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# transaction.py - simple journaling scheme for mercurial
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#
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# This transaction scheme is intended to gracefully handle program
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# errors and interruptions. More serious failures like system crashes
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# can be recovered with an fsck-like tool. As the whole repository is
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# effectively log-structured, this should amount to simply truncating
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# anything that isn't referenced in the changelog.
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#
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# Copyright 2005, 2006 Matt Mackall <mpm@selenic.com>
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#
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# This software may be used and distributed according to the terms of the
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# GNU General Public License version 2 or any later version.
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from i18n import _
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import errno
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import error, util
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def active(func):
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def _active(self, *args, **kwds):
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if self.count == 0:
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raise error.Abort(_(
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'cannot use transaction when it is already committed/aborted'))
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return func(self, *args, **kwds)
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return _active
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def _playback(journal, report, opener, entries, backupentries, unlink=True):
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for f, o, _ignore in entries:
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if o or not unlink:
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try:
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fp = opener(f, 'a')
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fp.truncate(o)
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fp.close()
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except IOError:
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report(_("failed to truncate %s\n") % f)
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raise
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else:
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try:
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opener.unlink(f)
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except (IOError, OSError), inst:
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if inst.errno != errno.ENOENT:
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raise
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backupfiles = []
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for f, b, _ignore in backupentries:
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filepath = opener.join(f)
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backuppath = opener.join(b)
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try:
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util.copyfile(backuppath, filepath)
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backupfiles.append(b)
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except IOError:
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report(_("failed to recover %s\n") % f)
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raise
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opener.unlink(journal)
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backuppath = "%s.backupfiles" % journal
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if opener.exists(backuppath):
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opener.unlink(backuppath)
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for f in backupfiles:
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opener.unlink(f)
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class transaction(object):
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def __init__(self, report, opener, journal, after=None, createmode=None,
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onclose=None, onabort=None):
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"""Begin a new transaction
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Begins a new transaction that allows rolling back writes in the event of
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an exception.
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* `after`: called after the transaction has been committed
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* `createmode`: the mode of the journal file that will be created
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* `onclose`: called as the transaction is closing, but before it is
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closed
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* `onabort`: called as the transaction is aborting, but before any files
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have been truncated
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"""
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self.count = 1
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self.usages = 1
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self.report = report
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self.opener = opener
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self.after = after
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self.onclose = onclose
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self.onabort = onabort
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self.entries = []
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self.backupentries = []
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self.map = {}
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self.backupmap = {}
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self.journal = journal
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self._queue = []
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# a dict of arguments to be passed to hooks
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self.hookargs = {}
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self.backupjournal = "%s.backupfiles" % journal
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self.file = opener.open(self.journal, "w")
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self.backupsfile = opener.open(self.backupjournal, 'w')
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if createmode is not None:
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opener.chmod(self.journal, createmode & 0666)
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opener.chmod(self.backupjournal, createmode & 0666)
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# hold file generations to be performed on commit
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self._filegenerators = {}
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def __del__(self):
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if self.journal:
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self._abort()
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@active
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def startgroup(self):
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self._queue.append(([], []))
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@active
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def endgroup(self):
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q = self._queue.pop()
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self.entries.extend(q[0])
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self.backupentries.extend(q[1])
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offsets = []
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backups = []
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for f, o, _data in q[0]:
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offsets.append((f, o))
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for f, b, _data in q[1]:
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backups.append((f, b))
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d = ''.join(['%s\0%d\n' % (f, o) for f, o in offsets])
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self.file.write(d)
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self.file.flush()
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d = ''.join(['%s\0%s\0' % (f, b) for f, b in backups])
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self.backupsfile.write(d)
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self.backupsfile.flush()
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@active
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def add(self, file, offset, data=None):
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if file in self.map or file in self.backupmap:
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return
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if self._queue:
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self._queue[-1][0].append((file, offset, data))
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return
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self.entries.append((file, offset, data))
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self.map[file] = len(self.entries) - 1
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# add enough data to the journal to do the truncate
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self.file.write("%s\0%d\n" % (file, offset))
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self.file.flush()
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@active
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def addbackup(self, file, hardlink=True, vfs=None):
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"""Adds a backup of the file to the transaction
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Calling addbackup() creates a hardlink backup of the specified file
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that is used to recover the file in the event of the transaction
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aborting.
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* `file`: the file path, relative to .hg/store
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* `hardlink`: use a hardlink to quickly create the backup
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"""
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if file in self.map or file in self.backupmap:
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return
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backupfile = "%s.backup.%s" % (self.journal, file)
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if vfs is None:
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vfs = self.opener
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if vfs.exists(file):
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filepath = vfs.join(file)
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backuppath = self.opener.join(backupfile)
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util.copyfiles(filepath, backuppath, hardlink=hardlink)
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else:
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self.add(file, 0)
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return
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if self._queue:
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self._queue[-1][1].append((file, backupfile))
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return
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self.backupentries.append((file, backupfile, None))
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self.backupmap[file] = len(self.backupentries) - 1
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self.backupsfile.write("%s\0%s\0" % (file, backupfile))
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self.backupsfile.flush()
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@active
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def addfilegenerator(self, genid, filenames, genfunc, order=0, vfs=None):
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"""add a function to generates some files at transaction commit
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The `genfunc` argument is a function capable of generating proper
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content of each entry in the `filename` tuple.
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At transaction close time, `genfunc` will be called with one file
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object argument per entries in `filenames`.
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The transaction itself is responsible for the backup, creation and
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final write of such file.
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The `genid` argument is used to ensure the same set of file is only
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generated once. Call to `addfilegenerator` for a `genid` already
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present will overwrite the old entry.
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The `order` argument may be used to control the order in which multiple
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generator will be executed.
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"""
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# For now, we are unable to do proper backup and restore of custom vfs
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# but for bookmarks that are handled outside this mechanism.
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assert vfs is None or filenames == ('bookmarks',)
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self._filegenerators[genid] = (order, filenames, genfunc, vfs)
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@active
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def find(self, file):
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if file in self.map:
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return self.entries[self.map[file]]
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if file in self.backupmap:
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return self.backupentries[self.backupmap[file]]
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return None
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@active
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def replace(self, file, offset, data=None):
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'''
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replace can only replace already committed entries
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that are not pending in the queue
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'''
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if file not in self.map:
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raise KeyError(file)
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index = self.map[file]
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self.entries[index] = (file, offset, data)
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self.file.write("%s\0%d\n" % (file, offset))
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self.file.flush()
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@active
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def nest(self):
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self.count += 1
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self.usages += 1
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return self
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def release(self):
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if self.count > 0:
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self.usages -= 1
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# if the transaction scopes are left without being closed, fail
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if self.count > 0 and self.usages == 0:
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self._abort()
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def running(self):
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return self.count > 0
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@active
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def close(self):
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'''commit the transaction'''
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# write files registered for generation
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for entry in sorted(self._filegenerators.values()):
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order, filenames, genfunc, vfs = entry
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if vfs is None:
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vfs = self.opener
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files = []
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try:
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for name in filenames:
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# Some files are already backed up when creating the
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# localrepo. Until this is properly fixed we disable the
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# backup for them.
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if name not in ('phaseroots', 'bookmarks'):
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self.addbackup(name)
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files.append(vfs(name, 'w', atomictemp=True))
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genfunc(*files)
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finally:
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for f in files:
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f.close()
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if self.count == 1 and self.onclose is not None:
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self.onclose()
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self.count -= 1
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if self.count != 0:
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return
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self.file.close()
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self.backupsfile.close()
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self.entries = []
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if self.after:
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self.after()
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if self.opener.isfile(self.journal):
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self.opener.unlink(self.journal)
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if self.opener.isfile(self.backupjournal):
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self.opener.unlink(self.backupjournal)
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for _f, b, _ignore in self.backupentries:
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self.opener.unlink(b)
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self.backupentries = []
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self.journal = None
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@active
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def abort(self):
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'''abort the transaction (generally called on error, or when the
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transaction is not explicitly committed before going out of
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scope)'''
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self._abort()
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def _abort(self):
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self.count = 0
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self.usages = 0
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self.file.close()
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self.backupsfile.close()
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if self.onabort is not None:
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self.onabort()
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try:
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if not self.entries and not self.backupentries:
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if self.journal:
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self.opener.unlink(self.journal)
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if self.backupjournal:
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self.opener.unlink(self.backupjournal)
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return
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self.report(_("transaction abort!\n"))
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try:
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_playback(self.journal, self.report, self.opener,
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self.entries, self.backupentries, False)
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self.report(_("rollback completed\n"))
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except Exception:
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self.report(_("rollback failed - please run hg recover\n"))
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finally:
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self.journal = None
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def rollback(opener, file, report):
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"""Rolls back the transaction contained in the given file
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Reads the entries in the specified file, and the corresponding
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'*.backupfiles' file, to recover from an incomplete transaction.
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* `file`: a file containing a list of entries, specifying where
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to truncate each file. The file should contain a list of
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file\0offset pairs, delimited by newlines. The corresponding
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'*.backupfiles' file should contain a list of file\0backupfile
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pairs, delimited by \0.
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"""
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entries = []
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backupentries = []
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fp = opener.open(file)
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lines = fp.readlines()
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fp.close()
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for l in lines:
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try:
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f, o = l.split('\0')
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entries.append((f, int(o), None))
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except ValueError:
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report(_("couldn't read journal entry %r!\n") % l)
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backupjournal = "%s.backupfiles" % file
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if opener.exists(backupjournal):
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fp = opener.open(backupjournal)
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data = fp.read()
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if len(data) > 0:
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parts = data.split('\0')
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# Skip the final part, since it's just a trailing empty space
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for i in xrange(0, len(parts) - 1, 2):
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f, b = parts[i:i + 2]
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backupentries.append((f, b, None))
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_playback(file, report, opener, entries, backupentries)
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