Mercurial > hg
view mercurial/transaction.py @ 23250:8919dc7f2dbb
transaction: document startgroup and endgroup
These enigmatic methods are only used in repair. We document them to clarify
there purpose and user.
author | Pierre-Yves David <pierre-yves.david@fb.com> |
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date | Wed, 05 Nov 2014 10:00:15 +0000 |
parents | 84720eab4fbd |
children | 85c634ff395a |
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# transaction.py - simple journaling scheme for mercurial # # This transaction scheme is intended to gracefully handle program # errors and interruptions. More serious failures like system crashes # can be recovered with an fsck-like tool. As the whole repository is # effectively log-structured, this should amount to simply truncating # anything that isn't referenced in the changelog. # # Copyright 2005, 2006 Matt Mackall <mpm@selenic.com> # # This software may be used and distributed according to the terms of the # GNU General Public License version 2 or any later version. from i18n import _ import errno import error, util version = 1 def active(func): def _active(self, *args, **kwds): if self.count == 0: raise error.Abort(_( 'cannot use transaction when it is already committed/aborted')) return func(self, *args, **kwds) return _active def _playback(journal, report, opener, entries, backupentries, unlink=True): for f, o, _ignore in entries: if o or not unlink: try: fp = opener(f, 'a') fp.truncate(o) fp.close() except IOError: report(_("failed to truncate %s\n") % f) raise else: try: opener.unlink(f) except (IOError, OSError), inst: if inst.errno != errno.ENOENT: raise backupfiles = [] for f, b in backupentries: filepath = opener.join(f) backuppath = opener.join(b) try: util.copyfile(backuppath, filepath) backupfiles.append(b) except IOError: report(_("failed to recover %s\n") % f) raise opener.unlink(journal) backuppath = "%s.backupfiles" % journal if opener.exists(backuppath): opener.unlink(backuppath) for f in backupfiles: opener.unlink(f) class transaction(object): def __init__(self, report, opener, journal, after=None, createmode=None, onclose=None, onabort=None): """Begin a new transaction Begins a new transaction that allows rolling back writes in the event of an exception. * `after`: called after the transaction has been committed * `createmode`: the mode of the journal file that will be created * `onclose`: called as the transaction is closing, but before it is closed * `onabort`: called as the transaction is aborting, but before any files have been truncated """ self.count = 1 self.usages = 1 self.report = report self.opener = opener self.after = after self.onclose = onclose self.onabort = onabort self.entries = [] self.map = {} # a list of ('path', 'backuppath') entries. self._backupentries = [] self._backupmap = {} self.journal = journal self._queue = [] # a dict of arguments to be passed to hooks self.hookargs = {} self._backupjournal = "%s.backupfiles" % journal self.file = opener.open(self.journal, "w") self._backupsfile = opener.open(self._backupjournal, 'w') self._backupsfile.write('%d\n' % version) if createmode is not None: opener.chmod(self.journal, createmode & 0666) opener.chmod(self._backupjournal, createmode & 0666) # hold file generations to be performed on commit self._filegenerators = {} # hold callbalk to write pending data for hooks self._pendingcallback = {} # True is any pending data have been written ever self._anypending = False # holds callback to call when writing the transaction self._finalizecallback = {} # hold callbalk for post transaction close self._postclosecallback = {} def __del__(self): if self.journal: self._abort() @active def startgroup(self): """delay registration of file entry This is used by strip to delay vision of strip offset. The transaction sees either none or all of the strip actions to be done.""" self._queue.append(([], [])) @active def endgroup(self): """apply delayed registration of file entry. This is used by strip to delay vision of strip offset. The transaction sees either none or all of the strip actions to be done.""" q = self._queue.pop() self.entries.extend(q[0]) self._backupentries.extend(q[1]) offsets = [] backups = [] for f, o, _data in q[0]: offsets.append((f, o)) for f, b in q[1]: backups.append((f, b)) d = ''.join(['%s\0%d\n' % (f, o) for f, o in offsets]) self.file.write(d) self.file.flush() d = ''.join(['%s\0%s\n' % (f, b) for f, b in backups]) self._backupsfile.write(d) self._backupsfile.flush() @active def add(self, file, offset, data=None): if file in self.map or file in self._backupmap: return if self._queue: self._queue[-1][0].append((file, offset, data)) return self.entries.append((file, offset, data)) self.map[file] = len(self.entries) - 1 # add enough data to the journal to do the truncate self.file.write("%s\0%d\n" % (file, offset)) self.file.flush() @active def addbackup(self, file, hardlink=True, vfs=None): """Adds a backup of the file to the transaction Calling addbackup() creates a hardlink backup of the specified file that is used to recover the file in the event of the transaction aborting. * `file`: the file path, relative to .hg/store * `hardlink`: use a hardlink to quickly create the backup """ if file in self.map or file in self._backupmap: return backupfile = "%s.backup.%s" % (self.journal, file) if vfs is None: vfs = self.opener if vfs.exists(file): filepath = vfs.join(file) backuppath = self.opener.join(backupfile) util.copyfiles(filepath, backuppath, hardlink=hardlink) else: self.add(file, 0) return if self._queue: self._queue[-1][1].append((file, backupfile)) return self._backupentries.append((file, backupfile)) self._backupmap[file] = len(self._backupentries) - 1 self._backupsfile.write("%s\0%s\n" % (file, backupfile)) self._backupsfile.flush() @active def addfilegenerator(self, genid, filenames, genfunc, order=0, vfs=None): """add a function to generates some files at transaction commit The `genfunc` argument is a function capable of generating proper content of each entry in the `filename` tuple. At transaction close time, `genfunc` will be called with one file object argument per entries in `filenames`. The transaction itself is responsible for the backup, creation and final write of such file. The `genid` argument is used to ensure the same set of file is only generated once. Call to `addfilegenerator` for a `genid` already present will overwrite the old entry. The `order` argument may be used to control the order in which multiple generator will be executed. """ # For now, we are unable to do proper backup and restore of custom vfs # but for bookmarks that are handled outside this mechanism. assert vfs is None or filenames == ('bookmarks',) self._filegenerators[genid] = (order, filenames, genfunc, vfs) def _generatefiles(self): # write files registered for generation for entry in sorted(self._filegenerators.values()): order, filenames, genfunc, vfs = entry if vfs is None: vfs = self.opener files = [] try: for name in filenames: # Some files are already backed up when creating the # localrepo. Until this is properly fixed we disable the # backup for them. if name not in ('phaseroots', 'bookmarks'): self.addbackup(name) files.append(vfs(name, 'w', atomictemp=True)) genfunc(*files) finally: for f in files: f.close() @active def find(self, file): if file in self.map: return self.entries[self.map[file]] if file in self._backupmap: return self._backupentries[self._backupmap[file]] return None @active def replace(self, file, offset, data=None): ''' replace can only replace already committed entries that are not pending in the queue ''' if file not in self.map: raise KeyError(file) index = self.map[file] self.entries[index] = (file, offset, data) self.file.write("%s\0%d\n" % (file, offset)) self.file.flush() @active def nest(self): self.count += 1 self.usages += 1 return self def release(self): if self.count > 0: self.usages -= 1 # if the transaction scopes are left without being closed, fail if self.count > 0 and self.usages == 0: self._abort() def running(self): return self.count > 0 def addpending(self, category, callback): """add a callback to be called when the transaction is pending Category is a unique identifier to allow overwriting an old callback with a newer callback. """ self._pendingcallback[category] = callback @active def writepending(self): '''write pending file to temporary version This is used to allow hooks to view a transaction before commit''' categories = sorted(self._pendingcallback) for cat in categories: # remove callback since the data will have been flushed any = self._pendingcallback.pop(cat)() self._anypending = self._anypending or any return self._anypending @active def addfinalize(self, category, callback): """add a callback to be called when the transaction is closed Category is a unique identifier to allow overwriting old callbacks with newer callbacks. """ self._finalizecallback[category] = callback @active def addpostclose(self, category, callback): """add a callback to be called after the transaction is closed Category is a unique identifier to allow overwriting an old callback with a newer callback. """ self._postclosecallback[category] = callback @active def close(self): '''commit the transaction''' if self.count == 1 and self.onclose is not None: self._generatefiles() categories = sorted(self._finalizecallback) for cat in categories: self._finalizecallback[cat]() self.onclose() self.count -= 1 if self.count != 0: return self.file.close() self._backupsfile.close() self.entries = [] if self.after: self.after() if self.opener.isfile(self.journal): self.opener.unlink(self.journal) if self.opener.isfile(self._backupjournal): self.opener.unlink(self._backupjournal) for _f, b in self._backupentries: self.opener.unlink(b) self._backupentries = [] self.journal = None # run post close action categories = sorted(self._postclosecallback) for cat in categories: self._postclosecallback[cat]() @active def abort(self): '''abort the transaction (generally called on error, or when the transaction is not explicitly committed before going out of scope)''' self._abort() def _abort(self): self.count = 0 self.usages = 0 self.file.close() self._backupsfile.close() if self.onabort is not None: self.onabort() try: if not self.entries and not self._backupentries: if self.journal: self.opener.unlink(self.journal) if self._backupjournal: self.opener.unlink(self._backupjournal) return self.report(_("transaction abort!\n")) try: _playback(self.journal, self.report, self.opener, self.entries, self._backupentries, False) self.report(_("rollback completed\n")) except Exception: self.report(_("rollback failed - please run hg recover\n")) finally: self.journal = None def rollback(opener, file, report): """Rolls back the transaction contained in the given file Reads the entries in the specified file, and the corresponding '*.backupfiles' file, to recover from an incomplete transaction. * `file`: a file containing a list of entries, specifying where to truncate each file. The file should contain a list of file\0offset pairs, delimited by newlines. The corresponding '*.backupfiles' file should contain a list of file\0backupfile pairs, delimited by \0. """ entries = [] backupentries = [] fp = opener.open(file) lines = fp.readlines() fp.close() for l in lines: try: f, o = l.split('\0') entries.append((f, int(o), None)) except ValueError: report(_("couldn't read journal entry %r!\n") % l) backupjournal = "%s.backupfiles" % file if opener.exists(backupjournal): fp = opener.open(backupjournal) lines = fp.readlines() if lines: ver = lines[0][:-1] if ver == str(version): for line in lines[1:]: if line: # Shave off the trailing newline line = line[:-1] f, b = line.split('\0') backupentries.append((f, b)) else: report(_("journal was created by a newer version of " "Mercurial")) _playback(file, report, opener, entries, backupentries)