88
88
>>> t = MemoryTransport()
89
89
>>> l = LockDir(t, 'sample-lock')
91
>>> token = l.wait_lock()
92
92
>>> # do something here
95
Some classes of stale locks can be predicted by checking: the host name is the
96
same as the local host name; the user name is the same as the local user; the
97
process id no longer exists. The check on user name is not strictly necessary
98
but helps protect against colliding host names.
102
# TODO: We sometimes have the problem that our attempt to rename '1234' to
103
# 'held' fails because the transport server moves into an existing directory,
104
# rather than failing the rename. If we made the info file name the same as
105
# the locked directory name we would avoid this problem because moving into
106
# the held directory would implicitly clash. However this would not mesh with
107
# the existing locking code and needs a new format of the containing object.
108
# -- robertc, mbp 20070628
99
from cStringIO import StringIO
114
101
from bzrlib import (
123
from bzrlib.decorators import only_raises
124
105
from bzrlib.errors import (
125
106
DirectoryNotEmpty,
127
108
LockBreakMismatch,
138
117
from bzrlib.trace import mutter, note
139
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
141
from bzrlib.lazy_import import lazy_import
142
lazy_import(globals(), """
143
from bzrlib import rio
146
124
# XXX: At the moment there is no consideration of thread safety on LockDir
147
125
# objects. This should perhaps be updated - e.g. if two threads try to take a
206
179
def create(self, mode=None):
207
180
"""Create the on-disk lock.
209
This is typically only called when the object/directory containing the
182
This is typically only called when the object/directory containing the
210
183
directory is first created. The lock is not held when it's created.
212
self._trace("create lock directory")
214
self.transport.mkdir(self.path, mode=mode)
215
except (TransportError, PathError), e:
216
raise LockFailed(self, e)
218
def _attempt_lock(self):
219
"""Make the pending directory and attempt to rename into place.
221
If the rename succeeds, we read back the info file to check that we
224
If we fail to acquire the lock, this method is responsible for
225
cleaning up the pending directory if possible. (But it doesn't do
228
:returns: The nonce of the lock, if it was successfully acquired.
230
:raises LockContention: If the lock is held by someone else. The
231
exception 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()
233
self._trace("lock_write...")
234
start_time = time.time()
195
if self._fake_read_lock:
196
raise LockContention(self)
197
if self.transport.is_readonly():
198
raise UnlockableTransport(self.transport)
236
tmpname = self._create_pending_dir()
237
except (errors.TransportError, PathError), e:
238
self._trace("... failed to create pending dir, %s", e)
239
raise LockFailed(self, e)
200
tmpname = '%s/pending.%s.tmp' % (self.path, rand_chars(20))
242
self.transport.rename(tmpname, self._held_dir)
244
except (errors.TransportError, PathError, DirectoryNotEmpty,
245
FileExists, ResourceBusy), e:
246
self._trace("... contention, %s", e)
247
other_holder = self.peek()
248
self._trace("other holder is %r" % other_holder)
250
self._handle_lock_contention(other_holder)
252
self._remove_pending_dir(tmpname)
255
self._trace("... lock failed, %s", e)
256
self._remove_pending_dir(tmpname)
258
# We must check we really got the lock, because Launchpad's sftp
259
# server at one time had a bug were the rename would successfully
260
# move the new directory into the existing directory, which was
261
# incorrect. It's possible some other servers or filesystems will
262
# have a similar bug allowing someone to think they got the lock
263
# when it's already held.
265
# See <https://bugs.launchpad.net/bzr/+bug/498378> for one case.
267
# Strictly the check is unnecessary and a waste of time for most
268
# people, but probably worth trapping if something is wrong.
270
self._trace("after locking, info=%r", info)
272
raise LockFailed(self, "lock was renamed into place, but "
274
if info.get('nonce') != self.nonce:
275
self._trace("rename succeeded, "
276
"but lock is still held by someone else")
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,
221
self.transport.rename(tmpname, self._held_dir)
222
self._lock_held = True
224
except errors.PermissionDenied:
226
except (PathError, DirectoryNotEmpty, FileExists, ResourceBusy), e:
227
mutter("contention on %r: %s", self, e)
277
228
raise LockContention(self)
278
self._lock_held = True
279
self._trace("... lock succeeded after %dms",
280
(time.time() - start_time) * 1000)
283
def _handle_lock_contention(self, other_holder):
284
"""A lock we want to take is held by someone else.
286
This function can: tell the user about it; possibly detect that it's
287
safe or appropriate to steal the lock, or just raise an exception.
289
If this function returns (without raising an exception) the lock will
292
:param other_holder: A LockHeldInfo for the current holder; note that
293
it might be None if the lock can be seen to be held but the info
296
if (other_holder is not None):
297
if other_holder.is_lock_holder_known_dead():
298
if self.get_config().get('locks.steal_dead'):
299
ui.ui_factory.show_user_warning(
301
lock_url=urlutils.join(self.transport.base, self.path),
302
other_holder_info=unicode(other_holder))
303
self.force_break(other_holder)
304
self._trace("stole lock from dead holder")
306
raise LockContention(self)
308
def _remove_pending_dir(self, tmpname):
309
"""Remove the pending directory
311
This is called if we failed to rename into place, so that the pending
312
dirs don't clutter up the lockdir.
314
self._trace("remove %s", tmpname)
316
self.transport.delete(tmpname + self.__INFO_NAME)
317
self.transport.rmdir(tmpname)
319
note("error removing pending lock: %s", e)
321
def _create_pending_dir(self):
322
tmpname = '%s/%s.tmp' % (self.path, rand_chars(10))
324
self.transport.mkdir(tmpname)
326
# This may raise a FileExists exception
327
# which is okay, it will be caught later and determined
328
# to be a LockContention.
329
self._trace("lock directory does not exist, creating it")
330
self.create(mode=self._dir_modebits)
331
# After creating the lock directory, try again
332
self.transport.mkdir(tmpname)
333
info = LockHeldInfo.for_this_process(self.extra_holder_info)
334
self.nonce = info.get('nonce')
335
# We use put_file_non_atomic because we just created a new unique
336
# directory so we don't have to worry about files existing there.
337
# We'll rename the whole directory into place to get atomic
339
self.transport.put_bytes_non_atomic(tmpname + self.__INFO_NAME,
343
@only_raises(LockNotHeld, LockBroken)
344
230
def unlock(self):
345
231
"""Release a held lock
348
234
self._fake_read_lock = False
350
236
if not self._lock_held:
351
return lock.cant_unlock_not_held(self)
237
raise LockNotHeld(self)
352
238
if self._locked_via_token:
353
239
self._locked_via_token = False
354
240
self._lock_held = False
356
old_nonce = self.nonce
357
242
# rename before deleting, because we can't atomically remove the
359
start_time = time.time()
360
self._trace("unlocking")
361
244
tmpname = '%s/releasing.%s.tmp' % (self.path, rand_chars(20))
362
245
# gotta own it to unlock
364
247
self.transport.rename(self._held_dir, tmpname)
365
248
self._lock_held = False
366
249
self.transport.delete(tmpname + self.__INFO_NAME)
368
self.transport.rmdir(tmpname)
369
except DirectoryNotEmpty, e:
370
# There might have been junk left over by a rename that moved
371
# another locker within the 'held' directory. do a slower
372
# deletion where we list the directory and remove everything
375
# Maybe this should be broader to allow for ftp servers with
376
# non-specific error messages?
377
self._trace("doing recursive deletion of non-empty directory "
379
self.transport.delete_tree(tmpname)
380
self._trace("... unlock succeeded after %dms",
381
(time.time() - start_time) * 1000)
382
result = lock.LockResult(self.transport.abspath(self.path),
384
for hook in self.hooks['lock_released']:
250
self.transport.rmdir(tmpname)
387
252
def break_lock(self):
388
253
"""Break a lock not held by this instance of LockDir.
390
This is a UI centric function: it uses the ui.ui_factory to
255
This is a UI centric function: it uses the bzrlib.ui.ui_factory to
391
256
prompt for input if a lock is detected and there is any doubt about
392
it possibly being still active. force_break is the non-interactive
395
:returns: LockResult for the broken lock.
257
it possibly being still active.
397
259
self._check_not_locked()
399
holder_info = self.peek()
400
except LockCorrupt, e:
401
# The lock info is corrupt.
402
if ui.ui_factory.get_boolean(u"Break (corrupt %r)" % (self,)):
403
self.force_break_corrupt(e.file_data)
260
holder_info = self.peek()
405
261
if holder_info is not None:
406
if ui.ui_factory.confirm_action(
407
u"Break %(lock_info)s",
408
'bzrlib.lockdir.break',
409
dict(lock_info=unicode(holder_info))):
410
result = self.force_break(holder_info)
411
ui.ui_factory.show_message(
412
"Broke lock %s" % result.lock_url)
262
lock_info = '\n'.join(self._format_lock_info(holder_info))
263
if bzrlib.ui.ui_factory.get_boolean("Break %s" % lock_info):
264
self.force_break(holder_info)
414
266
def force_break(self, dead_holder_info):
415
267
"""Release a lock held by another process.
450
299
raise LockBreakMismatch(self, broken_info, dead_holder_info)
451
300
self.transport.delete(broken_info_path)
452
301
self.transport.rmdir(tmpname)
453
result = lock.LockResult(self.transport.abspath(self.path),
454
current_info.get('nonce'))
455
for hook in self.hooks['lock_broken']:
459
def force_break_corrupt(self, corrupt_info_lines):
460
"""Release a lock that has been corrupted.
462
This is very similar to force_break, it except it doesn't assume that
463
self.peek() can work.
465
:param corrupt_info_lines: the lines of the corrupted info file, used
466
to check that the lock hasn't changed between reading the (corrupt)
467
info file and calling force_break_corrupt.
469
# XXX: this copes with unparseable info files, but what about missing
470
# info files? Or missing lock dirs?
471
self._check_not_locked()
472
tmpname = '%s/broken.%s.tmp' % (self.path, rand_chars(20))
473
self.transport.rename(self._held_dir, tmpname)
474
# check that we actually broke the right lock, not someone else;
475
# there's a small race window between checking it and doing the
477
broken_info_path = tmpname + self.__INFO_NAME
478
broken_content = self.transport.get_bytes(broken_info_path)
479
broken_lines = osutils.split_lines(broken_content)
480
if broken_lines != corrupt_info_lines:
481
raise LockBreakMismatch(self, broken_lines, corrupt_info_lines)
482
self.transport.delete(broken_info_path)
483
self.transport.rmdir(tmpname)
484
result = lock.LockResult(self.transport.abspath(self.path))
485
for hook in self.hooks['lock_broken']:
488
303
def _check_not_locked(self):
489
304
"""If the lock is held by this instance, raise an error."""
509
324
if info.get('nonce') != self.nonce:
510
325
# there is a lock, but not ours
511
326
raise LockBroken(self)
513
328
def _read_info_file(self, path):
514
329
"""Read one given info file.
516
331
peek() reads the info file of the lock holder, if any.
518
return LockHeldInfo.from_info_file_bytes(
519
self.transport.get_bytes(path))
333
return self._parse_info(self.transport.get(path))
522
336
"""Check if the lock is held by anyone.
524
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,
525
339
which contains some information about the current lock holder.
526
340
Otherwise returns None.
529
343
info = self._read_info_file(self._held_info_path)
530
self._trace("peek -> held")
344
assert isinstance(info, dict), \
345
"bad parse result %r" % info
532
347
except NoSuchFile, e:
533
self._trace("peek -> not held")
535
350
def _prepare_info(self):
536
351
"""Write information about a pending lock to a temporary file.
539
def attempt_lock(self):
540
"""Take the lock; fail if it's already held.
542
If you wish to block until the lock can be obtained, call wait_lock()
545
:return: The lock token.
546
:raises LockContention: if the lock is held by someone else.
548
if self._fake_read_lock:
549
raise LockContention(self)
550
result = self._attempt_lock()
551
hook_result = lock.LockResult(self.transport.abspath(self.path),
553
for hook in self.hooks['lock_acquired']:
557
def lock_url_for_display(self):
558
"""Give a nicely-printable representation of the URL of this lock."""
559
# As local lock urls are correct we display them.
560
# We avoid displaying remote lock urls.
561
lock_url = self.transport.abspath(self.path)
562
if lock_url.startswith('file://'):
563
lock_url = lock_url.split('.bzr/')[0]
568
def wait_lock(self, timeout=None, poll=None, max_attempts=None):
354
# XXX: is creating this here inefficient?
355
config = bzrlib.config.GlobalConfig()
357
user = config.user_email()
358
except errors.NoEmailInUsername:
359
user = config.username()
360
s = Stanza(hostname=socket.gethostname(),
361
pid=str(os.getpid()),
362
start_time=str(int(time.time())),
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):
569
372
"""Wait a certain period for a lock.
571
374
If the lock can be acquired within the bounded time, it
573
376
is raised. Either way, this function should return within
574
377
approximately `timeout` seconds. (It may be a bit more if
575
378
a transport operation takes a long time to complete.)
577
:param timeout: Approximate maximum amount of time to wait for the
580
:param poll: Delay in seconds between retrying the lock.
582
:param max_attempts: Maximum number of times to try to lock.
584
:return: The lock token.
586
380
if timeout is None:
587
381
timeout = _DEFAULT_TIMEOUT_SECONDS
589
383
poll = _DEFAULT_POLL_SECONDS
590
# XXX: the transport interface doesn't let us guard against operations
591
# there taking a long time, so the total elapsed time or poll interval
592
# may be more than was requested.
385
# XXX: the transport interface doesn't let us guard
386
# against operations there taking a long time.
593
387
deadline = time.time() + timeout
594
388
deadline_str = None
597
lock_url = self.lock_url_for_display()
601
return self.attempt_lock()
602
394
except LockContention:
603
# possibly report the blockage, then try again
605
# TODO: In a few cases, we find out that there's contention by
606
# reading the held info and observing that it's not ours. In
607
# those cases it's a bit redundant to read it again. However,
608
# the normal case (??) is that the rename fails and so we
609
# don't know who holds the lock. For simplicity we peek
611
396
new_info = self.peek()
397
mutter('last_info: %s, new info: %s', last_info, new_info)
612
398
if new_info is not None and new_info != last_info:
613
399
if last_info is None:
614
400
start = 'Unable to obtain'
616
402
start = 'Lock owner changed for'
617
403
last_info = new_info
618
msg = u'%s lock %s %s.' % (start, lock_url, new_info)
404
formatted_info = self._format_lock_info(new_info)
619
405
if deadline_str is None:
620
406
deadline_str = time.strftime('%H:%M:%S',
621
time.localtime(deadline))
623
msg += ('\nWill continue to try until %s, unless '
626
msg += '\nSee "bzr help break-lock" for more.'
627
self._report_function(msg)
628
if (max_attempts is not None) and (attempt_count >= max_attempts):
629
self._trace("exceeded %d attempts")
630
raise LockContention(self)
407
time.localtime(deadline))
408
self._report_function('%s %s\n'
410
'%s\n' # locked ... ago
411
'Will continue to try until %s\n',
631
418
if time.time() + poll < deadline:
632
self._trace("waiting %ss", poll)
635
# As timeout is always 0 for remote locks
636
# this block is applicable only for local
638
self._trace("timeout after waiting %ss", timeout)
639
raise LockContention('(local)', lock_url)
421
raise LockContention(self)
641
423
def leave_in_place(self):
642
424
self._locked_via_token = True
668
450
self._locked_via_token = True
671
return self.wait_lock()
454
return self.peek().get('nonce')
673
456
def lock_read(self):
674
457
"""Compatibility-mode shared lock.
676
LockDir doesn't support shared read-only locks, so this
459
LockDir doesn't support shared read-only locks, so this
677
460
just pretends that the lock is taken but really does nothing.
679
# At the moment Branches are commonly locked for read, but
462
# At the moment Branches are commonly locked for read, but
680
463
# we can't rely on that remotely. Once this is cleaned up,
681
# reenable this warning to prevent it coming back in
464
# reenable this warning to prevent it coming back in
682
465
# -- mbp 20060303
683
466
## warn("LockDir.lock_read falls back to write lock")
684
467
if self._lock_held or self._fake_read_lock:
685
468
raise LockContention(self)
686
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)
484
def _format_lock_info(self, info):
485
"""Turn the contents of peek() into something for the user"""
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),),
688
494
def validate_token(self, token):
689
495
if token is not None:
690
496
info = self.peek()
695
501
lock_token = info.get('nonce')
696
502
if token != lock_token:
697
503
raise errors.TokenMismatch(token, lock_token)
699
self._trace("revalidated by token %r", token)
701
def _trace(self, format, *args):
702
if 'lock' not in debug.debug_flags:
704
mutter(str(self) + ": " + (format % args))
706
def get_config(self):
707
"""Get the configuration that governs this lockdir."""
708
# XXX: This really should also use the locationconfig at least, but
709
# that seems a bit hard to hook up at the moment. -- mbp 20110329
710
# FIXME: The above is still true ;) -- vila 20110811
711
return config.GlobalStack()
714
class LockHeldInfo(object):
715
"""The information recorded about a held lock.
717
This information is recorded into the lock when it's taken, and it can be
718
read back by any process with access to the lockdir. It can be used, for
719
example, to tell the user who holds the lock, or to try to detect whether
720
the lock holder is still alive.
722
Prior to bzr 2.4 a simple dict was used instead of an object.
725
def __init__(self, info_dict):
726
self.info_dict = info_dict
729
"""Return a debugging representation of this object."""
730
return "%s(%r)" % (self.__class__.__name__, self.info_dict)
732
def __unicode__(self):
733
"""Return a user-oriented description of this object."""
734
d = self.to_readable_dict()
736
u'held by %(user)s on %(hostname)s (process #%(pid)s), '
737
u'acquired %(time_ago)s' % d)
739
def to_readable_dict(self):
740
"""Turn the holder info into a dict of human-readable attributes.
742
For example, the start time is presented relative to the current time,
743
rather than as seconds since the epoch.
745
Returns a list of [user, hostname, pid, time_ago] all as readable
748
start_time = self.info_dict.get('start_time')
749
if start_time is None:
750
time_ago = '(unknown)'
752
time_ago = format_delta(
753
time.time() - int(self.info_dict['start_time']))
754
user = self.info_dict.get('user', '<unknown>')
755
hostname = self.info_dict.get('hostname', '<unknown>')
756
pid = self.info_dict.get('pid', '<unknown>')
763
def get(self, field_name):
764
"""Return the contents of a field from the lock info, or None."""
765
return self.info_dict.get(field_name)
768
def for_this_process(cls, extra_holder_info):
769
"""Return a new LockHeldInfo for a lock taken by this process.
772
hostname=get_host_name(),
773
pid=str(os.getpid()),
774
nonce=rand_chars(20),
775
start_time=str(int(time.time())),
776
user=get_username_for_lock_info(),
778
if extra_holder_info is not None:
779
info.update(extra_holder_info)
783
s = rio.Stanza(**self.info_dict)
787
def from_info_file_bytes(cls, info_file_bytes):
788
"""Construct from the contents of the held file."""
789
lines = osutils.split_lines(info_file_bytes)
791
stanza = rio.read_stanza(lines)
792
except ValueError, e:
793
mutter('Corrupt lock info file: %r', lines)
794
raise LockCorrupt("could not parse lock info file: " + str(e),
797
# see bug 185013; we fairly often end up with the info file being
798
# empty after an interruption; we could log a message here but
799
# there may not be much we can say
802
return cls(stanza.as_dict())
804
def __cmp__(self, other):
805
"""Value comparison of lock holders."""
807
cmp(type(self), type(other))
808
or cmp(self.info_dict, other.info_dict))
810
def is_locked_by_this_process(self):
811
"""True if this process seems to be the current lock holder."""
813
self.get('hostname') == get_host_name()
814
and self.get('pid') == str(os.getpid())
815
and self.get('user') == get_username_for_lock_info())
817
def is_lock_holder_known_dead(self):
818
"""True if the lock holder process is known to be dead.
820
False if it's either known to be still alive, or if we just can't tell.
822
We can be fairly sure the lock holder is dead if it declared the same
823
hostname and there is no process with the given pid alive. If people
824
have multiple machines with the same hostname this may cause trouble.
826
This doesn't check whether the lock holder is in fact the same process
827
calling this method. (In that case it will return true.)
829
if self.get('hostname') != get_host_name():
831
if self.get('hostname') == 'localhost':
834
if self.get('user') != get_username_for_lock_info():
835
# Could well be another local process by a different user, but
836
# just to be safe we won't conclude about this either.
838
pid_str = self.info_dict.get('pid', None)
840
mutter("no pid recorded in %r" % (self, ))
845
mutter("can't parse pid %r from %r"
848
return osutils.is_local_pid_dead(pid)
851
def get_username_for_lock_info():
852
"""Get a username suitable for putting into a lock.
854
It's ok if what's written here is not a proper email address as long
855
as it gives some clue who the user is.
858
return config.GlobalConfig().username()
859
except errors.NoWhoami:
860
return osutils.getuser_unicode()
added
removed
bzrlib/lockdir.py
