (??) is that the rename fails and so we
529
# don't know who holds the lock. For simplicity we peek
531
new_info = self.peek()
532
if new_info is not None and new_info != last_info:
533
if last_info is None:
534
start = 'Unable to obtain'
536
start = 'Lock owner changed for'
538
formatted_info = self._format_lock_info(new_info)
539
if deadline_str is None:
540
deadline_str = time.strftime('%H:%M:%S',
541
time.localtime(deadline))
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]
549
user, hostname, pid, time_ago = formatted_info
550
msg = ('%s lock %s ' # lock_url
554
'[process #%s], ' # pid
555
'acquired %s.') # time ago
556
msg_args = [start, lock_url, user, hostname, pid, time_ago]
558
msg += ('\nWill continue to try until %s, unless '
560
msg_args.append(deadline_str)
561
msg += '\nSee "bzr help break-lock" for more.'
562
self._report_function(msg, *msg_args)
563
if (max_attempts is not None) and (attempt_count >= max_attempts):
564
self._trace("exceeded %d attempts")
565
raise LockContention(self)
566
364
if time.time() + poll < deadline:
567
self._trace("waiting %ss", poll)
570
# As timeout is always 0 for remote locks
571
# this block is applicable only for local
573
self._trace("timeout after waiting %ss", timeout)
574
raise LockContention('(local)', lock_url)
576
def leave_in_place(self):
577
self._locked_via_token = True
579
def dont_leave_in_place(self):
580
self._locked_via_token = False
582
def lock_write(self, token=None):
583
"""Wait for and acquire the lock.
585
:param token: if this is already locked, then lock_write will fail
586
unless the token matches the existing lock.
587
:returns: a token if this instance supports tokens, otherwise None.
588
:raises TokenLockingNotSupported: when a token is given but this
589
instance doesn't support using token locks.
590
:raises MismatchedToken: if the specified token doesn't match the token
591
of the existing lock.
593
A token should be passed in if you know that you have locked the object
594
some other way, and need to synchronise this object's state with that
597
XXX: docstring duplicated from LockableFiles.lock_write.
599
if token is not None:
600
self.validate_token(token)
602
self._lock_held = True
603
self._locked_via_token = True
606
return self.wait_lock()
367
raise LockContention(self)
369
def lock_write(self):
370
"""Wait for and acquire the lock."""
608
373
def lock_read(self):
609
374
"""Compatibility-mode shared lock.
611
LockDir doesn't support shared read-only locks, so this
376
LockDir doesn't support shared read-only locks, so this
612
377
just pretends that the lock is taken but really does nothing.
614
# At the moment Branches are commonly locked for read, but
379
# At the moment Branches are commonly locked for read, but
615
380
# we can't rely on that remotely. Once this is cleaned up,
616
# reenable this warning to prevent it coming back in
381
# reenable this warning to prevent it coming back in
617
382
# -- mbp 20060303
618
383
## warn("LockDir.lock_read falls back to write lock")
619
384
if self._lock_held or self._fake_read_lock:
620
385
raise LockContention(self)
621
386
self._fake_read_lock = True
623
def _format_lock_info(self, info):
624
"""Turn the contents of peek() into something for the user"""
625
start_time = info.get('start_time')
626
if start_time is None:
627
time_ago = '(unknown)'
629
time_ago = format_delta(time.time() - int(info['start_time']))
630
user = info.get('user', '<unknown>')
631
hostname = info.get('hostname', '<unknown>')
632
pid = info.get('pid', '<unknown>')
640
def validate_token(self, token):
641
if token is not None:
647
lock_token = info.get('nonce')
648
if token != lock_token:
649
raise errors.TokenMismatch(token, lock_token)
651
self._trace("revalidated by token %r", token)
653
def _trace(self, format, *args):
654
if 'lock' not in debug.debug_flags:
656
mutter(str(self) + ": " + (format % args))
388
def wait(self, timeout=20, poll=0.5):
389
"""Wait a certain period for a lock to be released."""
390
# XXX: the transport interface doesn't let us guard
391
# against operations there taking a long time.
392
deadline = time.time() + timeout
396
if time.time() + poll < deadline:
399
raise LockContention(self)
added
removed
bzrlib/lockdir.py
