107
103
# the existing locking code and needs a new format of the containing object.
108
104
# -- robertc, mbp 20070628
108
from cStringIO import StringIO
114
110
from bzrlib import (
123
from bzrlib.decorators import only_raises
124
115
from bzrlib.errors import (
125
116
DirectoryNotEmpty,
127
118
LockBreakMismatch,
138
127
from bzrlib.trace import mutter, note
139
from bzrlib.osutils import format_delta, rand_chars, get_host_name
128
from bzrlib.transport import Transport
129
from bzrlib.osutils import rand_chars, format_delta
130
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
134
# XXX: At the moment there is no consideration of thread safety on LockDir
147
135
# objects. This should perhaps be updated - e.g. if two threads try to take a
158
146
# files/dirs created.
161
_DEFAULT_TIMEOUT_SECONDS = 30
149
_DEFAULT_TIMEOUT_SECONDS = 300
162
150
_DEFAULT_POLL_SECONDS = 1.0
165
class LockDir(lock.Lock):
166
"""Write-lock guarding access to data.
153
class LockDir(object):
154
"""Write-lock guarding access to data."""
169
156
__INFO_NAME = '/info'
171
def __init__(self, transport, path, file_modebits=0644, dir_modebits=0755,
172
extra_holder_info=None):
158
def __init__(self, transport, path, file_modebits=0644, dir_modebits=0755):
173
159
"""Create a new LockDir object.
175
161
The LockDir is initially unlocked - this just creates the object.
177
163
:param transport: Transport which will contain the lock
179
:param path: Path to the lock within the base directory of the
165
:param path: Path to the lock within the base directory of the
182
:param extra_holder_info: If passed, {str:str} dict of extra or
183
updated information to insert into the info file when the lock is
168
assert isinstance(transport, Transport), \
169
("not a transport: %r" % transport)
186
170
self.transport = transport
188
172
self._lock_held = False
206
189
def create(self, mode=None):
207
190
"""Create the on-disk lock.
209
This is typically only called when the object/directory containing the
192
This is typically only called when the object/directory containing the
210
193
directory is first created. The lock is not held when it's created.
195
if self.transport.is_readonly():
196
raise UnlockableTransport(self.transport)
212
197
self._trace("create lock directory")
214
self.transport.mkdir(self.path, mode=mode)
215
except (TransportError, PathError), e:
216
raise LockFailed(self, e)
198
self.transport.mkdir(self.path, mode=mode)
218
200
def _attempt_lock(self):
219
201
"""Make the pending directory and attempt to rename into place.
221
203
If the rename succeeds, we read back the info file to check that we
222
204
really got the lock.
228
210
: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.
212
:raises LockContention: If the lock is held by someone else. The exception
213
contains the info of the current holder of the lock.
233
215
self._trace("lock_write...")
234
216
start_time = time.time()
217
tmpname = self._create_pending_dir()
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)
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)
219
self.transport.rename(tmpname, self._held_dir)
220
except (PathError, DirectoryNotEmpty, FileExists, ResourceBusy), e:
221
self._trace("... contention, %s", e)
222
self._remove_pending_dir(tmpname)
223
raise LockContention(self)
225
self._trace("... lock failed, %s", e)
226
self._remove_pending_dir(tmpname)
258
228
# We must check we really got the lock, because Launchpad's sftp
259
229
# server at one time had a bug were the rename would successfully
260
230
# move the new directory into the existing directory, which was
261
231
# incorrect. It's possible some other servers or filesystems will
262
232
# have a similar bug allowing someone to think they got the lock
263
233
# 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.
269
234
info = self.peek()
270
235
self._trace("after locking, info=%r", info)
272
raise LockFailed(self, "lock was renamed into place, but "
274
if info.get('nonce') != self.nonce:
236
if info['nonce'] != self.nonce:
275
237
self._trace("rename succeeded, "
276
238
"but lock is still held by someone else")
277
239
raise LockContention(self)
280
242
(time.time() - start_time) * 1000)
281
243
return self.nonce
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_user_option_as_bool(
301
ui.ui_factory.show_user_warning(
303
lock_url=urlutils.join(self.transport.base, self.path),
304
other_holder_info=unicode(other_holder))
305
self.force_break(other_holder)
306
self._trace("stole lock from dead holder")
308
raise LockContention(self)
310
245
def _remove_pending_dir(self, tmpname):
311
246
"""Remove the pending directory
313
This is called if we failed to rename into place, so that the pending
248
This is called if we failed to rename into place, so that the pending
314
249
dirs don't clutter up the lockdir.
316
251
self._trace("remove %s", tmpname)
381
314
self.transport.delete_tree(tmpname)
382
315
self._trace("... unlock succeeded after %dms",
383
316
(time.time() - start_time) * 1000)
384
result = lock.LockResult(self.transport.abspath(self.path),
386
for hook in self.hooks['lock_released']:
389
318
def break_lock(self):
390
319
"""Break a lock not held by this instance of LockDir.
392
This is a UI centric function: it uses the ui.ui_factory to
321
This is a UI centric function: it uses the bzrlib.ui.ui_factory to
393
322
prompt for input if a lock is detected and there is any doubt about
394
it possibly being still active. force_break is the non-interactive
397
:returns: LockResult for the broken lock.
323
it possibly being still active.
399
325
self._check_not_locked()
401
holder_info = self.peek()
402
except LockCorrupt, e:
403
# The lock info is corrupt.
404
if ui.ui_factory.get_boolean(u"Break (corrupt %r)" % (self,)):
405
self.force_break_corrupt(e.file_data)
326
holder_info = self.peek()
407
327
if holder_info is not None:
408
if ui.ui_factory.confirm_action(
409
u"Break %(lock_info)s",
410
'bzrlib.lockdir.break',
411
dict(lock_info=unicode(holder_info))):
412
result = self.force_break(holder_info)
413
ui.ui_factory.show_message(
414
"Broke lock %s" % result.lock_url)
328
lock_info = '\n'.join(self._format_lock_info(holder_info))
329
if bzrlib.ui.ui_factory.get_boolean("Break %s" % lock_info):
330
self.force_break(holder_info)
416
332
def force_break(self, dead_holder_info):
417
333
"""Release a lock held by another process.
420
336
it still thinks it has the lock there will be two concurrent writers.
421
337
In general the user's approval should be sought for lock breaks.
339
dead_holder_info must be the result of a previous LockDir.peek() call;
340
this is used to check that it's still held by the same process that
341
the user decided was dead. If this is not the current holder,
342
LockBreakMismatch is raised.
423
344
After the lock is broken it will not be held by any process.
424
It is possible that another process may sneak in and take the
345
It is possible that another process may sneak in and take the
425
346
lock before the breaking process acquires it.
427
:param dead_holder_info:
428
Must be the result of a previous LockDir.peek() call; this is used
429
to check that it's still held by the same process that the user
430
decided was dead. If this is not the current holder,
431
LockBreakMismatch is raised.
433
:returns: LockResult for the broken lock.
435
if not isinstance(dead_holder_info, LockHeldInfo):
348
if not isinstance(dead_holder_info, dict):
436
349
raise ValueError("dead_holder_info: %r" % dead_holder_info)
437
350
self._check_not_locked()
438
351
current_info = self.peek()
452
365
raise LockBreakMismatch(self, broken_info, dead_holder_info)
453
366
self.transport.delete(broken_info_path)
454
367
self.transport.rmdir(tmpname)
455
result = lock.LockResult(self.transport.abspath(self.path),
456
current_info.get('nonce'))
457
for hook in self.hooks['lock_broken']:
461
def force_break_corrupt(self, corrupt_info_lines):
462
"""Release a lock that has been corrupted.
464
This is very similar to force_break, it except it doesn't assume that
465
self.peek() can work.
467
:param corrupt_info_lines: the lines of the corrupted info file, used
468
to check that the lock hasn't changed between reading the (corrupt)
469
info file and calling force_break_corrupt.
471
# XXX: this copes with unparseable info files, but what about missing
472
# info files? Or missing lock dirs?
473
self._check_not_locked()
474
tmpname = '%s/broken.%s.tmp' % (self.path, rand_chars(20))
475
self.transport.rename(self._held_dir, tmpname)
476
# check that we actually broke the right lock, not someone else;
477
# there's a small race window between checking it and doing the
479
broken_info_path = tmpname + self.__INFO_NAME
480
broken_content = self.transport.get_bytes(broken_info_path)
481
broken_lines = osutils.split_lines(broken_content)
482
if broken_lines != corrupt_info_lines:
483
raise LockBreakMismatch(self, broken_lines, corrupt_info_lines)
484
self.transport.delete(broken_info_path)
485
self.transport.rmdir(tmpname)
486
result = lock.LockResult(self.transport.abspath(self.path))
487
for hook in self.hooks['lock_broken']:
490
369
def _check_not_locked(self):
491
370
"""If the lock is held by this instance, raise an error."""
511
390
if info.get('nonce') != self.nonce:
512
391
# there is a lock, but not ours
513
392
raise LockBroken(self)
515
394
def _read_info_file(self, path):
516
395
"""Read one given info file.
518
397
peek() reads the info file of the lock holder, if any.
520
return LockHeldInfo.from_info_file_bytes(
521
self.transport.get_bytes(path))
399
return self._parse_info(self.transport.get(path))
524
402
"""Check if the lock is held by anyone.
526
If it is held, this returns the lock info structure as a dict
404
If it is held, this returns the lock info structure as a rio Stanza,
527
405
which contains some information about the current lock holder.
528
406
Otherwise returns None.
531
409
info = self._read_info_file(self._held_info_path)
532
410
self._trace("peek -> held")
411
assert isinstance(info, dict), \
412
"bad parse result %r" % info
534
414
except NoSuchFile, e:
535
415
self._trace("peek -> not held")
550
447
if self._fake_read_lock:
551
448
raise LockContention(self)
552
result = self._attempt_lock()
553
hook_result = lock.LockResult(self.transport.abspath(self.path),
555
for hook in self.hooks['lock_acquired']:
559
def lock_url_for_display(self):
560
"""Give a nicely-printable representation of the URL of this lock."""
561
# As local lock urls are correct we display them.
562
# We avoid displaying remote lock urls.
563
lock_url = self.transport.abspath(self.path)
564
if lock_url.startswith('file://'):
565
lock_url = lock_url.split('.bzr/')[0]
449
if self.transport.is_readonly():
450
raise UnlockableTransport(self.transport)
451
return self._attempt_lock()
570
453
def wait_lock(self, timeout=None, poll=None, max_attempts=None):
571
454
"""Wait a certain period for a lock.
675
558
def lock_read(self):
676
559
"""Compatibility-mode shared lock.
678
LockDir doesn't support shared read-only locks, so this
561
LockDir doesn't support shared read-only locks, so this
679
562
just pretends that the lock is taken but really does nothing.
681
# At the moment Branches are commonly locked for read, but
564
# At the moment Branches are commonly locked for read, but
682
565
# we can't rely on that remotely. Once this is cleaned up,
683
# reenable this warning to prevent it coming back in
566
# reenable this warning to prevent it coming back in
684
567
# -- mbp 20060303
685
568
## warn("LockDir.lock_read falls back to write lock")
686
569
if self._lock_held or self._fake_read_lock:
687
570
raise LockContention(self)
688
571
self._fake_read_lock = True
573
def _format_lock_info(self, info):
574
"""Turn the contents of peek() into something for the user"""
575
lock_url = self.transport.abspath(self.path)
576
delta = time.time() - int(info['start_time'])
578
'lock %s' % (lock_url,),
579
'held by %(user)s on host %(hostname)s [process #%(pid)s]' % info,
580
'locked %s' % (format_delta(delta),),
690
583
def validate_token(self, token):
691
584
if token is not None:
692
585
info = self.peek()
704
597
if 'lock' not in debug.debug_flags:
706
599
mutter(str(self) + ": " + (format % args))
708
def get_config(self):
709
"""Get the configuration that governs this lockdir."""
710
# XXX: This really should also use the locationconfig at least, but
711
# that seems a bit hard to hook up at the moment. -- mbp 20110329
712
return config.GlobalConfig()
715
class LockHeldInfo(object):
716
"""The information recorded about a held lock.
718
This information is recorded into the lock when it's taken, and it can be
719
read back by any process with access to the lockdir. It can be used, for
720
example, to tell the user who holds the lock, or to try to detect whether
721
the lock holder is still alive.
723
Prior to bzr 2.4 a simple dict was used instead of an object.
726
def __init__(self, info_dict):
727
self.info_dict = info_dict
730
"""Return a debugging representation of this object."""
731
return "%s(%r)" % (self.__class__.__name__, self.info_dict)
733
def __unicode__(self):
734
"""Return a user-oriented description of this object."""
735
d = self.to_readable_dict()
737
u'held by %(user)s on %(hostname)s (process #%(pid)s), '
738
u'acquired %(time_ago)s' % d)
740
def to_readable_dict(self):
741
"""Turn the holder info into a dict of human-readable attributes.
743
For example, the start time is presented relative to the current time,
744
rather than as seconds since the epoch.
746
Returns a list of [user, hostname, pid, time_ago] all as readable
749
start_time = self.info_dict.get('start_time')
750
if start_time is None:
751
time_ago = '(unknown)'
753
time_ago = format_delta(
754
time.time() - int(self.info_dict['start_time']))
755
user = self.info_dict.get('user', '<unknown>')
756
hostname = self.info_dict.get('hostname', '<unknown>')
757
pid = self.info_dict.get('pid', '<unknown>')
764
def get(self, field_name):
765
"""Return the contents of a field from the lock info, or None."""
766
return self.info_dict.get(field_name)
769
def for_this_process(cls, extra_holder_info):
770
"""Return a new LockHeldInfo for a lock taken by this process.
773
hostname=get_host_name(),
774
pid=str(os.getpid()),
775
nonce=rand_chars(20),
776
start_time=str(int(time.time())),
777
user=get_username_for_lock_info(),
779
if extra_holder_info is not None:
780
info.update(extra_holder_info)
784
s = rio.Stanza(**self.info_dict)
788
def from_info_file_bytes(cls, info_file_bytes):
789
"""Construct from the contents of the held file."""
790
lines = osutils.split_lines(info_file_bytes)
792
stanza = rio.read_stanza(lines)
793
except ValueError, e:
794
mutter('Corrupt lock info file: %r', lines)
795
raise LockCorrupt("could not parse lock info file: " + str(e),
798
# see bug 185013; we fairly often end up with the info file being
799
# empty after an interruption; we could log a message here but
800
# there may not be much we can say
803
return cls(stanza.as_dict())
805
def __cmp__(self, other):
806
"""Value comparison of lock holders."""
808
cmp(type(self), type(other))
809
or cmp(self.info_dict, other.info_dict))
811
def is_locked_by_this_process(self):
812
"""True if this process seems to be the current lock holder."""
814
self.get('hostname') == get_host_name()
815
and self.get('pid') == str(os.getpid())
816
and self.get('user') == get_username_for_lock_info())
818
def is_lock_holder_known_dead(self):
819
"""True if the lock holder process is known to be dead.
821
False if it's either known to be still alive, or if we just can't tell.
823
We can be fairly sure the lock holder is dead if it declared the same
824
hostname and there is no process with the given pid alive. If people
825
have multiple machines with the same hostname this may cause trouble.
827
This doesn't check whether the lock holder is in fact the same process
828
calling this method. (In that case it will return true.)
830
if self.get('hostname') != get_host_name():
832
if self.get('hostname') == 'localhost':
835
if self.get('user') != get_username_for_lock_info():
836
# Could well be another local process by a different user, but
837
# just to be safe we won't conclude about this either.
839
pid_str = self.info_dict.get('pid', None)
841
mutter("no pid recorded in %r" % (self, ))
846
mutter("can't parse pid %r from %r"
849
return osutils.is_local_pid_dead(pid)
852
def get_username_for_lock_info():
853
"""Get a username suitable for putting into a lock.
855
It's ok if what's written here is not a proper email address as long
856
as it gives some clue who the user is.
859
return config.GlobalConfig().username()
860
except errors.NoWhoami:
861
return osutils.getuser_unicode()
added
removed
bzrlib/lockdir.py
