~bzr-pqm/bzr/bzr.dev

3331.3.5 by Martin Pool
Move physical lock hooks onto new PhysicalLock class variable
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# Copyright (C) 2006, 2007, 2008 Canonical Ltd
1887.1.1 by Adeodato Simó
Do not separate paragraphs in the copyright statement with blank lines,
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#
1553.5.12 by Martin Pool
New LockDir locking mechanism
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
1887.1.1 by Adeodato Simó
Do not separate paragraphs in the copyright statement with blank lines,
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#
1553.5.12 by Martin Pool
New LockDir locking mechanism
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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# GNU General Public License for more details.
1887.1.1 by Adeodato Simó
Do not separate paragraphs in the copyright statement with blank lines,
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#
1553.5.12 by Martin Pool
New LockDir locking mechanism
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
4183.7.1 by Sabin Iacob
update FSF mailing address
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
1553.5.12 by Martin Pool
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1553.5.31 by Martin Pool
LockDir doc corrections
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"""On-disk mutex protecting a resource
1553.5.12 by Martin Pool
New LockDir locking mechanism
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1553.5.33 by Martin Pool
LockDir review comment fixes
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bzr on-disk objects are locked by the existence of a directory with a
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particular name within the control directory.  We use this rather than OS
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internal locks (such as flock etc) because they can be seen across all
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transports, including http.
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3943.8.1 by Marius Kruger
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Objects can be read if there is only physical read access; therefore
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New LockDir locking mechanism
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readers can never be required to create a lock, though they will
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check whether a writer is using the lock.  Writers can't detect
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whether anyone else is reading from the resource as they write.
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This works because of ordering constraints that make sure readers
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see a consistent view of existing data.
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Waiting for a lock must be done by polling; this can be aborted after
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a timeout.
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Locks must always be explicitly released, typically from a try/finally
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block -- they are not released from a finalizer or when Python
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exits.
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Locks may fail to be released if the process is abruptly terminated
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(machine stop, SIGKILL) or if a remote transport becomes permanently
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disconnected.  There is therefore a method to break an existing lock.
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This should rarely be used, and generally only with user approval.
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Locks contain some information on when the lock was taken and by who
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which may guide in deciding whether it can safely be broken.  (This is
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similar to the messages displayed by emacs and vim.) Note that if the
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lock holder is still alive they will get no notification that the lock
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has been broken and will continue their work -- so it is important to be
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sure they are actually dead.
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A lock is represented on disk by a directory of a particular name,
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containing an information file.  Taking a lock is done by renaming a
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temporary directory into place.  We use temporary directories because
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for all known transports and filesystems we believe that exactly one
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attempt to claim the lock will succeed and the others will fail.  (Files
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won't do because some filesystems or transports only have
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rename-and-overwrite, making it hard to tell who won.)
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The desired characteristics are:
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3943.8.1 by Marius Kruger
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* Locks are not reentrant.  (That is, a client that tries to take a
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  lock it already holds may deadlock or fail.)
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* Stale locks can be guessed at by a heuristic
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* Lost locks can be broken by any client
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* Failed lock operations leave little or no mess
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* Deadlocks are avoided by having a timeout always in use, clients
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  desiring indefinite waits can retry or set a silly big timeout.
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Storage formats use the locks, and also need to consider concurrency
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issues underneath the lock.  A format may choose not to use a lock
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at all for some operations.
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LockDirs always operate over a Transport.  The transport may be readonly, in
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which case the lock can be queried but not acquired.
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Locks are identified by a path name, relative to a base transport.
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Calling code will typically want to make sure there is exactly one LockDir
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object per actual lock on disk.  This module does nothing to prevent aliasing
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and deadlocks will likely occur if the locks are aliased.
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In the future we may add a "freshen" method which can be called
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by a lock holder to check that their lock has not been broken, and to
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update the timestamp within it.
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1553.5.18 by Martin Pool
LockDir should use Transport.rename when releasing locks too.
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Example usage:
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>>> from bzrlib.transport.memory import MemoryTransport
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>>> # typically will be obtained from a BzrDir, Branch, etc
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>>> t = MemoryTransport()
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>>> l = LockDir(t, 'sample-lock')
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Locks protecting LockableFiles must now be explicitly created before use.
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>>> l.create()
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fix up doctest example for token being returned from wait_lock
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>>> token = l.wait_lock()
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>>> # do something here
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>>> l.unlock()
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"""
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2555.3.10 by Martin Pool
doc
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# TODO: We sometimes have the problem that our attempt to rename '1234' to
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# 'held' fails because the transport server moves into an existing directory,
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# rather than failing the rename.  If we made the info file name the same as
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# the locked directory name we would avoid this problem because moving into
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# the held directory would implicitly clash.  However this would not mesh with
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# the existing locking code and needs a new format of the containing object.
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# -- robertc, mbp 20070628
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import os
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import time
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2055.2.1 by John Arbash Meinel
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from bzrlib import (
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    debug,
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    errors,
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* ``LockDir`` lock acquisition and release now trigger hooks allowing
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    lock,
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    )
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import bzrlib.config
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from bzrlib.errors import (
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        DirectoryNotEmpty,
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        FileExists,
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Confirm that only the intended holder of a lock was broken.
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        LockBreakMismatch,
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Start LockDir.confirm method and LockBroken exception
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        LockBroken,
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        LockContention,
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        LockFailed,
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        LockNotHeld,
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        NoSuchFile,
1662.1.12 by Martin Pool
Translate unknown sftp errors to PathError, no NoSuchFile
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        PathError,
1558.10.1 by Aaron Bentley
Handle lockdirs over NFS properly
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        ResourceBusy,
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        TransportError,
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        )
1957.1.1 by John Arbash Meinel
Report to the user when we are spinning on a lock
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from bzrlib.trace import mutter, note
3224.5.40 by Andrew Bennetts
Keep importing format_delta into lockdir.py (why does pyflakes say it is unused?)
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from bzrlib.osutils import format_delta, rand_chars, get_host_name
3224.5.31 by Andrew Bennetts
A couple more lazy imports, helps 'bzr log --line -r -1' a little.
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import bzrlib.ui
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from bzrlib.lazy_import import lazy_import
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lazy_import(globals(), """
3224.5.39 by Andrew Bennetts
Tweak lazy_import in lockdir.py to avoid confusing DocTestSuite
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from bzrlib import rio
3224.5.31 by Andrew Bennetts
A couple more lazy imports, helps 'bzr log --line -r -1' a little.
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""")
1957.1.15 by John Arbash Meinel
Review feedback from Robert
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# XXX: At the moment there is no consideration of thread safety on LockDir
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# objects.  This should perhaps be updated - e.g. if two threads try to take a
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# lock at the same time they should *both* get it.  But then that's unlikely
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# to be a good idea.
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# TODO: Perhaps store some kind of note like the bzr command line in the lock
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# info?
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# TODO: Some kind of callback run while polling a lock to show progress
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# indicators.
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1553.5.59 by Martin Pool
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# TODO: Make sure to pass the right file and directory mode bits to all
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# files/dirs created.
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1957.1.15 by John Arbash Meinel
Review feedback from Robert
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_DEFAULT_TIMEOUT_SECONDS = 300
1957.1.9 by John Arbash Meinel
Change default timeouts, and report differently the first failure
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_DEFAULT_POLL_SECONDS = 1.0
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1957.1.15 by John Arbash Meinel
Review feedback from Robert
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3724.1.1 by Martin Pool
Move Lock hooks onto a base Lock class and make them more consistent with other lock classes
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class LockDir(lock.Lock):
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    """Write-lock guarding access to data.
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    """
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LockDir review comment fixes
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    __INFO_NAME = '/info'
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    def __init__(self, transport, path, file_modebits=0644, dir_modebits=0755):
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        """Create a new LockDir object.
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        The LockDir is initially unlocked - this just creates the object.
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        :param transport: Transport which will contain the lock
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3943.8.1 by Marius Kruger
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        :param path: Path to the lock within the base directory of the
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            transport.
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        """
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        self.transport = transport
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        self.path = path
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        self._lock_held = False
2279.7.1 by Andrew Bennetts
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        self._locked_via_token = False
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        self._fake_read_lock = False
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        self._held_dir = path + '/held'
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        self._held_info_path = self._held_dir + self.__INFO_NAME
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        self._file_modebits = file_modebits
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        self._dir_modebits = dir_modebits
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        self._report_function = note
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    def __repr__(self):
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        return '%s(%s%s)' % (self.__class__.__name__,
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                             self.transport.base,
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                             self.path)
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1553.5.13 by Martin Pool
New Transport.rename that mustn't overwrite
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    is_held = property(lambda self: self._lock_held)
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1666.1.4 by Robert Collins
* 'Metadir' is now the default disk format. This improves behaviour in
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    def create(self, mode=None):
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        """Create the on-disk lock.
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        This is typically only called when the object/directory containing the
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        directory is first created.  The lock is not held when it's created.
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        """
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        self._trace("create lock directory")
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        try:
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            self.transport.mkdir(self.path, mode=mode)
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        except (TransportError, PathError), e:
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            raise LockFailed(self, e)
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1553.5.58 by Martin Pool
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2555.3.20 by Martin Pool
rename _lock_core to _attempt_lock
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    def _attempt_lock(self):
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        """Make the pending directory and attempt to rename into place.
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        If the rename succeeds, we read back the info file to check that we
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        really got the lock.
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        If we fail to acquire the lock, this method is responsible for
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        cleaning up the pending directory if possible.  (But it doesn't do
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        that yet.)
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        :returns: The nonce of the lock, if it was successfully acquired.
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        :raises LockContention: If the lock is held by someone else.  The exception
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            contains the info of the current holder of the lock.
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        """
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        self._trace("lock_write...")
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        start_time = time.time()
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        try:
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            tmpname = self._create_pending_dir()
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        except (errors.TransportError, PathError), e:
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            self._trace("... failed to create pending dir, %s", e)
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            raise LockFailed(self, e)
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        try:
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            self.transport.rename(tmpname, self._held_dir)
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        except (errors.TransportError, PathError, DirectoryNotEmpty,
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                FileExists, ResourceBusy), e:
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            self._trace("... contention, %s", e)
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            self._remove_pending_dir(tmpname)
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            raise LockContention(self)
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        except Exception, e:
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            self._trace("... lock failed, %s", e)
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            self._remove_pending_dir(tmpname)
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            raise
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        # We must check we really got the lock, because Launchpad's sftp
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        # server at one time had a bug were the rename would successfully
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        # move the new directory into the existing directory, which was
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        # incorrect.  It's possible some other servers or filesystems will
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        # have a similar bug allowing someone to think they got the lock
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        # when it's already held.
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        info = self.peek()
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        self._trace("after locking, info=%r", info)
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        if info['nonce'] != self.nonce:
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            self._trace("rename succeeded, "
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                "but lock is still held by someone else")
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            raise LockContention(self)
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        self._lock_held = True
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        self._trace("... lock succeeded after %dms",
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                (time.time() - start_time) * 1000)
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Restore disabled LockDir trace message
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        return self.nonce
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2555.3.16 by Martin Pool
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    def _remove_pending_dir(self, tmpname):
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        """Remove the pending directory
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        This is called if we failed to rename into place, so that the pending
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Clean up patch to make divergence from mainline smaller.
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        dirs don't clutter up the lockdir.
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        """
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        self._trace("remove %s", tmpname)
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Don't fail hard when removing pending lockdir
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        try:
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            self.transport.delete(tmpname + self.__INFO_NAME)
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            self.transport.rmdir(tmpname)
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        except PathError, e:
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            note("error removing pending lock: %s", e)
2555.3.16 by Martin Pool
Clean up patch to make divergence from mainline smaller.
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2555.3.13 by Martin Pool
LockDir cleanups
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    def _create_pending_dir(self):
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        tmpname = '%s/%s.tmp' % (self.path, rand_chars(10))
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        try:
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            self.transport.mkdir(tmpname)
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        except NoSuchFile:
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            # This may raise a FileExists exception
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            # which is okay, it will be caught later and determined
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            # to be a LockContention.
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            self._trace("lock directory does not exist, creating it")
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            self.create(mode=self._dir_modebits)
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            # After creating the lock directory, try again
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            self.transport.mkdir(tmpname)
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        self.nonce = rand_chars(20)
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        info_bytes = self._prepare_info()
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        # We use put_file_non_atomic because we just created a new unique
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        # directory so we don't have to worry about files existing there.
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        # We'll rename the whole directory into place to get atomic
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        # properties
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        self.transport.put_bytes_non_atomic(tmpname + self.__INFO_NAME,
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                                            info_bytes)
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        return tmpname
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    def unlock(self):
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docstring for LockDir.unlock
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        """Release a held lock
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        """
1553.5.54 by Martin Pool
Add LockDir.read_lock fake method
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        if self._fake_read_lock:
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            self._fake_read_lock = False
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            return
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        if not self._lock_held:
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            raise LockNotHeld(self)
2279.7.1 by Andrew Bennetts
``LockableFiles.lock_write()`` now accepts a ``token`` keyword argument, so that
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        if self._locked_via_token:
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            self._locked_via_token = False
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            self._lock_held = False
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        else:
3331.3.1 by Robert Collins
* ``LockDir`` lock acquisition and release now trigger hooks allowing
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            old_nonce = self.nonce
2279.7.1 by Andrew Bennetts
``LockableFiles.lock_write()`` now accepts a ``token`` keyword argument, so that
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            # rename before deleting, because we can't atomically remove the
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            # whole tree
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            start_time = time.time()
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            self._trace("unlocking")
2279.7.1 by Andrew Bennetts
``LockableFiles.lock_write()`` now accepts a ``token`` keyword argument, so that
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            tmpname = '%s/releasing.%s.tmp' % (self.path, rand_chars(20))
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            # gotta own it to unlock
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            self.confirm()
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            self.transport.rename(self._held_dir, tmpname)
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            self._lock_held = False
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            self.transport.delete(tmpname + self.__INFO_NAME)
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Better handling in LockDir of rename that moves one directory within another
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            try:
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                self.transport.rmdir(tmpname)
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            except DirectoryNotEmpty, e:
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                # There might have been junk left over by a rename that moved
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                # another locker within the 'held' directory.  do a slower
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                # deletion where we list the directory and remove everything
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                # within it.
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                #
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                # Maybe this should be broader to allow for ftp servers with
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                # non-specific error messages?
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                self._trace("doing recursive deletion of non-empty directory "
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                        "%s", tmpname)
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                self.transport.delete_tree(tmpname)
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Simple lock tracing in LockDir
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            self._trace("... unlock succeeded after %dms",
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                    (time.time() - start_time) * 1000)
3331.3.2 by Robert Collins
Polish on lock hooks to be easier to use.
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            result = lock.LockResult(self.transport.abspath(self.path),
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                old_nonce)
3331.3.6 by Martin Pool
merge trunk
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            for hook in self.hooks['lock_released']:
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* ``LockDir`` lock acquisition and release now trigger hooks allowing
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                hook(result)
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New LockDir locking mechanism
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1687.1.5 by Robert Collins
Add break_lock utility function to LockDir.
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    def break_lock(self):
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        """Break a lock not held by this instance of LockDir.
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        This is a UI centric function: it uses the bzrlib.ui.ui_factory to
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        prompt for input if a lock is detected and there is any doubt about
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        it possibly being still active.
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        """
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Extend LockableFiles to support break_lock() calls.
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        self._check_not_locked()
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Add break_lock utility function to LockDir.
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        holder_info = self.peek()
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        if holder_info is not None:
1957.1.5 by John Arbash Meinel
Create a helper function for formatting lock information
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            lock_info = '\n'.join(self._format_lock_info(holder_info))
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            if bzrlib.ui.ui_factory.get_boolean("Break %s" % lock_info):
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Add break_lock utility function to LockDir.
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                self.force_break(holder_info)
3943.8.1 by Marius Kruger
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1553.5.27 by Martin Pool
Confirm that only the intended holder of a lock was broken.
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    def force_break(self, dead_holder_info):
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New LockDir.force_break and simple test case
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        """Release a lock held by another process.
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        WARNING: This should only be used when the other process is dead; if
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        it still thinks it has the lock there will be two concurrent writers.
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        In general the user's approval should be sought for lock breaks.
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Confirm that only the intended holder of a lock was broken.
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        dead_holder_info must be the result of a previous LockDir.peek() call;
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        this is used to check that it's still held by the same process that
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        the user decided was dead.  If this is not the current holder,
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        LockBreakMismatch is raised.
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New LockDir.force_break and simple test case
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        After the lock is broken it will not be held by any process.
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        It is possible that another process may sneak in and take the
1553.5.25 by Martin Pool
New LockDir.force_break and simple test case
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        lock before the breaking process acquires it.
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        """
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Confirm that only the intended holder of a lock was broken.
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        if not isinstance(dead_holder_info, dict):
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            raise ValueError("dead_holder_info: %r" % dead_holder_info)
1687.1.6 by Robert Collins
Extend LockableFiles to support break_lock() calls.
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        self._check_not_locked()
1553.5.27 by Martin Pool
Confirm that only the intended holder of a lock was broken.
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        current_info = self.peek()
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        if current_info is None:
1553.5.26 by Martin Pool
Breaking an already-released lock should just succeed
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            # must have been recently released
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            return
1553.5.27 by Martin Pool
Confirm that only the intended holder of a lock was broken.
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        if current_info != dead_holder_info:
370
            raise LockBreakMismatch(self, current_info, dead_holder_info)
1553.5.58 by Martin Pool
Change LockDirs to format "lock-name/held/info"
371
        tmpname = '%s/broken.%s.tmp' % (self.path, rand_chars(20))
372
        self.transport.rename(self._held_dir, tmpname)
1553.5.27 by Martin Pool
Confirm that only the intended holder of a lock was broken.
373
        # check that we actually broke the right lock, not someone else;
3943.8.1 by Marius Kruger
remove all trailing whitespace from bzr source
374
        # there's a small race window between checking it and doing the
1553.5.27 by Martin Pool
Confirm that only the intended holder of a lock was broken.
375
        # rename.
1553.5.33 by Martin Pool
LockDir review comment fixes
376
        broken_info_path = tmpname + self.__INFO_NAME
377
        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.
378
        if broken_info != dead_holder_info:
379
            raise LockBreakMismatch(self, broken_info, dead_holder_info)
380
        self.transport.delete(broken_info_path)
1553.5.25 by Martin Pool
New LockDir.force_break and simple test case
381
        self.transport.rmdir(tmpname)
382
1687.1.6 by Robert Collins
Extend LockableFiles to support break_lock() calls.
383
    def _check_not_locked(self):
384
        """If the lock is held by this instance, raise an error."""
385
        if self._lock_held:
386
            raise AssertionError("can't break own lock: %r" % self)
387
1553.5.20 by Martin Pool
Start adding LockDir.confirm() method
388
    def confirm(self):
389
        """Make sure that the lock is still held by this locker.
390
391
        This should only fail if the lock was broken by user intervention,
392
        or if the lock has been affected by a bug.
393
394
        If the lock is not thought to be held, raises LockNotHeld.  If
3943.8.1 by Marius Kruger
remove all trailing whitespace from bzr source
395
        the lock is thought to be held but has been broken, raises
1553.5.20 by Martin Pool
Start adding LockDir.confirm() method
396
        LockBroken.
397
        """
398
        if not self._lock_held:
399
            raise LockNotHeld(self)
1553.5.23 by Martin Pool
Start LockDir.confirm method and LockBroken exception
400
        info = self.peek()
401
        if info is None:
402
            # no lock there anymore!
403
            raise LockBroken(self)
404
        if info.get('nonce') != self.nonce:
405
            # there is a lock, but not ours
406
            raise LockBroken(self)
3943.8.1 by Marius Kruger
remove all trailing whitespace from bzr source
407
1553.5.33 by Martin Pool
LockDir review comment fixes
408
    def _read_info_file(self, path):
1553.5.58 by Martin Pool
Change LockDirs to format "lock-name/held/info"
409
        """Read one given info file.
410
411
        peek() reads the info file of the lock holder, if any.
412
        """
1553.5.33 by Martin Pool
LockDir review comment fixes
413
        return self._parse_info(self.transport.get(path))
1553.5.20 by Martin Pool
Start adding LockDir.confirm() method
414
1553.5.12 by Martin Pool
New LockDir locking mechanism
415
    def peek(self):
416
        """Check if the lock is held by anyone.
3943.8.1 by Marius Kruger
remove all trailing whitespace from bzr source
417
1553.5.12 by Martin Pool
New LockDir locking mechanism
418
        If it is held, this returns the lock info structure as a rio Stanza,
419
        which contains some information about the current lock holder.
420
        Otherwise returns None.
421
        """
422
        try:
1553.5.58 by Martin Pool
Change LockDirs to format "lock-name/held/info"
423
            info = self._read_info_file(self._held_info_path)
2555.3.3 by Martin Pool
Simple lock tracing in LockDir
424
            self._trace("peek -> held")
1553.5.27 by Martin Pool
Confirm that only the intended holder of a lock was broken.
425
            return info
1553.5.12 by Martin Pool
New LockDir locking mechanism
426
        except NoSuchFile, e:
2555.3.3 by Martin Pool
Simple lock tracing in LockDir
427
            self._trace("peek -> not held")
1553.5.12 by Martin Pool
New LockDir locking mechanism
428
1993.1.2 by John Arbash Meinel
Use Stanza.to_string() rather than a RioWriter
429
    def _prepare_info(self):
1553.5.12 by Martin Pool
New LockDir locking mechanism
430
        """Write information about a pending lock to a temporary file.
431
        """
432
        # XXX: is creating this here inefficient?
433
        config = bzrlib.config.GlobalConfig()
2055.2.1 by John Arbash Meinel
Make LockDir less sensitive to invalid configuration of email
434
        try:
435
            user = config.user_email()
2055.2.2 by John Arbash Meinel
Switch extract_email_address() to use a more specific exception
436
        except errors.NoEmailInUsername:
2055.2.1 by John Arbash Meinel
Make LockDir less sensitive to invalid configuration of email
437
            user = config.username()
3224.5.39 by Andrew Bennetts
Tweak lazy_import in lockdir.py to avoid confusing DocTestSuite
438
        s = rio.Stanza(hostname=get_host_name(),
1553.5.12 by Martin Pool
New LockDir locking mechanism
439
                   pid=str(os.getpid()),
440
                   start_time=str(int(time.time())),
441
                   nonce=self.nonce,
2055.2.1 by John Arbash Meinel
Make LockDir less sensitive to invalid configuration of email
442
                   user=user,
1553.5.12 by Martin Pool
New LockDir locking mechanism
443
                   )
1993.1.2 by John Arbash Meinel
Use Stanza.to_string() rather than a RioWriter
444
        return s.to_string()
1553.5.12 by Martin Pool
New LockDir locking mechanism
445
446
    def _parse_info(self, info_file):
3224.5.39 by Andrew Bennetts
Tweak lazy_import in lockdir.py to avoid confusing DocTestSuite
447
        return rio.read_stanza(info_file.readlines()).as_dict()
1553.5.12 by Martin Pool
New LockDir locking mechanism
448
2555.3.13 by Martin Pool
LockDir cleanups
449
    def attempt_lock(self):
450
        """Take the lock; fail if it's already held.
3943.8.1 by Marius Kruger
remove all trailing whitespace from bzr source
451
2555.3.13 by Martin Pool
LockDir cleanups
452
        If you wish to block until the lock can be obtained, call wait_lock()
453
        instead.
454
455
        :return: The lock token.
456
        :raises LockContention: if the lock is held by someone else.
457
        """
2555.3.16 by Martin Pool
Clean up patch to make divergence from mainline smaller.
458
        if self._fake_read_lock:
459
            raise LockContention(self)
3331.3.1 by Robert Collins
* ``LockDir`` lock acquisition and release now trigger hooks allowing
460
        result = self._attempt_lock()
3331.3.2 by Robert Collins
Polish on lock hooks to be easier to use.
461
        hook_result = lock.LockResult(self.transport.abspath(self.path),
462
                self.nonce)
3331.3.6 by Martin Pool
merge trunk
463
        for hook in self.hooks['lock_acquired']:
3331.3.1 by Robert Collins
* ``LockDir`` lock acquisition and release now trigger hooks allowing
464
            hook(hook_result)
465
        return result
2555.3.13 by Martin Pool
LockDir cleanups
466
467
    def wait_lock(self, timeout=None, poll=None, max_attempts=None):
1553.5.12 by Martin Pool
New LockDir locking mechanism
468
        """Wait a certain period for a lock.
469
470
        If the lock can be acquired within the bounded time, it
471
        is taken and this returns.  Otherwise, LockContention
472
        is raised.  Either way, this function should return within
473
        approximately `timeout` seconds.  (It may be a bit more if
474
        a transport operation takes a long time to complete.)
2555.3.5 by Martin Pool
Return token directly from LockDir.acquire to avoid unnecessary peek()
475
2555.3.13 by Martin Pool
LockDir cleanups
476
        :param timeout: Approximate maximum amount of time to wait for the
477
        lock, in seconds.
3943.8.1 by Marius Kruger
remove all trailing whitespace from bzr source
478
2555.3.13 by Martin Pool
LockDir cleanups
479
        :param poll: Delay in seconds between retrying the lock.
480
481
        :param max_attempts: Maximum number of times to try to lock.
482
2555.3.5 by Martin Pool
Return token directly from LockDir.acquire to avoid unnecessary peek()
483
        :return: The lock token.
1553.5.12 by Martin Pool
New LockDir locking mechanism
484
        """
1957.1.17 by John Arbash Meinel
Change tests that expect locking to fail to timeout sooner.
485
        if timeout is None:
486
            timeout = _DEFAULT_TIMEOUT_SECONDS
487
        if poll is None:
488
            poll = _DEFAULT_POLL_SECONDS
2555.3.13 by Martin Pool
LockDir cleanups
489
        # XXX: the transport interface doesn't let us guard against operations
490
        # there taking a long time, so the total elapsed time or poll interval
491
        # may be more than was requested.
1553.5.12 by Martin Pool
New LockDir locking mechanism
492
        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
493
        deadline_str = None
1957.1.7 by John Arbash Meinel
Add the ability to report if the lock changes from underneath you
494
        last_info = None
2555.3.13 by Martin Pool
LockDir cleanups
495
        attempt_count = 0
1553.5.12 by Martin Pool
New LockDir locking mechanism
496
        while True:
2555.3.13 by Martin Pool
LockDir cleanups
497
            attempt_count += 1
1553.5.12 by Martin Pool
New LockDir locking mechanism
498
            try:
2555.3.16 by Martin Pool
Clean up patch to make divergence from mainline smaller.
499
                return self.attempt_lock()
500
            except LockContention:
501
                # possibly report the blockage, then try again
502
                pass
503
            # TODO: In a few cases, we find out that there's contention by
504
            # reading the held info and observing that it's not ours.  In
505
            # those cases it's a bit redundant to read it again.  However,
506
            # the normal case (??) is that the rename fails and so we
507
            # don't know who holds the lock.  For simplicity we peek
508
            # always.
509
            new_info = self.peek()
510
            if new_info is not None and new_info != last_info:
511
                if last_info is None:
512
                    start = 'Unable to obtain'
1957.1.9 by John Arbash Meinel
Change default timeouts, and report differently the first failure
513
                else:
2555.3.16 by Martin Pool
Clean up patch to make divergence from mainline smaller.
514
                    start = 'Lock owner changed for'
515
                last_info = new_info
516
                formatted_info = self._format_lock_info(new_info)
517
                if deadline_str is None:
518
                    deadline_str = time.strftime('%H:%M:%S',
519
                                                 time.localtime(deadline))
3441.4.1 by Martin Albisetti
Change locked error to help the user resolve the situation
520
                lock_url = self.transport.abspath(self.path)
2555.3.16 by Martin Pool
Clean up patch to make divergence from mainline smaller.
521
                self._report_function('%s %s\n'
522
                                      '%s\n' # held by
523
                                      '%s\n' # locked ... ago
3441.4.1 by Martin Albisetti
Change locked error to help the user resolve the situation
524
                                      'Will continue to try until %s, unless '
525
                                      'you press Ctrl-C\n'
526
                                      'If you\'re sure that it\'s not being '
527
                                      'modified, use bzr break-lock %s',
2555.3.16 by Martin Pool
Clean up patch to make divergence from mainline smaller.
528
                                      start,
529
                                      formatted_info[0],
530
                                      formatted_info[1],
531
                                      formatted_info[2],
3441.4.1 by Martin Albisetti
Change locked error to help the user resolve the situation
532
                                      deadline_str,
533
                                      lock_url)
2555.3.16 by Martin Pool
Clean up patch to make divergence from mainline smaller.
534
535
            if (max_attempts is not None) and (attempt_count >= max_attempts):
536
                self._trace("exceeded %d attempts")
537
                raise LockContention(self)
538
            if time.time() + poll < deadline:
539
                self._trace("waiting %ss", poll)
540
                time.sleep(poll)
541
            else:
542
                self._trace("timeout after waiting %ss", timeout)
543
                raise LockContention(self)
3943.8.1 by Marius Kruger
remove all trailing whitespace from bzr source
544
2018.5.75 by Andrew Bennetts
Add Repository.{dont_,}leave_lock_in_place.
545
    def leave_in_place(self):
546
        self._locked_via_token = True
547
548
    def dont_leave_in_place(self):
549
        self._locked_via_token = False
1553.5.12 by Martin Pool
New LockDir locking mechanism
550
2279.7.1 by Andrew Bennetts
``LockableFiles.lock_write()`` now accepts a ``token`` keyword argument, so that
551
    def lock_write(self, token=None):
552
        """Wait for and acquire the lock.
3943.8.1 by Marius Kruger
remove all trailing whitespace from bzr source
553
2279.7.1 by Andrew Bennetts
``LockableFiles.lock_write()`` now accepts a ``token`` keyword argument, so that
554
        :param token: if this is already locked, then lock_write will fail
555
            unless the token matches the existing lock.
556
        :returns: a token if this instance supports tokens, otherwise None.
557
        :raises TokenLockingNotSupported: when a token is given but this
558
            instance doesn't support using token locks.
2279.7.7 by Andrew Bennetts
LockDir, Repository and Branch lock token changes from the hpss branch.
559
        :raises MismatchedToken: if the specified token doesn't match the token
2279.7.1 by Andrew Bennetts
``LockableFiles.lock_write()`` now accepts a ``token`` keyword argument, so that
560
            of the existing lock.
2018.5.145 by Andrew Bennetts
Add a brief explanation of what tokens are used for to lock_write docstrings.
561
562
        A token should be passed in if you know that you have locked the object
563
        some other way, and need to synchronise this object's state with that
564
        fact.
3943.8.1 by Marius Kruger
remove all trailing whitespace from bzr source
565
2279.7.1 by Andrew Bennetts
``LockableFiles.lock_write()`` now accepts a ``token`` keyword argument, so that
566
        XXX: docstring duplicated from LockableFiles.lock_write.
567
        """
568
        if token is not None:
569
            self.validate_token(token)
2018.5.75 by Andrew Bennetts
Add Repository.{dont_,}leave_lock_in_place.
570
            self.nonce = token
2279.7.1 by Andrew Bennetts
``LockableFiles.lock_write()`` now accepts a ``token`` keyword argument, so that
571
            self._lock_held = True
572
            self._locked_via_token = True
2018.5.78 by Andrew Bennetts
Implement RemoteRepository.lock_write/unlock to expect and send tokens over the
573
            return token
2279.7.1 by Andrew Bennetts
``LockableFiles.lock_write()`` now accepts a ``token`` keyword argument, so that
574
        else:
2555.3.5 by Martin Pool
Return token directly from LockDir.acquire to avoid unnecessary peek()
575
            return self.wait_lock()
1553.5.44 by Martin Pool
LockableFiles can now call LockDir directly
576
577
    def lock_read(self):
1759.2.1 by Jelmer Vernooij
Fix some types (found using aspell).
578
        """Compatibility-mode shared lock.
1553.5.44 by Martin Pool
LockableFiles can now call LockDir directly
579
3943.8.1 by Marius Kruger
remove all trailing whitespace from bzr source
580
        LockDir doesn't support shared read-only locks, so this
1553.5.54 by Martin Pool
Add LockDir.read_lock fake method
581
        just pretends that the lock is taken but really does nothing.
1553.5.44 by Martin Pool
LockableFiles can now call LockDir directly
582
        """
3943.8.1 by Marius Kruger
remove all trailing whitespace from bzr source
583
        # At the moment Branches are commonly locked for read, but
1553.5.44 by Martin Pool
LockableFiles can now call LockDir directly
584
        # we can't rely on that remotely.  Once this is cleaned up,
3943.8.1 by Marius Kruger
remove all trailing whitespace from bzr source
585
        # reenable this warning to prevent it coming back in
1553.5.44 by Martin Pool
LockableFiles can now call LockDir directly
586
        # -- mbp 20060303
587
        ## warn("LockDir.lock_read falls back to write lock")
1553.5.54 by Martin Pool
Add LockDir.read_lock fake method
588
        if self._lock_held or self._fake_read_lock:
589
            raise LockContention(self)
590
        self._fake_read_lock = True
1553.5.44 by Martin Pool
LockableFiles can now call LockDir directly
591
1957.1.5 by John Arbash Meinel
Create a helper function for formatting lock information
592
    def _format_lock_info(self, info):
593
        """Turn the contents of peek() into something for the user"""
594
        lock_url = self.transport.abspath(self.path)
595
        delta = time.time() - int(info['start_time'])
596
        return [
597
            'lock %s' % (lock_url,),
598
            'held by %(user)s on host %(hostname)s [process #%(pid)s]' % info,
599
            'locked %s' % (format_delta(delta),),
600
            ]
601
2279.7.1 by Andrew Bennetts
``LockableFiles.lock_write()`` now accepts a ``token`` keyword argument, so that
602
    def validate_token(self, token):
603
        if token is not None:
604
            info = self.peek()
605
            if info is None:
606
                # Lock isn't held
607
                lock_token = None
608
            else:
609
                lock_token = info.get('nonce')
610
            if token != lock_token:
611
                raise errors.TokenMismatch(token, lock_token)
2555.3.3 by Martin Pool
Simple lock tracing in LockDir
612
            else:
2555.3.16 by Martin Pool
Clean up patch to make divergence from mainline smaller.
613
                self._trace("revalidated by token %r", token)
2279.7.1 by Andrew Bennetts
``LockableFiles.lock_write()`` now accepts a ``token`` keyword argument, so that
614
2555.3.3 by Martin Pool
Simple lock tracing in LockDir
615
    def _trace(self, format, *args):
616
        if 'lock' not in debug.debug_flags:
617
            return
618
        mutter(str(self) + ": " + (format % args))