Mercurial > hg
view mercurial/transaction.py @ 24735:07200e3332a1
tags: extract .hgtags filenodes cache to a standalone file
Resolution of .hgtags filenodes values has historically been a
performance pain point for large repositories, where reading individual
manifests can take over 100ms. Multiplied by hundreds or even thousands
of heads and resolving .hgtags filenodes becomes a performance issue.
This patch establishes a standalone cache file holding the .hgtags
filenodes for each changeset. After this patch, the .hgtags filenode
for any particular changeset should only have to be computed once
during the lifetime of the repository.
The introduced hgtagsfnodes1 cache file is modeled after the rev branch
cache: the cache is effectively an array of entries consisting of a
changeset fragment and the filenode for a revision. The file grows in
proportion to the length of the repository (24 bytes per changeset) and
is truncated when the repository is stripped. The file is not written
unless tag info is requested and tags have changed since last time.
This patch partially addresses issue4550. Future patches will split the
"tags" cache file into per-filter files and will refactor the cache
format to not capture the .hgtags fnodes, as these are now stored in
the hgtagsfnodes1 cache. This patch is capable of standing alone. We
should not have to wait on the tags cache filter split and format
refactor for this patch to land.
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Wed, 15 Apr 2015 17:42:38 -0400 |
parents | 774ee9800146 |
children | 0d0ed375fbdf fd905b2bea59 |
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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 = 2 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, vfsmap, 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 l, f, b, c in backupentries: if l not in vfsmap and c: report("couldn't handle %s: unknown cache location %s\n" % (b, l)) vfs = vfsmap[l] try: if f and b: filepath = vfs.join(f) backuppath = vfs.join(b) try: util.copyfile(backuppath, filepath) backupfiles.append(b) except IOError: report(_("failed to recover %s\n") % f) else: target = f or b try: vfs.unlink(target) except (IOError, OSError), inst: if inst.errno != errno.ENOENT: raise except (IOError, OSError, util.Abort), inst: if not c: raise opener.unlink(journal) backuppath = "%s.backupfiles" % journal if opener.exists(backuppath): opener.unlink(backuppath) try: for f in backupfiles: if opener.exists(f): opener.unlink(f) except (IOError, OSError, util.Abort), inst: # only pure backup file remains, it is sage to ignore any error pass class transaction(object): def __init__(self, report, opener, vfsmap, journalname, undoname=None, after=None, createmode=None, validator=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 """ 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[''] = opener # set default value self._vfsmap = vfsmap self.after = after self.entries = [] self.map = {} self.journal = journalname self.undoname = undoname self._queue = [] # A callback to validate transaction content before closing it. # should raise exception is anything is wrong. # target user is repository hooks. if validator is None: validator = lambda tr: None self.validator = validator # a dict of arguments to be passed to hooks self.hookargs = {} self.file = opener.open(self.journal, "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 = "%s.backupfiles" % self.journal 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 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 = {} # hold callback for post transaction close self._postclosecallback = {} # holds callbacks to call during abort self._abortcallback = {} 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() for f, o, data in q: self._addentry(f, o, data) @active def add(self, file, offset, data=None): """record the state of an append-only file before update""" if file in self.map or file in self._backupmap: return if self._queue: self._queue[-1].append((file, offset, data)) return self._addentry(file, offset, data) def _addentry(self, file, offset, data): """add a append-only entry to memory and on-disk state""" if file in self.map or file in self._backupmap: 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, location=''): """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 self._queue: msg = 'cannot use transaction.addbackup inside "group"' raise RuntimeError(msg) if file in self.map or file in self._backupmap: return vfs = self._vfsmap[location] dirname, filename = vfs.split(file) backupfilename = "%s.backup.%s" % (self.journal, filename) backupfile = vfs.reljoin(dirname, backupfilename) if vfs.exists(file): filepath = vfs.join(file) backuppath = vfs.join(backupfile) util.copyfile(filepath, backuppath, hardlink=hardlink) else: backupfile = '' 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[file] = len(self._backupentries) - 1 self._backupsfile.write("%s\0%s\0%s\0%d\n" % entry) self._backupsfile.flush() @active def registertmp(self, tmpfile, location=''): """register a temporary transaction file Such files will be deleted when the transaction exits (on both failure and success). """ self._addbackupentry((location, '', tmpfile, False)) @active def addfilegenerator(self, genid, filenames, genfunc, order=0, location=''): """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. """ # For now, we are unable to do proper backup and restore of custom vfs # but for bookmarks that are handled outside this mechanism. self._filegenerators[genid] = (order, filenames, genfunc, location) def _generatefiles(self, suffix=''): # write files registered for generation any = False for entry in sorted(self._filegenerators.values()): any = True order, filenames, genfunc, location = entry vfs = self._vfsmap[location] files = [] try: for name in filenames: name += suffix if suffix: self.registertmp(name, location=location) else: self.addbackup(name, location=location) files.append(vfs(name, 'w', atomictemp=True)) genfunc(*files) finally: for f in files: f.close() return any @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 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='.pending') return self._anypending @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 a callback to be called after the transaction is 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 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 close(self): '''commit the transaction''' if self.count == 1: self.validator(self) # will raise exception if needed self._generatefiles() categories = sorted(self._finalizecallback) for cat in categories: self._finalizecallback[cat](self) 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("couldn't remote %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, util.Abort), inst: if not c: raise # Abort may be raise by read only opener self.report("couldn't remote %s: %s\n" % (vfs.join(b), inst)) self.entries = [] self._writeundo() 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 l, _f, b, c in self._backupentries: if l not in self._vfsmap and c: self.report("couldn't remote %s: unknown cache location" "%s\n" % (b, l)) continue vfs = self._vfsmap[l] if b and vfs.exists(b): try: vfs.unlink(b) except (IOError, OSError, util.Abort), inst: if not c: raise # Abort may be raise by read only opener self.report("couldn't remote %s: %s\n" % (vfs.join(b), inst)) self._backupentries = [] self.journal = None # run post close action categories = sorted(self._postclosecallback) for cat in categories: self._postclosecallback[cat](self) @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 _writeundo(self): """write transaction data for possible future undo call""" if self.undoname is None: return undobackupfile = self.opener.open("%s.backupfiles" % self.undoname, 'w') undobackupfile.write('%d\n' % version) for l, f, b, c in self._backupentries: if not f: # temporary file continue if not b: u = '' else: if l not in self._vfsmap and c: self.report("couldn't remote %s: unknown cache location" "%s\n" % (b, l)) continue vfs = self._vfsmap[l] base, name = vfs.split(b) assert name.startswith(self.journal), name uname = name.replace(self.journal, self.undoname, 1) u = vfs.reljoin(base, uname) util.copyfile(vfs.join(b), vfs.join(u), hardlink=True) undobackupfile.write("%s\0%s\0%s\0%d\n" % (l, f, u, c)) undobackupfile.close() def _abort(self): self.count = 0 self.usages = 0 self.file.close() self._backupsfile.close() 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: for cat in sorted(self._abortcallback): self._abortcallback[cat](self) _playback(self.journal, self.report, self.opener, self._vfsmap, 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, vfsmap, 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] l, f, b, c = line.split('\0') backupentries.append((l, f, b, bool(c))) else: report(_("journal was created by a different version of " "Mercurial\n")) _playback(file, report, opener, vfsmap, entries, backupentries)