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author | Mads Kiilerich <mads@kiilerich.com> |
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date | Wed, 28 Jun 2023 14:23:13 +0200 |
parents | a41eeb877d07 |
children | 5c3d07950bac 0a4efb650b3e |
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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 Olivia Mackall <olivia@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. import errno import os from .i18n import _ from . import ( error, pycompat, util, ) from .utils import stringutil version = 2 GEN_GROUP_ALL = b'all' GEN_GROUP_PRE_FINALIZE = b'prefinalize' GEN_GROUP_POST_FINALIZE = b'postfinalize' def active(func): def _active(self, *args, **kwds): if self._count == 0: raise error.ProgrammingError( b'cannot use transaction when it is already committed/aborted' ) return func(self, *args, **kwds) return _active UNDO_BACKUP = b'%s.backupfiles' UNDO_FILES_MAY_NEED_CLEANUP = [ # legacy entries that might exists on disk from previous version: (b'store', b'%s.narrowspec'), (b'plain', b'%s.narrowspec.dirstate'), (b'plain', b'%s.branch'), (b'plain', b'%s.bookmarks'), (b'store', b'%s.phaseroots'), (b'plain', b'%s.dirstate'), # files actually in uses today: (b'plain', b'%s.desc'), # Always delete undo last to make sure we detect that a clean up is needed if # the process is interrupted. (b'store', b'%s'), ] def cleanup_undo_files(report, vfsmap, undo_prefix=b'undo'): """remove "undo" files used by the rollback logic This is useful to prevent rollback running in situation were it does not make sense. For example after a strip. """ backup_listing = UNDO_BACKUP % undo_prefix backup_entries = [] undo_files = [] svfs = vfsmap[b'store'] try: with svfs(backup_listing) as f: backup_entries = read_backup_files(report, f) except OSError as e: if e.errno != errno.ENOENT: msg = _(b'could not read %s: %s\n') msg %= (svfs.join(backup_listing), stringutil.forcebytestr(e)) report(msg) for location, f, backup_path, c in backup_entries: if location in vfsmap and backup_path: undo_files.append((vfsmap[location], backup_path)) undo_files.append((svfs, backup_listing)) for location, undo_path in UNDO_FILES_MAY_NEED_CLEANUP: undo_files.append((vfsmap[location], undo_path % undo_prefix)) for undovfs, undofile in undo_files: try: undovfs.unlink(undofile) except OSError as e: if e.errno != errno.ENOENT: msg = _(b'error removing %s: %s\n') msg %= (undovfs.join(undofile), stringutil.forcebytestr(e)) report(msg) def _playback( journal, report, opener, vfsmap, entries, backupentries, unlink=True, checkambigfiles=None, ): """rollback a transaction : - truncate files that have been appended to - restore file backups - delete temporary files """ backupfiles = [] def restore_one_backup(vfs, f, b, checkambig): filepath = vfs.join(f) backuppath = vfs.join(b) try: util.copyfile(backuppath, filepath, checkambig=checkambig) backupfiles.append((vfs, b)) except IOError as exc: e_msg = stringutil.forcebytestr(exc) report(_(b"failed to recover %s (%s)\n") % (f, e_msg)) raise # gather all backup files that impact the store # (we need this to detect files that are both backed up and truncated) store_backup = {} for entry in backupentries: location, file_path, backup_path, cache = entry vfs = vfsmap[location] is_store = vfs.join(b'') == opener.join(b'') if is_store and file_path and backup_path: store_backup[file_path] = entry copy_done = set() # truncate all file `f` to offset `o` for f, o in sorted(dict(entries).items()): # if we have a backup for `f`, we should restore it first and truncate # the restored file bck_entry = store_backup.get(f) if bck_entry is not None: location, file_path, backup_path, cache = bck_entry checkambig = False if checkambigfiles: checkambig = (file_path, location) in checkambigfiles restore_one_backup(opener, file_path, backup_path, checkambig) copy_done.add(bck_entry) # truncate the file to its pre-transaction size if o or not unlink: checkambig = checkambigfiles and (f, b'') in checkambigfiles try: fp = opener(f, b'a', checkambig=checkambig) if fp.tell() < o: raise error.Abort( _( b"attempted to truncate %s to %d bytes, but it was " b"already %d bytes\n" ) % (f, o, fp.tell()) ) fp.truncate(o) fp.close() except IOError: report(_(b"failed to truncate %s\n") % f) raise else: # delete empty file try: opener.unlink(f) except FileNotFoundError: pass # restore backed up files and clean up temporary files for entry in backupentries: if entry in copy_done: continue l, f, b, c = entry if l not in vfsmap and c: report(b"couldn't handle %s: unknown cache location %s\n" % (b, l)) vfs = vfsmap[l] try: checkambig = checkambigfiles and (f, l) in checkambigfiles if f and b: restore_one_backup(vfs, f, b, checkambig) else: target = f or b try: vfs.unlink(target) except FileNotFoundError: # This is fine because # # either we are trying to delete the main file, and it is # already deleted. # # or we are trying to delete a temporary file and it is # already deleted. # # in both case, our target result (delete the file) is # already achieved. pass except (IOError, OSError, error.Abort): if not c: raise # cleanup transaction state file and the backups file backuppath = b"%s.backupfiles" % journal if opener.exists(backuppath): opener.unlink(backuppath) opener.unlink(journal) try: for vfs, f in backupfiles: if vfs.exists(f): vfs.unlink(f) except (IOError, OSError, error.Abort): # only pure backup file remains, it is sage to ignore any error pass class transaction(util.transactional): def __init__( self, report, opener, vfsmap, journalname, undoname=None, after=None, createmode=None, validator=None, releasefn=None, checkambigfiles=None, name='<unnamed>', ): """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 * `releasefn`: called after releasing (with transaction and result) `checkambigfiles` is a set of (path, vfs-location) tuples, which determine whether file stat ambiguity should be avoided for corresponded files. """ self._count = 1 self._usages = 1 self._report = report # a vfs to the store content self._opener = opener # a map to access file in various {location -> vfs} vfsmap = vfsmap.copy() vfsmap[b''] = opener # set default value self._vfsmap = vfsmap self._after = after self._offsetmap = {} self._newfiles = set() self._journal = journalname self._journal_files = [] self._undoname = undoname self._queue = [] # A callback to do something just after releasing transaction. if releasefn is None: releasefn = lambda tr, success: None self._releasefn = releasefn self._checkambigfiles = set() if checkambigfiles: self._checkambigfiles.update(checkambigfiles) self._names = [name] # A dict dedicated to precisely tracking the changes introduced in the # transaction. self.changes = {} # a dict of arguments to be passed to hooks self.hookargs = {} self._file = opener.open(self._journal, b"w+") # a list of ('location', 'path', 'backuppath', cache) entries. # - if 'backuppath' is empty, no file existed at backup time # - if 'path' is empty, this is a temporary transaction file # - if 'location' is not empty, the path is outside main opener reach. # use 'location' value as a key in a vfsmap to find the right 'vfs' # (cache is currently unused) self._backupentries = [] self._backupmap = {} self._backupjournal = b"%s.backupfiles" % self._journal self._backupsfile = opener.open(self._backupjournal, b'w') self._backupsfile.write(b'%d\n' % version) # the set of temporary files self._tmp_files = set() if createmode is not None: opener.chmod(self._journal, createmode & 0o666) opener.chmod(self._backupjournal, createmode & 0o666) # hold file generations to be performed on commit self._filegenerators = {} # hold callback 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 = {} # holds callback to call when validating the transaction # should raise exception if anything is wrong self._validatecallback = {} if validator is not None: self._validatecallback[b'001-userhooks'] = validator # hold callback for post transaction close self._postclosecallback = {} # holds callbacks to call during abort self._abortcallback = {} def __repr__(self): name = b'/'.join(self._names) return '<transaction name=%s, count=%d, usages=%d>' % ( name, self._count, self._usages, ) def __del__(self): if self._journal: self._abort() @property def finalized(self): return self._finalizecallback is None @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() for f, o in q: self._addentry(f, o) @active def add(self, file, offset): """record the state of an append-only file before update""" if ( file in self._newfiles or file in self._offsetmap or file in self._backupmap or file in self._tmp_files ): return if self._queue: self._queue[-1].append((file, offset)) return self._addentry(file, offset) def _addentry(self, file, offset): """add a append-only entry to memory and on-disk state""" if ( file in self._newfiles or file in self._offsetmap or file in self._backupmap or file in self._tmp_files ): return if offset: self._offsetmap[file] = offset else: self._newfiles.add(file) # add enough data to the journal to do the truncate self._file.write(b"%s\0%d\n" % (file, offset)) self._file.flush() @active def addbackup(self, file, hardlink=True, location=b'', for_offset=False): """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 `for_offset` is set, we expect a offset for this file to have been previously recorded """ if self._queue: msg = b'cannot use transaction.addbackup inside "group"' raise error.ProgrammingError(msg) if file in self._newfiles or file in self._backupmap: return elif file in self._offsetmap and not for_offset: return elif for_offset and file not in self._offsetmap: msg = ( 'calling `addbackup` with `for_offmap=True`, ' 'but no offset recorded: [%r] %r' ) msg %= (location, file) raise error.ProgrammingError(msg) vfs = self._vfsmap[location] dirname, filename = vfs.split(file) backupfilename = b"%s.backup.%s.bck" % (self._journal, filename) backupfile = vfs.reljoin(dirname, backupfilename) if vfs.exists(file): filepath = vfs.join(file) backuppath = vfs.join(backupfile) # store encoding may result in different directory here. # so we have to ensure the destination directory exist final_dir_name = os.path.dirname(backuppath) util.makedirs(final_dir_name, mode=vfs.createmode, notindexed=True) # then we can copy the backup util.copyfile(filepath, backuppath, hardlink=hardlink) else: backupfile = b'' self._addbackupentry((location, file, backupfile, False)) def _addbackupentry(self, entry): """register a new backup entry and write it to disk""" self._backupentries.append(entry) self._backupmap[entry[1]] = len(self._backupentries) - 1 self._backupsfile.write(b"%s\0%s\0%s\0%d\n" % entry) self._backupsfile.flush() @active def registertmp(self, tmpfile, location=b''): """register a temporary transaction file Such files will be deleted when the transaction exits (on both failure and success). """ self._tmp_files.add(tmpfile) self._addbackupentry((location, b'', tmpfile, False)) @active def addfilegenerator( self, genid, filenames, genfunc, order=0, location=b'', post_finalize=False, ): """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. The `location` arguments may be used to indicate the files are located outside of the the standard directory for transaction. It should match one of the key of the `transaction.vfsmap` dictionary. The `post_finalize` argument can be set to `True` for file generation that must be run after the transaction has been finalized. """ # For now, we are unable to do proper backup and restore of custom vfs # but for bookmarks that are handled outside this mechanism. entry = (order, filenames, genfunc, location, post_finalize) self._filegenerators[genid] = entry @active def removefilegenerator(self, genid): """reverse of addfilegenerator, remove a file generator function""" if genid in self._filegenerators: del self._filegenerators[genid] def _generatefiles(self, suffix=b'', group=GEN_GROUP_ALL): # write files registered for generation any = False if group == GEN_GROUP_ALL: skip_post = skip_pre = False else: skip_pre = group == GEN_GROUP_POST_FINALIZE skip_post = group == GEN_GROUP_PRE_FINALIZE for id, entry in sorted(self._filegenerators.items()): any = True order, filenames, genfunc, location, post_finalize = entry # for generation at closing, check if it's before or after finalize if skip_post and post_finalize: continue elif skip_pre and not post_finalize: continue vfs = self._vfsmap[location] files = [] try: for name in filenames: name += suffix if suffix: self.registertmp(name, location=location) checkambig = False else: self.addbackup(name, location=location) checkambig = (name, location) in self._checkambigfiles files.append( vfs(name, b'w', atomictemp=True, checkambig=checkambig) ) genfunc(*files) for f in files: f.close() # skip discard() loop since we're sure no open file remains del files[:] finally: for f in files: f.discard() return any @active def findoffset(self, file): if file in self._newfiles: return 0 return self._offsetmap.get(file) @active def readjournal(self): self._file.seek(0) entries = [] for l in self._file.readlines(): file, troffset = l.split(b'\0') entries.append((file, int(troffset))) return entries @active def replace(self, file, offset): """ replace can only replace already committed entries that are not pending in the queue """ if file in self._newfiles: if not offset: return self._newfiles.remove(file) self._offsetmap[file] = offset elif file in self._offsetmap: if not offset: del self._offsetmap[file] self._newfiles.add(file) else: self._offsetmap[file] = offset else: raise KeyError(file) self._file.write(b"%s\0%d\n" % (file, offset)) self._file.flush() @active def nest(self, name='<unnamed>'): self._count += 1 self._usages += 1 self._names.append(name) return self def release(self): if self._count > 0: self._usages -= 1 if self._names: self._names.pop() # 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 The transaction will be given as callback's first argument. 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) self._anypending = self._anypending or any self._anypending |= self._generatefiles(suffix=b'.pending') return self._anypending @active def hasfinalize(self, category): """check is a callback already exist for a category""" return category in self._finalizecallback @active def addfinalize(self, category, callback): """add a callback to be called when the transaction is closed The transaction will be given as callback's first argument. Category is a unique identifier to allow overwriting old callbacks with newer callbacks. """ self._finalizecallback[category] = callback @active def addpostclose(self, category, callback): """add or replace a callback to be called after the transaction closed The transaction will be given as callback's first argument. Category is a unique identifier to allow overwriting an old callback with a newer callback. """ self._postclosecallback[category] = callback @active def getpostclose(self, category): """return a postclose callback added before, or None""" return self._postclosecallback.get(category, None) @active def addabort(self, category, callback): """add a callback to be called when the transaction is aborted. The transaction will be given as the first argument to the callback. Category is a unique identifier to allow overwriting an old callback with a newer callback. """ self._abortcallback[category] = callback @active def addvalidator(self, category, callback): """adds a callback to be called when validating the transaction. The transaction will be given as the first argument to the callback. callback should raise exception if to abort transaction""" self._validatecallback[category] = callback @active def close(self): '''commit the transaction''' if self._count == 1: for category in sorted(self._validatecallback): self._validatecallback[category](self) self._validatecallback = None # Help prevent cycles. self._generatefiles(group=GEN_GROUP_PRE_FINALIZE) while self._finalizecallback: callbacks = self._finalizecallback self._finalizecallback = {} categories = sorted(callbacks) for cat in categories: callbacks[cat](self) # Prevent double usage and help clear cycles. self._finalizecallback = None self._generatefiles(group=GEN_GROUP_POST_FINALIZE) self._count -= 1 if self._count != 0: return self._file.close() self._backupsfile.close() # cleanup temporary files for l, f, b, c in self._backupentries: if l not in self._vfsmap and c: self._report( b"couldn't remove %s: unknown cache location %s\n" % (b, l) ) continue vfs = self._vfsmap[l] if not f and b and vfs.exists(b): try: vfs.unlink(b) except (IOError, OSError, error.Abort) as inst: if not c: raise # Abort may be raise by read only opener self._report( b"couldn't remove %s: %s\n" % (vfs.join(b), inst) ) self._offsetmap = {} self._newfiles = set() self._writeundo() if self._after: self._after() self._after = None # Help prevent cycles. if self._opener.isfile(self._backupjournal): self._opener.unlink(self._backupjournal) if self._opener.isfile(self._journal): self._opener.unlink(self._journal) for l, _f, b, c in self._backupentries: if l not in self._vfsmap and c: self._report( b"couldn't remove %s: unknown cache location" b"%s\n" % (b, l) ) continue vfs = self._vfsmap[l] if b and vfs.exists(b): try: vfs.unlink(b) except (IOError, OSError, error.Abort) as inst: if not c: raise # Abort may be raise by read only opener self._report( b"couldn't remove %s: %s\n" % (vfs.join(b), inst) ) self._backupentries = [] self._journal = None self._releasefn(self, True) # notify success of closing transaction self._releasefn = None # Help prevent cycles. # run post close action categories = sorted(self._postclosecallback) for cat in categories: self._postclosecallback[cat](self) # Prevent double usage and help clear cycles. self._postclosecallback = None @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() @active def add_journal(self, vfs_id, path): self._journal_files.append((vfs_id, path)) def _writeundo(self): """write transaction data for possible future undo call""" if self._undoname is None: return cleanup_undo_files( self._report, self._vfsmap, undo_prefix=self._undoname, ) def undoname(fn: bytes) -> bytes: base, name = os.path.split(fn) assert name.startswith(self._journal) new_name = name.replace(self._journal, self._undoname, 1) return os.path.join(base, new_name) undo_backup_path = b"%s.backupfiles" % self._undoname undobackupfile = self._opener.open(undo_backup_path, b'w') undobackupfile.write(b'%d\n' % version) for l, f, b, c in self._backupentries: if not f: # temporary file continue if not b: u = b'' else: if l not in self._vfsmap and c: self._report( b"couldn't remove %s: unknown cache location" b"%s\n" % (b, l) ) continue vfs = self._vfsmap[l] u = undoname(b) util.copyfile(vfs.join(b), vfs.join(u), hardlink=True) undobackupfile.write(b"%s\0%s\0%s\0%d\n" % (l, f, u, c)) undobackupfile.close() for vfs, src in self._journal_files: dest = undoname(src) # if src and dest refer to a same file, vfs.rename is a no-op, # leaving both src and dest on disk. delete dest to make sure # the rename couldn't be such a no-op. vfs.tryunlink(dest) try: vfs.rename(src, dest) except FileNotFoundError: # journal file does not yet exist pass def _abort(self): entries = self.readjournal() self._count = 0 self._usages = 0 self._file.close() self._backupsfile.close() quick = self._can_quick_abort(entries) try: if not quick: self._report(_(b"transaction abort!\n")) for cat in sorted(self._abortcallback): self._abortcallback[cat](self) # Prevent double usage and help clear cycles. self._abortcallback = None if quick: self._do_quick_abort(entries) else: self._do_full_abort(entries) finally: self._journal = None self._releasefn(self, False) # notify failure of transaction self._releasefn = None # Help prevent cycles. def _can_quick_abort(self, entries): """False if any semantic content have been written on disk True if nothing, except temporary files has been writen on disk.""" if entries: return False for e in self._backupentries: if e[1]: return False return True def _do_quick_abort(self, entries): """(Silently) do a quick cleanup (see _can_quick_abort)""" assert self._can_quick_abort(entries) tmp_files = [e for e in self._backupentries if not e[1]] for vfs_id, old_path, tmp_path, xxx in tmp_files: vfs = self._vfsmap[vfs_id] try: vfs.unlink(tmp_path) except FileNotFoundError: pass if self._backupjournal: self._opener.unlink(self._backupjournal) if self._journal: self._opener.unlink(self._journal) def _do_full_abort(self, entries): """(Noisily) rollback all the change introduced by the transaction""" try: _playback( self._journal, self._report, self._opener, self._vfsmap, entries, self._backupentries, False, checkambigfiles=self._checkambigfiles, ) self._report(_(b"rollback completed\n")) except BaseException as exc: self._report(_(b"rollback failed - please run hg recover\n")) self._report( _(b"(failure reason: %s)\n") % stringutil.forcebytestr(exc) ) BAD_VERSION_MSG = _( b"journal was created by a different version of Mercurial\n" ) def read_backup_files(report, fp): """parse an (already open) backup file an return contained backup entries entries are in the form: (location, file, backupfile, xxx) :location: the vfs identifier (vfsmap's key) :file: original file path (in the vfs) :backupfile: path of the backup (in the vfs) :cache: a boolean currently always set to False """ lines = fp.readlines() backupentries = [] if lines: ver = lines[0][:-1] if ver != (b'%d' % version): report(BAD_VERSION_MSG) else: for line in lines[1:]: if line: # Shave off the trailing newline line = line[:-1] l, f, b, c = line.split(b'\0') backupentries.append((l, f, b, bool(c))) return backupentries def rollback( opener, vfsmap, file, report, checkambigfiles=None, skip_journal_pattern=None, ): """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. `checkambigfiles` is a set of (path, vfs-location) tuples, which determine whether file stat ambiguity should be avoided at restoring corresponded files. """ entries = [] backupentries = [] with opener.open(file) as fp: lines = fp.readlines() for l in lines: try: f, o = l.split(b'\0') entries.append((f, int(o))) except ValueError: report( _(b"couldn't read journal entry %r!\n") % pycompat.bytestr(l) ) backupjournal = b"%s.backupfiles" % file if opener.exists(backupjournal): with opener.open(backupjournal) as fp: backupentries = read_backup_files(report, fp) if skip_journal_pattern is not None: keep = lambda x: not skip_journal_pattern.match(x[1]) backupentries = [x for x in backupentries if keep(x)] _playback( file, report, opener, vfsmap, entries, backupentries, checkambigfiles=checkambigfiles, )