118
105
LockBreakMismatch,
128
from bzrlib.hooks import Hooks
129
from bzrlib.trace import mutter, note
130
from bzrlib.osutils import format_delta, rand_chars, get_host_name
133
from bzrlib.lazy_import import lazy_import
134
lazy_import(globals(), """
135
from bzrlib import rio
113
from bzrlib.transport import Transport
114
from bzrlib.osutils import rand_chars
115
from bzrlib.rio import RioWriter, read_stanza, Stanza
138
117
# XXX: At the moment there is no consideration of thread safety on LockDir
139
118
# objects. This should perhaps be updated - e.g. if two threads try to take a
140
119
# lock at the same time they should *both* get it. But then that's unlikely
141
120
# to be a good idea.
122
# TODO: Transport could offer a simpler put() method that avoids the
123
# rename-into-place for cases like creating the lock template, where there is
124
# no chance that the file already exists.
143
126
# TODO: Perhaps store some kind of note like the bzr command line in the lock
146
129
# TODO: Some kind of callback run while polling a lock to show progress
149
# TODO: Make sure to pass the right file and directory mode bits to all
150
# files/dirs created.
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# TODO: perhaps put everything (held, pending, releasing, broken) inside a
133
# top-level directory with the name of the lock, so that we can still see the
134
# lock actually exists -- the top-level directory can then be created only by
153
137
_DEFAULT_TIMEOUT_SECONDS = 300
154
_DEFAULT_POLL_SECONDS = 1.0
157
class LockDir(lock.Lock):
158
"""Write-lock guarding access to data.
138
_DEFAULT_POLL_SECONDS = 0.5
140
class LockDir(object):
141
"""Write-lock guarding access to data."""
161
143
__INFO_NAME = '/info'
163
def __init__(self, transport, path, file_modebits=0644, dir_modebits=0755):
145
def __init__(self, transport, path):
164
146
"""Create a new LockDir object.
166
148
The LockDir is initially unlocked - this just creates the object.
190
168
is_held = property(lambda self: self._lock_held)
192
def create(self, mode=None):
193
"""Create the on-disk lock.
195
This is typically only called when the object/directory containing the
196
directory is first created. The lock is not held when it's created.
198
self._trace("create lock directory")
200
self.transport.mkdir(self.path, mode=mode)
201
except (TransportError, PathError), e:
202
raise LockFailed(self, e)
205
def _attempt_lock(self):
206
"""Make the pending directory and attempt to rename into place.
170
def attempt_lock(self):
171
"""Take the lock; fail if it's already held.
208
If the rename succeeds, we read back the info file to check that we
211
If we fail to acquire the lock, this method is responsible for
212
cleaning up the pending directory if possible. (But it doesn't do
215
:returns: The nonce of the lock, if it was successfully acquired.
217
:raises LockContention: If the lock is held by someone else. The exception
218
contains the info of the current holder of the lock.
220
self._trace("lock_write...")
221
start_time = time.time()
223
tmpname = self._create_pending_dir()
224
except (errors.TransportError, PathError), e:
225
self._trace("... failed to create pending dir, %s", e)
226
raise LockFailed(self, e)
228
self.transport.rename(tmpname, self._held_dir)
229
except (errors.TransportError, PathError, DirectoryNotEmpty,
230
FileExists, ResourceBusy), e:
231
self._trace("... contention, %s", e)
232
self._remove_pending_dir(tmpname)
233
raise LockContention(self)
235
self._trace("... lock failed, %s", e)
236
self._remove_pending_dir(tmpname)
238
# We must check we really got the lock, because Launchpad's sftp
239
# server at one time had a bug were the rename would successfully
240
# move the new directory into the existing directory, which was
241
# incorrect. It's possible some other servers or filesystems will
242
# have a similar bug allowing someone to think they got the lock
243
# when it's already held.
245
self._trace("after locking, info=%r", info)
246
if info['nonce'] != self.nonce:
247
self._trace("rename succeeded, "
248
"but lock is still held by someone else")
249
raise LockContention(self)
250
self._lock_held = True
251
self._trace("... lock succeeded after %dms",
252
(time.time() - start_time) * 1000)
255
def _remove_pending_dir(self, tmpname):
256
"""Remove the pending directory
258
This is called if we failed to rename into place, so that the pending
259
dirs don't clutter up the lockdir.
261
self._trace("remove %s", tmpname)
263
self.transport.delete(tmpname + self.__INFO_NAME)
264
self.transport.rmdir(tmpname)
266
note("error removing pending lock: %s", e)
268
def _create_pending_dir(self):
269
tmpname = '%s/%s.tmp' % (self.path, rand_chars(10))
271
self.transport.mkdir(tmpname)
273
# This may raise a FileExists exception
274
# which is okay, it will be caught later and determined
275
# to be a LockContention.
276
self._trace("lock directory does not exist, creating it")
277
self.create(mode=self._dir_modebits)
278
# After creating the lock directory, try again
279
self.transport.mkdir(tmpname)
280
self.nonce = rand_chars(20)
281
info_bytes = self._prepare_info()
282
# We use put_file_non_atomic because we just created a new unique
283
# directory so we don't have to worry about files existing there.
284
# We'll rename the whole directory into place to get atomic
286
self.transport.put_bytes_non_atomic(tmpname + self.__INFO_NAME,
173
If you wish to block until the lock can be obtained, call wait_lock()
176
if self.transport.is_readonly():
177
raise UnlockableTransport(self.transport)
179
tmpname = '%s.pending.%s.tmp' % (self.path, rand_chars(20))
180
self.transport.mkdir(tmpname)
182
self._prepare_info(sio)
184
self.transport.put(tmpname + self.__INFO_NAME, sio)
185
# FIXME: this turns into os.rename on posix, but into a fancy rename
186
# on Windows that may overwrite existing directory trees.
187
# NB: posix rename will overwrite empty directories, but not
188
# non-empty directories.
189
self.transport.move(tmpname, self.path)
190
self._lock_held = True
193
except (DirectoryNotEmpty, FileExists), e:
195
# fall through to here on contention
196
raise LockContention(self)
290
198
def unlock(self):
291
199
"""Release a held lock
293
if self._fake_read_lock:
294
self._fake_read_lock = False
296
201
if not self._lock_held:
297
202
raise LockNotHeld(self)
298
if self._locked_via_token:
299
self._locked_via_token = False
300
self._lock_held = False
302
old_nonce = self.nonce
303
# rename before deleting, because we can't atomically remove the
305
start_time = time.time()
306
self._trace("unlocking")
307
tmpname = '%s/releasing.%s.tmp' % (self.path, rand_chars(20))
308
# gotta own it to unlock
310
self.transport.rename(self._held_dir, tmpname)
311
self._lock_held = False
312
self.transport.delete(tmpname + self.__INFO_NAME)
314
self.transport.rmdir(tmpname)
315
except DirectoryNotEmpty, e:
316
# There might have been junk left over by a rename that moved
317
# another locker within the 'held' directory. do a slower
318
# deletion where we list the directory and remove everything
321
# Maybe this should be broader to allow for ftp servers with
322
# non-specific error messages?
323
self._trace("doing recursive deletion of non-empty directory "
325
self.transport.delete_tree(tmpname)
326
self._trace("... unlock succeeded after %dms",
327
(time.time() - start_time) * 1000)
328
result = lock.LockResult(self.transport.abspath(self.path),
330
for hook in self.hooks['lock_released']:
333
def break_lock(self):
334
"""Break a lock not held by this instance of LockDir.
336
This is a UI centric function: it uses the bzrlib.ui.ui_factory to
337
prompt for input if a lock is detected and there is any doubt about
338
it possibly being still active.
340
self._check_not_locked()
341
holder_info = self.peek()
342
if holder_info is not None:
343
lock_info = '\n'.join(self._format_lock_info(holder_info))
344
if bzrlib.ui.ui_factory.get_boolean("Break %s" % lock_info):
345
self.force_break(holder_info)
203
# rename before deleting, because we can't atomically remove the whole
205
tmpname = '%s.releasing.%s.tmp' % (self.path, rand_chars(20))
206
self.transport.rename(self.path, tmpname)
207
self._lock_held = False
208
self.transport.delete(tmpname + self.__INFO_NAME)
209
self.transport.rmdir(tmpname)
347
211
def force_break(self, dead_holder_info):
348
212
"""Release a lock held by another process.
421
277
Otherwise returns None.
424
info = self._read_info_file(self._held_info_path)
425
self._trace("peek -> held")
280
info = self._read_info_file(self._info_path)
281
assert isinstance(info, dict), \
282
"bad parse result %r" % info
427
284
except NoSuchFile, e:
428
self._trace("peek -> not held")
430
def _prepare_info(self):
287
def _prepare_info(self, outf):
431
288
"""Write information about a pending lock to a temporary file.
433
291
# XXX: is creating this here inefficient?
434
292
config = bzrlib.config.GlobalConfig()
436
user = config.user_email()
437
except errors.NoEmailInUsername:
438
user = config.username()
439
s = rio.Stanza(hostname=get_host_name(),
293
s = Stanza(hostname=socket.gethostname(),
440
294
pid=str(os.getpid()),
441
295
start_time=str(int(time.time())),
442
296
nonce=self.nonce,
297
user=config.user_email(),
299
RioWriter(outf).write_stanza(s)
447
301
def _parse_info(self, info_file):
448
return rio.read_stanza(info_file.readlines()).as_dict()
450
def attempt_lock(self):
451
"""Take the lock; fail if it's already held.
453
If you wish to block until the lock can be obtained, call wait_lock()
456
:return: The lock token.
457
:raises LockContention: if the lock is held by someone else.
459
if self._fake_read_lock:
460
raise LockContention(self)
461
result = self._attempt_lock()
462
hook_result = lock.LockResult(self.transport.abspath(self.path),
464
for hook in self.hooks['lock_acquired']:
468
def wait_lock(self, timeout=None, poll=None, max_attempts=None):
302
return read_stanza(info_file.readlines()).as_dict()
304
def wait_lock(self, timeout=_DEFAULT_TIMEOUT_SECONDS,
305
poll=_DEFAULT_POLL_SECONDS):
469
306
"""Wait a certain period for a lock.
471
308
If the lock can be acquired within the bounded time, it
473
310
is raised. Either way, this function should return within
474
311
approximately `timeout` seconds. (It may be a bit more if
475
312
a transport operation takes a long time to complete.)
477
:param timeout: Approximate maximum amount of time to wait for the
480
:param poll: Delay in seconds between retrying the lock.
482
:param max_attempts: Maximum number of times to try to lock.
484
:return: The lock token.
487
timeout = _DEFAULT_TIMEOUT_SECONDS
489
poll = _DEFAULT_POLL_SECONDS
490
# XXX: the transport interface doesn't let us guard against operations
491
# there taking a long time, so the total elapsed time or poll interval
492
# may be more than was requested.
314
# XXX: the transport interface doesn't let us guard
315
# against operations there taking a long time.
493
316
deadline = time.time() + timeout
500
return self.attempt_lock()
501
321
except LockContention:
502
# possibly report the blockage, then try again
504
# TODO: In a few cases, we find out that there's contention by
505
# reading the held info and observing that it's not ours. In
506
# those cases it's a bit redundant to read it again. However,
507
# the normal case (??) is that the rename fails and so we
508
# don't know who holds the lock. For simplicity we peek
510
new_info = self.peek()
511
if new_info is not None and new_info != last_info:
512
if last_info is None:
513
start = 'Unable to obtain'
515
start = 'Lock owner changed for'
517
formatted_info = self._format_lock_info(new_info)
518
if deadline_str is None:
519
deadline_str = time.strftime('%H:%M:%S',
520
time.localtime(deadline))
521
lock_url = self.transport.abspath(self.path)
522
self._report_function('%s %s\n'
524
'%s\n' # locked ... ago
525
'Will continue to try until %s, unless '
527
'If you\'re sure that it\'s not being '
528
'modified, use bzr break-lock %s',
536
if (max_attempts is not None) and (attempt_count >= max_attempts):
537
self._trace("exceeded %d attempts")
538
raise LockContention(self)
539
323
if time.time() + poll < deadline:
540
self._trace("waiting %ss", poll)
543
self._trace("timeout after waiting %ss", timeout)
544
326
raise LockContention(self)
546
def leave_in_place(self):
547
self._locked_via_token = True
549
def dont_leave_in_place(self):
550
self._locked_via_token = False
552
def lock_write(self, token=None):
553
"""Wait for and acquire the lock.
555
:param token: if this is already locked, then lock_write will fail
556
unless the token matches the existing lock.
557
:returns: a token if this instance supports tokens, otherwise None.
558
:raises TokenLockingNotSupported: when a token is given but this
559
instance doesn't support using token locks.
560
:raises MismatchedToken: if the specified token doesn't match the token
561
of the existing lock.
563
A token should be passed in if you know that you have locked the object
564
some other way, and need to synchronise this object's state with that
567
XXX: docstring duplicated from LockableFiles.lock_write.
569
if token is not None:
570
self.validate_token(token)
572
self._lock_held = True
573
self._locked_via_token = True
576
return self.wait_lock()
328
def lock_write(self):
329
"""Wait for and acquire the lock."""
578
332
def lock_read(self):
579
"""Compatibility-mode shared lock.
333
"""Compatability-mode shared lock.
581
335
LockDir doesn't support shared read-only locks, so this
582
just pretends that the lock is taken but really does nothing.
336
lock is always exclusive.
584
338
# At the moment Branches are commonly locked for read, but
585
339
# we can't rely on that remotely. Once this is cleaned up,
586
340
# reenable this warning to prevent it coming back in
587
341
# -- mbp 20060303
588
342
## warn("LockDir.lock_read falls back to write lock")
589
if self._lock_held or self._fake_read_lock:
590
raise LockContention(self)
591
self._fake_read_lock = True
593
def _format_lock_info(self, info):
594
"""Turn the contents of peek() into something for the user"""
595
lock_url = self.transport.abspath(self.path)
596
delta = time.time() - int(info['start_time'])
598
'lock %s' % (lock_url,),
599
'held by %(user)s on host %(hostname)s [process #%(pid)s]' % info,
600
'locked %s' % (format_delta(delta),),
603
def validate_token(self, token):
604
if token is not None:
610
lock_token = info.get('nonce')
611
if token != lock_token:
612
raise errors.TokenMismatch(token, lock_token)
614
self._trace("revalidated by token %r", token)
616
def _trace(self, format, *args):
617
if 'lock' not in debug.debug_flags:
619
mutter(str(self) + ": " + (format % args))
345
def wait(self, timeout=20, poll=0.5):
346
"""Wait a certain period for a lock to be released."""
347
# XXX: the transport interface doesn't let us guard
348
# against operations there taking a long time.
349
deadline = time.time() + timeout
353
if time.time() + poll < deadline:
356
raise LockContention(self)
added
removed
bzrlib/lockdir.py
