87
87
>>> # typically will be obtained from a BzrDir, Branch, etc
88
88
>>> t = MemoryTransport()
89
89
>>> l = LockDir(t, 'sample-lock')
91
>>> token = l.wait_lock()
92
91
>>> # 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
98
from StringIO import StringIO
115
100
import bzrlib.config
116
from bzrlib.decorators import only_raises
117
101
from bzrlib.errors import (
118
102
DirectoryNotEmpty,
120
104
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
112
from bzrlib.transport import Transport
113
from bzrlib.osutils import rand_chars
114
from bzrlib.rio import RioWriter, read_stanza, Stanza
139
116
# XXX: At the moment there is no consideration of thread safety on LockDir
140
117
# objects. This should perhaps be updated - e.g. if two threads try to take a
141
118
# lock at the same time they should *both* get it. But then that's unlikely
142
119
# to be a good idea.
121
# TODO: Transport could offer a simpler put() method that avoids the
122
# rename-into-place for cases like creating the lock template, where there is
123
# no chance that the file already exists.
144
125
# TODO: Perhaps store some kind of note like the bzr command line in the lock
147
128
# TODO: Some kind of callback run while polling a lock to show progress
150
# TODO: Make sure to pass the right file and directory mode bits to all
151
# files/dirs created.
154
131
_DEFAULT_TIMEOUT_SECONDS = 300
155
_DEFAULT_POLL_SECONDS = 1.0
158
class LockDir(lock.Lock):
159
"""Write-lock guarding access to data.
132
_DEFAULT_POLL_SECONDS = 0.5
134
class LockDir(object):
135
"""Write-lock guarding access to data."""
162
137
__INFO_NAME = '/info'
164
def __init__(self, transport, path, file_modebits=0644, dir_modebits=0755):
139
def __init__(self, transport, path):
165
140
"""Create a new LockDir object.
167
142
The LockDir is initially unlocked - this just creates the object.
169
144
:param transport: Transport which will contain the lock
171
:param path: Path to the lock within the base directory of the
146
:param path: Path to the lock within the base directory of the
149
assert isinstance(transport, Transport), \
150
("not a transport: %r" % transport)
174
151
self.transport = transport
176
153
self._lock_held = False
177
self._locked_via_token = False
178
self._fake_read_lock = False
179
self._held_dir = path + '/held'
180
self._held_info_path = self._held_dir + self.__INFO_NAME
181
self._file_modebits = file_modebits
182
self._dir_modebits = dir_modebits
184
self._report_function = note
154
self._info_path = path + self.__INFO_NAME
155
self.nonce = rand_chars(20)
186
157
def __repr__(self):
187
158
return '%s(%s%s)' % (self.__class__.__name__,
191
162
is_held = property(lambda self: self._lock_held)
193
def create(self, mode=None):
194
"""Create the on-disk lock.
196
This is typically only called when the object/directory containing the
197
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.
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)
229
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.edge.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)
164
def attempt_lock(self):
165
"""Take the lock; fail if it's already held.
167
If you wish to block until the lock can be obtained, call wait_lock()
170
if self.transport.is_readonly():
171
raise UnlockableTransport(self.transport)
173
tmpname = '%s.pending.%s.tmp' % (self.path, rand_chars(20))
174
self.transport.mkdir(tmpname)
176
self._prepare_info(sio)
178
self.transport.put(tmpname + self.__INFO_NAME, sio)
179
# FIXME: this turns into os.rename on posix, but into a fancy rename
180
# on Windows that may overwrite existing directory trees.
181
# NB: posix rename will overwrite empty directories, but not
182
# non-empty directories.
183
self.transport.move(tmpname, self.path)
184
self._lock_held = True
187
except (DirectoryNotEmpty, FileExists), e:
189
# fall through to here on contention
190
raise LockContention(self)
300
192
def unlock(self):
301
193
"""Release a held lock
303
if self._fake_read_lock:
304
self._fake_read_lock = False
306
195
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']:
343
def break_lock(self):
344
"""Break a lock not held by this instance of LockDir.
346
This is a UI centric function: it uses the bzrlib.ui.ui_factory to
347
prompt for input if a lock is detected and there is any doubt about
348
it possibly being still active.
350
self._check_not_locked()
351
holder_info = self.peek()
352
if holder_info is not None:
353
lock_info = '\n'.join(self._format_lock_info(holder_info))
354
if bzrlib.ui.ui_factory.get_boolean("Break %s" % lock_info):
355
self.force_break(holder_info)
196
raise LockNotHeld(self)
197
# rename before deleting, because we can't atomically remove the whole
199
tmpname = '%s.releasing.%s.tmp' % (self.path, rand_chars(20))
200
self.transport.rename(self.path, tmpname)
201
self._lock_held = False
202
self.transport.delete(tmpname + self.__INFO_NAME)
203
self.transport.rmdir(tmpname)
357
205
def force_break(self, dead_holder_info):
358
206
"""Release a lock held by another process.
419
259
if info.get('nonce') != self.nonce:
420
260
# there is a lock, but not ours
421
261
raise LockBroken(self)
423
263
def _read_info_file(self, path):
424
"""Read one given info file.
426
peek() reads the info file of the lock holder, if any.
428
return self._parse_info(self.transport.get_bytes(path))
264
return self._parse_info(self.transport.get(path))
431
267
"""Check if the lock is held by anyone.
433
If it is held, this returns the lock info structure as a dict
269
If it is held, this returns the lock info structure as a rio Stanza,
434
270
which contains some information about the current lock holder.
435
271
Otherwise returns None.
438
info = self._read_info_file(self._held_info_path)
439
self._trace("peek -> held")
274
info = self._read_info_file(self._info_path)
275
assert isinstance(info, dict), \
276
"bad parse result %r" % info
441
278
except NoSuchFile, e:
442
self._trace("peek -> not held")
444
def _prepare_info(self):
281
def _prepare_info(self, outf):
445
282
"""Write information about a pending lock to a temporary file.
447
285
# XXX: is creating this here inefficient?
448
286
config = bzrlib.config.GlobalConfig()
450
user = config.user_email()
451
except errors.NoEmailInUsername:
452
user = config.username()
453
s = rio.Stanza(hostname=get_host_name(),
287
s = Stanza(hostname=socket.gethostname(),
454
288
pid=str(os.getpid()),
455
289
start_time=str(int(time.time())),
456
290
nonce=self.nonce,
291
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):
293
RioWriter(outf).write_stanza(s)
295
def _parse_info(self, info_file):
296
return read_stanza(info_file.readlines()).as_dict()
298
def wait_lock(self, timeout=_DEFAULT_TIMEOUT_SECONDS,
299
poll=_DEFAULT_POLL_SECONDS):
490
300
"""Wait a certain period for a lock.
492
302
If the lock can be acquired within the bounded time, it
494
304
is raised. Either way, this function should return within
495
305
approximately `timeout` seconds. (It may be a bit more if
496
306
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.
308
# XXX: the transport interface doesn't let us guard
309
# against operations there taking a long time.
514
310
deadline = time.time() + timeout
521
return self.attempt_lock()
522
315
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
lock_url = self.transport.abspath(self.path)
543
# See <https://bugs.edge.launchpad.net/bzr/+bug/250451>
544
# the URL here is sometimes not one that is useful to the
545
# user, perhaps being wrapped in a lp-%d or chroot decorator,
546
# especially if this error is issued from the server.
547
self._report_function('%s %s\n'
549
'%s\n' # locked ... ago
550
'Will continue to try until %s, unless '
551
'you press Ctrl-C.\n'
552
'See "bzr help break-lock" for more.',
560
if (max_attempts is not None) and (attempt_count >= max_attempts):
561
self._trace("exceeded %d attempts")
562
raise LockContention(self)
563
if time.time() + poll < deadline:
564
self._trace("waiting %ss", poll)
567
self._trace("timeout after waiting %ss", timeout)
568
raise LockContention(self)
570
def leave_in_place(self):
571
self._locked_via_token = True
573
def dont_leave_in_place(self):
574
self._locked_via_token = False
576
def lock_write(self, token=None):
577
"""Wait for and acquire the lock.
579
:param token: if this is already locked, then lock_write will fail
580
unless the token matches the existing lock.
581
:returns: a token if this instance supports tokens, otherwise None.
582
:raises TokenLockingNotSupported: when a token is given but this
583
instance doesn't support using token locks.
584
:raises MismatchedToken: if the specified token doesn't match the token
585
of the existing lock.
587
A token should be passed in if you know that you have locked the object
588
some other way, and need to synchronise this object's state with that
591
XXX: docstring duplicated from LockableFiles.lock_write.
593
if token is not None:
594
self.validate_token(token)
596
self._lock_held = True
597
self._locked_via_token = True
600
return self.wait_lock()
603
"""Compatibility-mode shared lock.
605
LockDir doesn't support shared read-only locks, so this
606
just pretends that the lock is taken but really does nothing.
608
# At the moment Branches are commonly locked for read, but
609
# we can't rely on that remotely. Once this is cleaned up,
610
# reenable this warning to prevent it coming back in
612
## warn("LockDir.lock_read falls back to write lock")
613
if self._lock_held or self._fake_read_lock:
614
raise LockContention(self)
615
self._fake_read_lock = True
617
def _format_lock_info(self, info):
618
"""Turn the contents of peek() into something for the user"""
619
lock_url = self.transport.abspath(self.path)
620
start_time = info.get('start_time')
621
if start_time is None:
622
time_ago = '(unknown)'
624
time_ago = format_delta(time.time() - int(info['start_time']))
626
'lock %s' % (lock_url,),
627
'held by %s on host %s [process #%s]' %
628
tuple([info.get(x, '<unknown>') for x in ['user', 'hostname', 'pid']]),
629
'locked %s' % (time_ago,),
632
def validate_token(self, token):
633
if token is not None:
639
lock_token = info.get('nonce')
640
if token != lock_token:
641
raise errors.TokenMismatch(token, lock_token)
643
self._trace("revalidated by token %r", token)
645
def _trace(self, format, *args):
646
if 'lock' not in debug.debug_flags:
648
mutter(str(self) + ": " + (format % args))
317
if time.time() + poll < deadline:
320
raise LockContention(self)
322
def wait(self, timeout=20, poll=0.5):
323
"""Wait a certain period for a lock to be released."""
324
# XXX: the transport interface doesn't let us guard
325
# against operations there taking a long time.
326
deadline = time.time() + timeout
330
if time.time() + poll < deadline:
333
raise LockContention(self)
added
removed
bzrlib/lockdir.py
