~bzr-pqm/bzr/bzr.dev

1553.5.12 by Martin Pool
New LockDir locking mechanism
1
# Copyright (C) 2006 Canonical Ltd
1887.1.1 by Adeodato Simó
Do not separate paragraphs in the copyright statement with blank lines,
2
#
1553.5.12 by Martin Pool
New LockDir locking mechanism
3
# This program is free software; you can redistribute it and/or modify
4
# it under the terms of the GNU General Public License as published by
5
# the Free Software Foundation; either version 2 of the License, or
6
# (at your option) any later version.
1887.1.1 by Adeodato Simó
Do not separate paragraphs in the copyright statement with blank lines,
7
#
1553.5.12 by Martin Pool
New LockDir locking mechanism
8
# This program is distributed in the hope that it will be useful,
9
# but WITHOUT ANY WARRANTY; without even the implied warranty of
10
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
11
# GNU General Public License for more details.
1887.1.1 by Adeodato Simó
Do not separate paragraphs in the copyright statement with blank lines,
12
#
1553.5.12 by Martin Pool
New LockDir locking mechanism
13
# You should have received a copy of the GNU General Public License
14
# along with this program; if not, write to the Free Software
15
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
16
1553.5.31 by Martin Pool
LockDir doc corrections
17
"""On-disk mutex protecting a resource
1553.5.12 by Martin Pool
New LockDir locking mechanism
18
1553.5.33 by Martin Pool
LockDir review comment fixes
19
bzr on-disk objects are locked by the existence of a directory with a
20
particular name within the control directory.  We use this rather than OS
21
internal locks (such as flock etc) because they can be seen across all
22
transports, including http.
1553.5.12 by Martin Pool
New LockDir locking mechanism
23
24
Objects can be read if there is only physical read access; therefore 
25
readers can never be required to create a lock, though they will
26
check whether a writer is using the lock.  Writers can't detect
27
whether anyone else is reading from the resource as they write.
28
This works because of ordering constraints that make sure readers
29
see a consistent view of existing data.
30
31
Waiting for a lock must be done by polling; this can be aborted after
32
a timeout.
33
34
Locks must always be explicitly released, typically from a try/finally
35
block -- they are not released from a finalizer or when Python
36
exits.
37
38
Locks may fail to be released if the process is abruptly terminated
39
(machine stop, SIGKILL) or if a remote transport becomes permanently
40
disconnected.  There is therefore a method to break an existing lock.
41
This should rarely be used, and generally only with user approval.
42
Locks contain some information on when the lock was taken and by who
43
which may guide in deciding whether it can safely be broken.  (This is
44
similar to the messages displayed by emacs and vim.) Note that if the
45
lock holder is still alive they will get no notification that the lock
46
has been broken and will continue their work -- so it is important to be
47
sure they are actually dead.
48
49
A lock is represented on disk by a directory of a particular name,
50
containing an information file.  Taking a lock is done by renaming a
51
temporary directory into place.  We use temporary directories because
52
for all known transports and filesystems we believe that exactly one
53
attempt to claim the lock will succeed and the others will fail.  (Files
54
won't do because some filesystems or transports only have
55
rename-and-overwrite, making it hard to tell who won.)
56
57
The desired characteristics are:
58
59
* Locks are not reentrant.  (That is, a client that tries to take a 
60
  lock it already holds may deadlock or fail.)
61
* Stale locks can be guessed at by a heuristic
62
* Lost locks can be broken by any client
63
* Failed lock operations leave little or no mess
64
* Deadlocks are avoided by having a timeout always in use, clients
65
  desiring indefinite waits can retry or set a silly big timeout.
66
67
Storage formats use the locks, and also need to consider concurrency
68
issues underneath the lock.  A format may choose not to use a lock
69
at all for some operations.
70
71
LockDirs always operate over a Transport.  The transport may be readonly, in
72
which case the lock can be queried but not acquired.
73
74
Locks are identified by a path name, relative to a base transport.
75
76
Calling code will typically want to make sure there is exactly one LockDir
77
object per actual lock on disk.  This module does nothing to prevent aliasing
78
and deadlocks will likely occur if the locks are aliased.
79
80
In the future we may add a "freshen" method which can be called
81
by a lock holder to check that their lock has not been broken, and to 
82
update the timestamp within it.
83
1553.5.18 by Martin Pool
LockDir should use Transport.rename when releasing locks too.
84
Example usage:
85
86
>>> from bzrlib.transport.memory import MemoryTransport
87
>>> # typically will be obtained from a BzrDir, Branch, etc
88
>>> t = MemoryTransport()
89
>>> l = LockDir(t, 'sample-lock')
1553.5.61 by Martin Pool
Locks protecting LockableFiles must now be explicitly created before use.
90
>>> l.create()
1553.5.18 by Martin Pool
LockDir should use Transport.rename when releasing locks too.
91
>>> l.wait_lock()
92
>>> # do something here
93
>>> l.unlock()
94
1553.5.12 by Martin Pool
New LockDir locking mechanism
95
"""
96
97
import os
98
import time
1957.1.1 by John Arbash Meinel
Report to the user when we are spinning on a lock
99
from cStringIO import StringIO
1553.5.12 by Martin Pool
New LockDir locking mechanism
100
2055.2.1 by John Arbash Meinel
Make LockDir less sensitive to invalid configuration of email
101
from bzrlib import (
102
    errors,
103
    )
1553.5.12 by Martin Pool
New LockDir locking mechanism
104
import bzrlib.config
105
from bzrlib.errors import (
106
        DirectoryNotEmpty,
107
        FileExists,
1553.5.27 by Martin Pool
Confirm that only the intended holder of a lock was broken.
108
        LockBreakMismatch,
1553.5.23 by Martin Pool
Start LockDir.confirm method and LockBroken exception
109
        LockBroken,
1553.5.12 by Martin Pool
New LockDir locking mechanism
110
        LockContention,
111
        LockNotHeld,
112
        NoSuchFile,
1662.1.12 by Martin Pool
Translate unknown sftp errors to PathError, no NoSuchFile
113
        PathError,
1558.10.1 by Aaron Bentley
Handle lockdirs over NFS properly
114
        ResourceBusy,
1553.5.12 by Martin Pool
New LockDir locking mechanism
115
        UnlockableTransport,
116
        )
1957.1.1 by John Arbash Meinel
Report to the user when we are spinning on a lock
117
from bzrlib.trace import mutter, note
1553.5.12 by Martin Pool
New LockDir locking mechanism
118
from bzrlib.transport import Transport
1957.1.5 by John Arbash Meinel
Create a helper function for formatting lock information
119
from bzrlib.osutils import rand_chars, format_delta
1993.1.2 by John Arbash Meinel
Use Stanza.to_string() rather than a RioWriter
120
from bzrlib.rio import read_stanza, Stanza
1553.5.12 by Martin Pool
New LockDir locking mechanism
121
1957.1.15 by John Arbash Meinel
Review feedback from Robert
122
1553.5.12 by Martin Pool
New LockDir locking mechanism
123
# XXX: At the moment there is no consideration of thread safety on LockDir
124
# objects.  This should perhaps be updated - e.g. if two threads try to take a
125
# lock at the same time they should *both* get it.  But then that's unlikely
126
# to be a good idea.
127
128
# TODO: Perhaps store some kind of note like the bzr command line in the lock
129
# info?
130
131
# TODO: Some kind of callback run while polling a lock to show progress
132
# indicators.
133
1553.5.59 by Martin Pool
Pass file/mode bits through to creation of lock files/dirs
134
# TODO: Make sure to pass the right file and directory mode bits to all
135
# files/dirs created.
136
1957.1.15 by John Arbash Meinel
Review feedback from Robert
137
138
_DEFAULT_TIMEOUT_SECONDS = 300
1957.1.9 by John Arbash Meinel
Change default timeouts, and report differently the first failure
139
_DEFAULT_POLL_SECONDS = 1.0
1553.5.12 by Martin Pool
New LockDir locking mechanism
140
1957.1.15 by John Arbash Meinel
Review feedback from Robert
141
1553.5.12 by Martin Pool
New LockDir locking mechanism
142
class LockDir(object):
1553.5.33 by Martin Pool
LockDir review comment fixes
143
    """Write-lock guarding access to data."""
1553.5.12 by Martin Pool
New LockDir locking mechanism
144
1553.5.33 by Martin Pool
LockDir review comment fixes
145
    __INFO_NAME = '/info'
1553.5.12 by Martin Pool
New LockDir locking mechanism
146
1553.5.59 by Martin Pool
Pass file/mode bits through to creation of lock files/dirs
147
    def __init__(self, transport, path, file_modebits=0644, dir_modebits=0755):
1553.5.12 by Martin Pool
New LockDir locking mechanism
148
        """Create a new LockDir object.
149
150
        The LockDir is initially unlocked - this just creates the object.
151
152
        :param transport: Transport which will contain the lock
153
154
        :param path: Path to the lock within the base directory of the 
155
            transport.
156
        """
157
        assert isinstance(transport, Transport), \
158
            ("not a transport: %r" % transport)
159
        self.transport = transport
160
        self.path = path
161
        self._lock_held = False
1553.5.54 by Martin Pool
Add LockDir.read_lock fake method
162
        self._fake_read_lock = False
1553.5.58 by Martin Pool
Change LockDirs to format "lock-name/held/info"
163
        self._held_dir = path + '/held'
164
        self._held_info_path = self._held_dir + self.__INFO_NAME
1553.5.59 by Martin Pool
Pass file/mode bits through to creation of lock files/dirs
165
        self._file_modebits = file_modebits
166
        self._dir_modebits = dir_modebits
1553.5.12 by Martin Pool
New LockDir locking mechanism
167
        self.nonce = rand_chars(20)
168
1957.1.1 by John Arbash Meinel
Report to the user when we are spinning on a lock
169
        self._report_function = note
170
1553.5.12 by Martin Pool
New LockDir locking mechanism
171
    def __repr__(self):
172
        return '%s(%s%s)' % (self.__class__.__name__,
173
                             self.transport.base,
174
                             self.path)
175
1553.5.13 by Martin Pool
New Transport.rename that mustn't overwrite
176
    is_held = property(lambda self: self._lock_held)
1553.5.12 by Martin Pool
New LockDir locking mechanism
177
1666.1.4 by Robert Collins
* 'Metadir' is now the default disk format. This improves behaviour in
178
    def create(self, mode=None):
1553.5.58 by Martin Pool
Change LockDirs to format "lock-name/held/info"
179
        """Create the on-disk lock.
180
181
        This is typically only called when the object/directory containing the 
182
        directory is first created.  The lock is not held when it's created.
183
        """
184
        if self.transport.is_readonly():
185
            raise UnlockableTransport(self.transport)
1666.1.4 by Robert Collins
* 'Metadir' is now the default disk format. This improves behaviour in
186
        self.transport.mkdir(self.path, mode=mode)
1553.5.58 by Martin Pool
Change LockDirs to format "lock-name/held/info"
187
1553.5.12 by Martin Pool
New LockDir locking mechanism
188
    def attempt_lock(self):
1553.5.33 by Martin Pool
LockDir review comment fixes
189
        """Take the lock; fail if it's already held.
1553.5.12 by Martin Pool
New LockDir locking mechanism
190
        
191
        If you wish to block until the lock can be obtained, call wait_lock()
192
        instead.
193
        """
1553.5.54 by Martin Pool
Add LockDir.read_lock fake method
194
        if self._fake_read_lock:
195
            raise LockContention(self)
1553.5.12 by Martin Pool
New LockDir locking mechanism
196
        if self.transport.is_readonly():
197
            raise UnlockableTransport(self.transport)
198
        try:
1553.5.58 by Martin Pool
Change LockDirs to format "lock-name/held/info"
199
            tmpname = '%s/pending.%s.tmp' % (self.path, rand_chars(20))
1955.1.1 by John Arbash Meinel
LockDir can create the root directory if it fails to create a pending directory due to NoSuchFile.
200
            try:
201
                self.transport.mkdir(tmpname)
202
            except NoSuchFile:
203
                # This may raise a FileExists exception
204
                # which is okay, it will be caught later and determined
205
                # to be a LockContention.
206
                self.create(mode=self._dir_modebits)
207
                
208
                # After creating the lock directory, try again
209
                self.transport.mkdir(tmpname)
210
1993.1.2 by John Arbash Meinel
Use Stanza.to_string() rather than a RioWriter
211
            info_bytes = self._prepare_info()
1993.1.1 by John Arbash Meinel
Use put_file_non_atomic in lockdir() to save some sftp round trips
212
            # We use put_file_non_atomic because we just created a new unique
213
            # directory so we don't have to worry about files existing there.
214
            # We'll rename the whole directory into place to get atomic
215
            # properties
1993.1.2 by John Arbash Meinel
Use Stanza.to_string() rather than a RioWriter
216
            self.transport.put_bytes_non_atomic(tmpname + self.__INFO_NAME,
217
                                                info_bytes)
1955.1.1 by John Arbash Meinel
LockDir can create the root directory if it fails to create a pending directory due to NoSuchFile.
218
1553.5.58 by Martin Pool
Change LockDirs to format "lock-name/held/info"
219
            self.transport.rename(tmpname, self._held_dir)
1553.5.12 by Martin Pool
New LockDir locking mechanism
220
            self._lock_held = True
1553.5.33 by Martin Pool
LockDir review comment fixes
221
            self.confirm()
1662.1.12 by Martin Pool
Translate unknown sftp errors to PathError, no NoSuchFile
222
        except (PathError, DirectoryNotEmpty, FileExists, ResourceBusy), e:
223
            mutter("contention on %r: %s", self, e)
224
            raise LockContention(self)
1553.5.12 by Martin Pool
New LockDir locking mechanism
225
226
    def unlock(self):
1553.5.30 by Martin Pool
docstring for LockDir.unlock
227
        """Release a held lock
228
        """
1553.5.54 by Martin Pool
Add LockDir.read_lock fake method
229
        if self._fake_read_lock:
230
            self._fake_read_lock = False
231
            return
1553.5.12 by Martin Pool
New LockDir locking mechanism
232
        if not self._lock_held:
233
            raise LockNotHeld(self)
234
        # rename before deleting, because we can't atomically remove the whole
235
        # tree
1553.5.58 by Martin Pool
Change LockDirs to format "lock-name/held/info"
236
        tmpname = '%s/releasing.%s.tmp' % (self.path, rand_chars(20))
1687.1.3 by Robert Collins
Make LockDir.unlock check the lock is still intact.
237
        # gotta own it to unlock
238
        self.confirm()
1553.5.58 by Martin Pool
Change LockDirs to format "lock-name/held/info"
239
        self.transport.rename(self._held_dir, tmpname)
1553.5.12 by Martin Pool
New LockDir locking mechanism
240
        self._lock_held = False
1553.5.33 by Martin Pool
LockDir review comment fixes
241
        self.transport.delete(tmpname + self.__INFO_NAME)
1553.5.12 by Martin Pool
New LockDir locking mechanism
242
        self.transport.rmdir(tmpname)
243
1687.1.5 by Robert Collins
Add break_lock utility function to LockDir.
244
    def break_lock(self):
245
        """Break a lock not held by this instance of LockDir.
246
247
        This is a UI centric function: it uses the bzrlib.ui.ui_factory to
248
        prompt for input if a lock is detected and there is any doubt about
249
        it possibly being still active.
250
        """
1687.1.6 by Robert Collins
Extend LockableFiles to support break_lock() calls.
251
        self._check_not_locked()
1687.1.5 by Robert Collins
Add break_lock utility function to LockDir.
252
        holder_info = self.peek()
253
        if holder_info is not None:
1957.1.5 by John Arbash Meinel
Create a helper function for formatting lock information
254
            lock_info = '\n'.join(self._format_lock_info(holder_info))
255
            if bzrlib.ui.ui_factory.get_boolean("Break %s" % lock_info):
1687.1.5 by Robert Collins
Add break_lock utility function to LockDir.
256
                self.force_break(holder_info)
257
        
1553.5.27 by Martin Pool
Confirm that only the intended holder of a lock was broken.
258
    def force_break(self, dead_holder_info):
1553.5.25 by Martin Pool
New LockDir.force_break and simple test case
259
        """Release a lock held by another process.
260
261
        WARNING: This should only be used when the other process is dead; if
262
        it still thinks it has the lock there will be two concurrent writers.
263
        In general the user's approval should be sought for lock breaks.
264
1553.5.27 by Martin Pool
Confirm that only the intended holder of a lock was broken.
265
        dead_holder_info must be the result of a previous LockDir.peek() call;
266
        this is used to check that it's still held by the same process that
267
        the user decided was dead.  If this is not the current holder,
268
        LockBreakMismatch is raised.
269
1553.5.25 by Martin Pool
New LockDir.force_break and simple test case
270
        After the lock is broken it will not be held by any process.
271
        It is possible that another process may sneak in and take the 
272
        lock before the breaking process acquires it.
273
        """
1553.5.27 by Martin Pool
Confirm that only the intended holder of a lock was broken.
274
        if not isinstance(dead_holder_info, dict):
275
            raise ValueError("dead_holder_info: %r" % dead_holder_info)
1687.1.6 by Robert Collins
Extend LockableFiles to support break_lock() calls.
276
        self._check_not_locked()
1553.5.27 by Martin Pool
Confirm that only the intended holder of a lock was broken.
277
        current_info = self.peek()
278
        if current_info is None:
1553.5.26 by Martin Pool
Breaking an already-released lock should just succeed
279
            # must have been recently released
280
            return
1553.5.27 by Martin Pool
Confirm that only the intended holder of a lock was broken.
281
        if current_info != dead_holder_info:
282
            raise LockBreakMismatch(self, current_info, dead_holder_info)
1553.5.58 by Martin Pool
Change LockDirs to format "lock-name/held/info"
283
        tmpname = '%s/broken.%s.tmp' % (self.path, rand_chars(20))
284
        self.transport.rename(self._held_dir, tmpname)
1553.5.27 by Martin Pool
Confirm that only the intended holder of a lock was broken.
285
        # check that we actually broke the right lock, not someone else;
286
        # there's a small race window between checking it and doing the 
287
        # rename.
1553.5.33 by Martin Pool
LockDir review comment fixes
288
        broken_info_path = tmpname + self.__INFO_NAME
289
        broken_info = self._read_info_file(broken_info_path)
1553.5.27 by Martin Pool
Confirm that only the intended holder of a lock was broken.
290
        if broken_info != dead_holder_info:
291
            raise LockBreakMismatch(self, broken_info, dead_holder_info)
292
        self.transport.delete(broken_info_path)
1553.5.25 by Martin Pool
New LockDir.force_break and simple test case
293
        self.transport.rmdir(tmpname)
294
1687.1.6 by Robert Collins
Extend LockableFiles to support break_lock() calls.
295
    def _check_not_locked(self):
296
        """If the lock is held by this instance, raise an error."""
297
        if self._lock_held:
298
            raise AssertionError("can't break own lock: %r" % self)
299
1553.5.20 by Martin Pool
Start adding LockDir.confirm() method
300
    def confirm(self):
301
        """Make sure that the lock is still held by this locker.
302
303
        This should only fail if the lock was broken by user intervention,
304
        or if the lock has been affected by a bug.
305
306
        If the lock is not thought to be held, raises LockNotHeld.  If
307
        the lock is thought to be held but has been broken, raises 
308
        LockBroken.
309
        """
310
        if not self._lock_held:
311
            raise LockNotHeld(self)
1553.5.23 by Martin Pool
Start LockDir.confirm method and LockBroken exception
312
        info = self.peek()
313
        if info is None:
314
            # no lock there anymore!
315
            raise LockBroken(self)
316
        if info.get('nonce') != self.nonce:
317
            # there is a lock, but not ours
318
            raise LockBroken(self)
1553.5.33 by Martin Pool
LockDir review comment fixes
319
        
320
    def _read_info_file(self, path):
1553.5.58 by Martin Pool
Change LockDirs to format "lock-name/held/info"
321
        """Read one given info file.
322
323
        peek() reads the info file of the lock holder, if any.
324
        """
1553.5.33 by Martin Pool
LockDir review comment fixes
325
        return self._parse_info(self.transport.get(path))
1553.5.20 by Martin Pool
Start adding LockDir.confirm() method
326
1553.5.12 by Martin Pool
New LockDir locking mechanism
327
    def peek(self):
328
        """Check if the lock is held by anyone.
329
        
330
        If it is held, this returns the lock info structure as a rio Stanza,
331
        which contains some information about the current lock holder.
332
        Otherwise returns None.
333
        """
334
        try:
1553.5.58 by Martin Pool
Change LockDirs to format "lock-name/held/info"
335
            info = self._read_info_file(self._held_info_path)
1553.5.27 by Martin Pool
Confirm that only the intended holder of a lock was broken.
336
            assert isinstance(info, dict), \
1553.5.12 by Martin Pool
New LockDir locking mechanism
337
                    "bad parse result %r" % info
1553.5.27 by Martin Pool
Confirm that only the intended holder of a lock was broken.
338
            return info
1553.5.12 by Martin Pool
New LockDir locking mechanism
339
        except NoSuchFile, e:
340
            return None
341
1993.1.2 by John Arbash Meinel
Use Stanza.to_string() rather than a RioWriter
342
    def _prepare_info(self):
1553.5.12 by Martin Pool
New LockDir locking mechanism
343
        """Write information about a pending lock to a temporary file.
344
        """
345
        import socket
346
        # XXX: is creating this here inefficient?
347
        config = bzrlib.config.GlobalConfig()
2055.2.1 by John Arbash Meinel
Make LockDir less sensitive to invalid configuration of email
348
        try:
349
            user = config.user_email()
2055.2.2 by John Arbash Meinel
Switch extract_email_address() to use a more specific exception
350
        except errors.NoEmailInUsername:
2055.2.1 by John Arbash Meinel
Make LockDir less sensitive to invalid configuration of email
351
            user = config.username()
1553.5.12 by Martin Pool
New LockDir locking mechanism
352
        s = Stanza(hostname=socket.gethostname(),
353
                   pid=str(os.getpid()),
354
                   start_time=str(int(time.time())),
355
                   nonce=self.nonce,
2055.2.1 by John Arbash Meinel
Make LockDir less sensitive to invalid configuration of email
356
                   user=user,
1553.5.12 by Martin Pool
New LockDir locking mechanism
357
                   )
1993.1.2 by John Arbash Meinel
Use Stanza.to_string() rather than a RioWriter
358
        return s.to_string()
1553.5.12 by Martin Pool
New LockDir locking mechanism
359
360
    def _parse_info(self, info_file):
1553.5.27 by Martin Pool
Confirm that only the intended holder of a lock was broken.
361
        return read_stanza(info_file.readlines()).as_dict()
1553.5.12 by Martin Pool
New LockDir locking mechanism
362
1957.1.17 by John Arbash Meinel
Change tests that expect locking to fail to timeout sooner.
363
    def wait_lock(self, timeout=None, poll=None):
1553.5.12 by Martin Pool
New LockDir locking mechanism
364
        """Wait a certain period for a lock.
365
366
        If the lock can be acquired within the bounded time, it
367
        is taken and this returns.  Otherwise, LockContention
368
        is raised.  Either way, this function should return within
369
        approximately `timeout` seconds.  (It may be a bit more if
370
        a transport operation takes a long time to complete.)
371
        """
1957.1.17 by John Arbash Meinel
Change tests that expect locking to fail to timeout sooner.
372
        if timeout is None:
373
            timeout = _DEFAULT_TIMEOUT_SECONDS
374
        if poll is None:
375
            poll = _DEFAULT_POLL_SECONDS
376
1553.5.12 by Martin Pool
New LockDir locking mechanism
377
        # XXX: the transport interface doesn't let us guard 
378
        # against operations there taking a long time.
379
        deadline = time.time() + timeout
1957.1.13 by John Arbash Meinel
Change to reporting the time when we will stop trying to grab the lock
380
        deadline_str = None
1957.1.7 by John Arbash Meinel
Add the ability to report if the lock changes from underneath you
381
        last_info = None
1553.5.12 by Martin Pool
New LockDir locking mechanism
382
        while True:
383
            try:
384
                self.attempt_lock()
385
                return
386
            except LockContention:
387
                pass
1957.1.7 by John Arbash Meinel
Add the ability to report if the lock changes from underneath you
388
            new_info = self.peek()
389
            mutter('last_info: %s, new info: %s', last_info, new_info)
390
            if new_info is not None and new_info != last_info:
1957.1.9 by John Arbash Meinel
Change default timeouts, and report differently the first failure
391
                if last_info is None:
392
                    start = 'Unable to obtain'
393
                else:
394
                    start = 'Lock owner changed for'
1957.1.7 by John Arbash Meinel
Add the ability to report if the lock changes from underneath you
395
                last_info = new_info
396
                formatted_info = self._format_lock_info(new_info)
1957.1.13 by John Arbash Meinel
Change to reporting the time when we will stop trying to grab the lock
397
                if deadline_str is None:
398
                    deadline_str = time.strftime('%H:%M:%S',
399
                                                 time.localtime(deadline))
1957.1.9 by John Arbash Meinel
Change default timeouts, and report differently the first failure
400
                self._report_function('%s %s\n'
1957.1.7 by John Arbash Meinel
Add the ability to report if the lock changes from underneath you
401
                                      '%s\n' # held by
402
                                      '%s\n' # locked ... ago
1957.1.13 by John Arbash Meinel
Change to reporting the time when we will stop trying to grab the lock
403
                                      'Will continue to try until %s\n',
1957.1.9 by John Arbash Meinel
Change default timeouts, and report differently the first failure
404
                                      start,
1957.1.7 by John Arbash Meinel
Add the ability to report if the lock changes from underneath you
405
                                      formatted_info[0],
406
                                      formatted_info[1],
407
                                      formatted_info[2],
1957.1.13 by John Arbash Meinel
Change to reporting the time when we will stop trying to grab the lock
408
                                      deadline_str)
1957.1.1 by John Arbash Meinel
Report to the user when we are spinning on a lock
409
1553.5.12 by Martin Pool
New LockDir locking mechanism
410
            if time.time() + poll < deadline:
411
                time.sleep(poll)
412
            else:
413
                raise LockContention(self)
414
1553.5.44 by Martin Pool
LockableFiles can now call LockDir directly
415
    def lock_write(self):
416
        """Wait for and acquire the lock."""
1957.1.2 by John Arbash Meinel
Switch the default from instantly aborting, to waiting as long as 1 minute (down from 5 minutes)
417
        self.wait_lock()
1553.5.44 by Martin Pool
LockableFiles can now call LockDir directly
418
419
    def lock_read(self):
1759.2.1 by Jelmer Vernooij
Fix some types (found using aspell).
420
        """Compatibility-mode shared lock.
1553.5.44 by Martin Pool
LockableFiles can now call LockDir directly
421
422
        LockDir doesn't support shared read-only locks, so this 
1553.5.54 by Martin Pool
Add LockDir.read_lock fake method
423
        just pretends that the lock is taken but really does nothing.
1553.5.44 by Martin Pool
LockableFiles can now call LockDir directly
424
        """
425
        # At the moment Branches are commonly locked for read, but 
426
        # we can't rely on that remotely.  Once this is cleaned up,
427
        # reenable this warning to prevent it coming back in 
428
        # -- mbp 20060303
429
        ## warn("LockDir.lock_read falls back to write lock")
1553.5.54 by Martin Pool
Add LockDir.read_lock fake method
430
        if self._lock_held or self._fake_read_lock:
431
            raise LockContention(self)
432
        self._fake_read_lock = True
1553.5.44 by Martin Pool
LockableFiles can now call LockDir directly
433
1553.5.12 by Martin Pool
New LockDir locking mechanism
434
    def wait(self, timeout=20, poll=0.5):
1553.5.33 by Martin Pool
LockDir review comment fixes
435
        """Wait a certain period for a lock to be released."""
1553.5.12 by Martin Pool
New LockDir locking mechanism
436
        # XXX: the transport interface doesn't let us guard 
437
        # against operations there taking a long time.
438
        deadline = time.time() + timeout
439
        while True:
440
            if self.peek():
441
                return
442
            if time.time() + poll < deadline:
443
                time.sleep(poll)
444
            else:
445
                raise LockContention(self)
1553.5.25 by Martin Pool
New LockDir.force_break and simple test case
446
1957.1.5 by John Arbash Meinel
Create a helper function for formatting lock information
447
    def _format_lock_info(self, info):
448
        """Turn the contents of peek() into something for the user"""
449
        lock_url = self.transport.abspath(self.path)
450
        delta = time.time() - int(info['start_time'])
451
        return [
452
            'lock %s' % (lock_url,),
453
            'held by %(user)s on host %(hostname)s [process #%(pid)s]' % info,
454
            'locked %s' % (format_delta(delta),),
455
            ]
456