git_cache.py

#!/usr/bin/env python
# Copyright 2014 The Chromium Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""A git command for managing a local cache of git repositories."""

from __future__ import print_function
import errno
import logging
import optparse
import os
import re
import tempfile
import time
import shutil
import subprocess
import sys
import urlparse
import zipfile

from download_from_google_storage import Gsutil
import gclient_utils
import subcommand

# Analogous to gc.autopacklimit git config.
GC_AUTOPACKLIMIT = 50

GIT_CACHE_CORRUPT_MESSAGE = 'WARNING: The Git cache is corrupt.'

try:
  # pylint: disable=E0602
  WinErr = WindowsError
except NameError:
  class WinErr(Exception):
    pass

class LockError(Exception):
  pass

class RefsHeadsFailedToFetch(Exception):
  pass

class Lockfile(object):
  """Class to represent a cross-platform process-specific lockfile."""

  def __init__(self, path):
    self.path = os.path.abspath(path)
    self.lockfile = self.path + ".lock"
    self.pid = os.getpid()

  def _read_pid(self):
    """Read the pid stored in the lockfile.

    Note: This method is potentially racy. By the time it returns the lockfile
    may have been unlocked, removed, or stolen by some other process.
    """
    try:
      with open(self.lockfile, 'r') as f:
        pid = int(f.readline().strip())
    except (IOError, ValueError):
      pid = None
    return pid

  def _make_lockfile(self):
    """Safely creates a lockfile containing the current pid."""
    open_flags = (os.O_CREAT | os.O_EXCL | os.O_WRONLY)
    fd = os.open(self.lockfile, open_flags, 0o644)
    f = os.fdopen(fd, 'w')
    print(self.pid, file=f)
    f.close()

  def _remove_lockfile(self):
    """Delete the lockfile. Complains (implicitly) if it doesn't exist.

    See gclient_utils.py:rmtree docstring for more explanation on the
    windows case.
    """
    if sys.platform == 'win32':
      lockfile = os.path.normcase(self.lockfile)
      for _ in xrange(3):
        exitcode = subprocess.call(['cmd.exe', '/c',
                                    'del', '/f', '/q', lockfile])
        if exitcode == 0:
          return
        time.sleep(3)
      raise LockError('Failed to remove lock: %s' % lockfile)
    else:
      os.remove(self.lockfile)

  def lock(self):
    """Acquire the lock.

    Note: This is a NON-BLOCKING FAIL-FAST operation.
    Do. Or do not. There is no try.
    """
    try:
      self._make_lockfile()
    except OSError as e:
      if e.errno == errno.EEXIST:
        raise LockError("%s is already locked" % self.path)
      else:
        raise LockError("Failed to create %s (err %s)" % (self.path, e.errno))

  def unlock(self):
    """Release the lock."""
    try:
      if not self.is_locked():
        raise LockError("%s is not locked" % self.path)
      if not self.i_am_locking():
        raise LockError("%s is locked, but not by me" % self.path)
      self._remove_lockfile()
    except WinErr:
      # Windows is unreliable when it comes to file locking.  YMMV.
      pass

  def break_lock(self):
    """Remove the lock, even if it was created by someone else."""
    try:
      self._remove_lockfile()
      return True
    except OSError as exc:
      if exc.errno == errno.ENOENT:
        return False
      else:
        raise

  def is_locked(self):
    """Test if the file is locked by anyone.

    Note: This method is potentially racy. By the time it returns the lockfile
    may have been unlocked, removed, or stolen by some other process.
    """
    return os.path.exists(self.lockfile)

  def i_am_locking(self):
    """Test if the file is locked by this process."""
    return self.is_locked() and self.pid == self._read_pid()


class Mirror(object):

  git_exe = 'git.bat' if sys.platform.startswith('win') else 'git'
  gsutil_exe = os.path.join(
    os.path.dirname(os.path.abspath(__file__)),
    'third_party', 'gsutil', 'gsutil')

  def __init__(self, url, refs=None, print_func=None):
    self.url = url
    self.refs = refs or []
    self.basedir = self.UrlToCacheDir(url)
    self.mirror_path = os.path.join(self.GetCachePath(), self.basedir)
    self.print = print_func or print

  @property
  def bootstrap_bucket(self):
    if 'chrome-internal' in self.url:
      return 'chrome-git-cache'
    else:
      return 'chromium-git-cache'

  @classmethod
  def FromPath(cls, path):
    return cls(cls.CacheDirToUrl(path))

  @staticmethod
  def UrlToCacheDir(url):
    """Convert a git url to a normalized form for the cache dir path."""
    parsed = urlparse.urlparse(url)
    norm_url = parsed.netloc + parsed.path
    if norm_url.endswith('.git'):
      norm_url = norm_url[:-len('.git')]
    return norm_url.replace('-', '--').replace('/', '-').lower()

  @staticmethod
  def CacheDirToUrl(path):
    """Convert a cache dir path to its corresponding url."""
    netpath = re.sub(r'\b-\b', '/', os.path.basename(path)).replace('--', '-')
    return 'https://%s' % netpath

  @staticmethod
  def FindExecutable(executable):
    """This mimics the "which" utility."""
    path_folders = os.environ.get('PATH').split(os.pathsep)

    for path_folder in path_folders:
      target = os.path.join(path_folder, executable)
      # Just incase we have some ~/blah paths.
      target = os.path.abspath(os.path.expanduser(target))
      if os.path.isfile(target) and os.access(target, os.X_OK):
        return target
      if sys.platform.startswith('win'):
        for suffix in ('.bat', '.cmd', '.exe'):
          alt_target = target + suffix
          if os.path.isfile(alt_target) and os.access(alt_target, os.X_OK):
            return alt_target
    return None

  @classmethod
  def SetCachePath(cls, cachepath):
    setattr(cls, 'cachepath', cachepath)

  @classmethod
  def GetCachePath(cls):
    if not hasattr(cls, 'cachepath'):
      try:
        cachepath = subprocess.check_output(
            [cls.git_exe, 'config', '--global', 'cache.cachepath']).strip()
      except subprocess.CalledProcessError:
        cachepath = None
      if not cachepath:
        raise RuntimeError('No global cache.cachepath git configuration found.')
      setattr(cls, 'cachepath', cachepath)
    return getattr(cls, 'cachepath')

  def RunGit(self, cmd, **kwargs):
    """Run git in a subprocess."""
    cwd = kwargs.setdefault('cwd', self.mirror_path)
    kwargs.setdefault('print_stdout', False)
    kwargs.setdefault('filter_fn', self.print)
    env = kwargs.get('env') or kwargs.setdefault('env', os.environ.copy())
    env.setdefault('GIT_ASKPASS', 'true')
    env.setdefault('SSH_ASKPASS', 'true')
    self.print('running "git %s" in "%s"' % (' '.join(cmd), cwd))
    gclient_utils.CheckCallAndFilter([self.git_exe] + cmd, **kwargs)

  def config(self, cwd=None):
    if cwd is None:
      cwd = self.mirror_path

    # Don't run git-gc in a daemon.  Bad things can happen if it gets killed.
    self.RunGit(['config', 'gc.autodetach', '0'], cwd=cwd)

    # Don't combine pack files into one big pack file.  It's really slow for
    # repositories, and there's no way to track progress and make sure it's
    # not stuck.
    self.RunGit(['config', 'gc.autopacklimit', '0'], cwd=cwd)

    # Allocate more RAM for cache-ing delta chains, for better performance
    # of "Resolving deltas".
    self.RunGit(['config', 'core.deltaBaseCacheLimit',
                 gclient_utils.DefaultDeltaBaseCacheLimit()], cwd=cwd)

    self.RunGit(['config', 'remote.origin.url', self.url], cwd=cwd)
    self.RunGit(['config', '--replace-all', 'remote.origin.fetch',
                 '+refs/heads/*:refs/heads/*'], cwd=cwd)
    for ref in self.refs:
      ref = ref.lstrip('+').rstrip('/')
      if ref.startswith('refs/'):
        refspec = '+%s:%s' % (ref, ref)
      else:
        refspec = '+refs/%s/*:refs/%s/*' % (ref, ref)
      self.RunGit(['config', '--add', 'remote.origin.fetch', refspec], cwd=cwd)

  def bootstrap_repo(self, directory):
    """Bootstrap the repo from Google Stroage if possible.

    More apt-ly named bootstrap_repo_from_cloud_if_possible_else_do_nothing().
    """

    python_fallback = False
    if sys.platform.startswith('win') and not self.FindExecutable('7z'):
      python_fallback = True
    elif sys.platform.startswith('darwin'):
      # The OSX version of unzip doesn't support zip64.
      python_fallback = True
    elif not self.FindExecutable('unzip'):
      python_fallback = True

    gs_folder = 'gs://%s/%s' % (self.bootstrap_bucket, self.basedir)
    gsutil = Gsutil(self.gsutil_exe, boto_path=None, bypass_prodaccess=True)
    # Get the most recent version of the zipfile.
    _, ls_out, _ = gsutil.check_call('ls', gs_folder)
    ls_out_sorted = sorted(ls_out.splitlines())
    if not ls_out_sorted:
      # This repo is not on Google Storage.
      return False
    latest_checkout = ls_out_sorted[-1]

    # Download zip file to a temporary directory.
    try:
      tempdir = tempfile.mkdtemp(prefix='_cache_tmp', dir=self.GetCachePath())
      self.print('Downloading %s' % latest_checkout)
      code = gsutil.call('cp', latest_checkout, tempdir)
      if code:
        return False
      filename = os.path.join(tempdir, latest_checkout.split('/')[-1])

      # Unpack the file with 7z on Windows, unzip on linux, or fallback.
      if not python_fallback:
        if sys.platform.startswith('win'):
          cmd = ['7z', 'x', '-o%s' % directory, '-tzip', filename]
        else:
          cmd = ['unzip', filename, '-d', directory]
        retcode = subprocess.call(cmd)
      else:
        try:
          with zipfile.ZipFile(filename, 'r') as f:
            f.printdir()
            f.extractall(directory)
        except Exception as e:
          self.print('Encountered error: %s' % str(e), file=sys.stderr)
          retcode = 1
        else:
          retcode = 0
    finally:
      # Clean up the downloaded zipfile.
      gclient_utils.rmtree(tempdir)

    if retcode:
      self.print(
          'Extracting bootstrap zipfile %s failed.\n'
          'Resuming normal operations.' % filename)
      return False
    return True

  def exists(self):
    return os.path.isfile(os.path.join(self.mirror_path, 'config'))

  def _ensure_bootstrapped(self, depth, bootstrap, force=False):
    tempdir = None
    config_file = os.path.join(self.mirror_path, 'config')
    pack_dir = os.path.join(self.mirror_path, 'objects', 'pack')
    pack_files = []

    if os.path.isdir(pack_dir):
      pack_files = [f for f in os.listdir(pack_dir) if f.endswith('.pack')]

    should_bootstrap = (force or
                        not os.path.exists(config_file) or
                        len(pack_files) > GC_AUTOPACKLIMIT)
    if should_bootstrap:
      tempdir = tempfile.mkdtemp(
          prefix='_cache_tmp', suffix=self.basedir, dir=self.GetCachePath())
      bootstrapped = not depth and bootstrap and self.bootstrap_repo(tempdir)
      if bootstrapped:
        # Bootstrap succeeded; delete previous cache, if any.
        try:
          # Try to move folder to tempdir if possible.
          defunct_dir = tempfile.mkdtemp()
          shutil.move(self.mirror_path, defunct_dir)
          self.print('Moved defunct directory for repository %s from %s to %s'
                     % (self.url, self.mirror_path, defunct_dir))
        except Exception:
          gclient_utils.rmtree(self.mirror_path)
      elif not os.path.exists(config_file):
        # Bootstrap failed, no previous cache; start with a bare git dir.
        self.RunGit(['init', '--bare'], cwd=tempdir)
      else:
        # Bootstrap failed, previous cache exists; warn and continue.
        logging.warn(
            'Git cache has a lot of pack files (%d).  Tried to re-bootstrap '
            'but failed.  Continuing with non-optimized repository.'
            % len(pack_files))
        gclient_utils.rmtree(tempdir)
        tempdir = None
    else:
      if depth and os.path.exists(os.path.join(self.mirror_path, 'shallow')):
        logging.warn(
            'Shallow fetch requested, but repo cache already exists.')
    return tempdir

  def _fetch(self, rundir, verbose, depth):
    self.config(rundir)
    v = []
    d = []
    if verbose:
      v = ['-v', '--progress']
    if depth:
      d = ['--depth', str(depth)]
    fetch_cmd = ['fetch'] + v + d + ['origin']
    fetch_specs = subprocess.check_output(
        [self.git_exe, 'config', '--get-all', 'remote.origin.fetch'],
        cwd=rundir).strip().splitlines()
    for spec in fetch_specs:
      try:
        self.print('Fetching %s' % spec)
        self.RunGit(fetch_cmd + [spec], cwd=rundir, retry=True)
      except subprocess.CalledProcessError:
        if spec == '+refs/heads/*:refs/heads/*':
          raise RefsHeadsFailedToFetch
        logging.warn('Fetch of %s failed' % spec)

  def populate(self, depth=None, shallow=False, bootstrap=False,
               verbose=False, ignore_lock=False):
    assert self.GetCachePath()
    if shallow and not depth:
      depth = 10000
    gclient_utils.safe_makedirs(self.GetCachePath())

    lockfile = Lockfile(self.mirror_path)
    if not ignore_lock:
      lockfile.lock()

    tempdir = None
    try:
      tempdir = self._ensure_bootstrapped(depth, bootstrap)
      rundir = tempdir or self.mirror_path
      self._fetch(rundir, verbose, depth)
    except RefsHeadsFailedToFetch:
      # This is a major failure, we need to clean and force a bootstrap.
      gclient_utils.rmtree(rundir)
      self.print(GIT_CACHE_CORRUPT_MESSAGE)
      tempdir = self._ensure_bootstrapped(depth, bootstrap, force=True)
      assert tempdir
      self._fetch(tempdir or self.mirror_path, verbose, depth)
    finally:
      if tempdir:
        os.rename(tempdir, self.mirror_path)
      if not ignore_lock:
        lockfile.unlock()

  def update_bootstrap(self, prune=False):
    # The files are named <git number>.zip
    gen_number = subprocess.check_output(
        [self.git_exe, 'number', 'master'], cwd=self.mirror_path).strip()
    self.RunGit(['gc'])  # Run Garbage Collect to compress packfile.
    # Creating a temp file and then deleting it ensures we can use this name.
    _, tmp_zipfile = tempfile.mkstemp(suffix='.zip')
    os.remove(tmp_zipfile)
    subprocess.call(['zip', '-r', tmp_zipfile, '.'], cwd=self.mirror_path)
    gsutil = Gsutil(path=self.gsutil_exe, boto_path=None)
    gs_folder = 'gs://%s/%s' % (self.bootstrap_bucket, self.basedir)
    dest_name = '%s/%s.zip' % (gs_folder, gen_number)
    gsutil.call('cp', tmp_zipfile, dest_name)
    os.remove(tmp_zipfile)

    # Remove all other files in the same directory.
    if prune:
      _, ls_out, _ = gsutil.check_call('ls', gs_folder)
      for filename in ls_out.splitlines():
        if filename == dest_name:
          continue
        gsutil.call('rm', filename)

  @staticmethod
  def DeleteTmpPackFiles(path):
    pack_dir = os.path.join(path, 'objects', 'pack')
    if not os.path.isdir(pack_dir):
      return
    pack_files = [f for f in os.listdir(pack_dir) if
                  f.startswith('.tmp-') or f.startswith('tmp_pack_')]
    for f in pack_files:
      f = os.path.join(pack_dir, f)
      try:
        os.remove(f)
        logging.warn('Deleted stale temporary pack file %s' % f)
      except OSError:
        logging.warn('Unable to delete temporary pack file %s' % f)

  @classmethod
  def BreakLocks(cls, path):
    did_unlock = False
    lf = Lockfile(path)
    if lf.break_lock():
      did_unlock = True
    # Look for lock files that might have been left behind by an interrupted
    # git process.
    lf = os.path.join(path, 'config.lock')
    if os.path.exists(lf):
      os.remove(lf)
      did_unlock = True
    cls.DeleteTmpPackFiles(path)
    return did_unlock

  def unlock(self):
    return self.BreakLocks(self.mirror_path)

  @classmethod
  def UnlockAll(cls):
    cachepath = cls.GetCachePath()
    if not cachepath:
      return
    dirlist = os.listdir(cachepath)
    repo_dirs = set([os.path.join(cachepath, path) for path in dirlist
                     if os.path.isdir(os.path.join(cachepath, path))])
    for dirent in dirlist:
      if dirent.startswith('_cache_tmp') or dirent.startswith('tmp'):
        gclient_utils.rmtree(os.path.join(cachepath, dirent))
      elif (dirent.endswith('.lock') and
          os.path.isfile(os.path.join(cachepath, dirent))):
        repo_dirs.add(os.path.join(cachepath, dirent[:-5]))

    unlocked_repos = []
    for repo_dir in repo_dirs:
      if cls.BreakLocks(repo_dir):
        unlocked_repos.append(repo_dir)

    return unlocked_repos

@subcommand.usage('[url of repo to check for caching]')
def CMDexists(parser, args):
  """Check to see if there already is a cache of the given repo."""
  _, args = parser.parse_args(args)
  if not len(args) == 1:
    parser.error('git cache exists only takes exactly one repo url.')
  url = args[0]
  mirror = Mirror(url)
  if mirror.exists():
    print(mirror.mirror_path)
    return 0
  return 1


@subcommand.usage('[url of repo to create a bootstrap zip file]')
def CMDupdate_bootstrap(parser, args):
  """Create and uploads a bootstrap tarball."""
  # Lets just assert we can't do this on Windows.
  if sys.platform.startswith('win'):
    print('Sorry, update bootstrap will not work on Windows.', file=sys.stderr)
    return 1

  parser.add_option('--prune', action='store_true',
                    help='Prune all other cached zipballs of the same repo.')

  # First, we need to ensure the cache is populated.
  populate_args = args[:]
  populate_args.append('--no_bootstrap')
  CMDpopulate(parser, populate_args)

  # Get the repo directory.
  options, args = parser.parse_args(args)
  url = args[0]
  mirror = Mirror(url)
  mirror.update_bootstrap(options.prune)
  return 0


@subcommand.usage('[url of repo to add to or update in cache]')
def CMDpopulate(parser, args):
  """Ensure that the cache has all up-to-date objects for the given repo."""
  parser.add_option('--depth', type='int',
                    help='Only cache DEPTH commits of history')
  parser.add_option('--shallow', '-s', action='store_true',
                    help='Only cache 10000 commits of history')
  parser.add_option('--ref', action='append',
                    help='Specify additional refs to be fetched')
  parser.add_option('--no_bootstrap', action='store_true',
                    help='Don\'t bootstrap from Google Storage')
  parser.add_option('--ignore_locks', action='store_true',
                    help='Don\'t try to lock repository')

  options, args = parser.parse_args(args)
  if not len(args) == 1:
    parser.error('git cache populate only takes exactly one repo url.')
  url = args[0]

  mirror = Mirror(url, refs=options.ref)
  kwargs = {
      'verbose': options.verbose,
      'shallow': options.shallow,
      'bootstrap': not options.no_bootstrap,
      'ignore_lock': options.ignore_locks,
  }
  if options.depth:
    kwargs['depth'] = options.depth
  mirror.populate(**kwargs)


@subcommand.usage('[url of repo to unlock, or -a|--all]')
def CMDunlock(parser, args):
  """Unlock one or all repos if their lock files are still around."""
  parser.add_option('--force', '-f', action='store_true',
                    help='Actually perform the action')
  parser.add_option('--all', '-a', action='store_true',
                    help='Unlock all repository caches')
  options, args = parser.parse_args(args)
  if len(args) > 1 or (len(args) == 0 and not options.all):
    parser.error('git cache unlock takes exactly one repo url, or --all')

  if not options.force:
    cachepath = Mirror.GetCachePath()
    lockfiles = [os.path.join(cachepath, path)
                 for path in os.listdir(cachepath)
                 if path.endswith('.lock') and os.path.isfile(path)]
    parser.error('git cache unlock requires -f|--force to do anything. '
                 'Refusing to unlock the following repo caches: '
                 ', '.join(lockfiles))

  unlocked_repos = []
  if options.all:
    unlocked_repos.extend(Mirror.UnlockAll())
  else:
    m = Mirror(args[0])
    if m.unlock():
      unlocked_repos.append(m.mirror_path)

  if unlocked_repos:
    logging.info('Broke locks on these caches:\n  %s' % '\n  '.join(
        unlocked_repos))


class OptionParser(optparse.OptionParser):
  """Wrapper class for OptionParser to handle global options."""

  def __init__(self, *args, **kwargs):
    optparse.OptionParser.__init__(self, *args, prog='git cache', **kwargs)
    self.add_option('-c', '--cache-dir',
                    help='Path to the directory containing the cache')
    self.add_option('-v', '--verbose', action='count', default=1,
                    help='Increase verbosity (can be passed multiple times)')
    self.add_option('-q', '--quiet', action='store_true',
                    help='Suppress all extraneous output')

  def parse_args(self, args=None, values=None):
    options, args = optparse.OptionParser.parse_args(self, args, values)
    if options.quiet:
      options.verbose = 0

    levels = [logging.ERROR, logging.WARNING, logging.INFO, logging.DEBUG]
    logging.basicConfig(level=levels[min(options.verbose, len(levels) - 1)])

    try:
      global_cache_dir = Mirror.GetCachePath()
    except RuntimeError:
      global_cache_dir = None
    if options.cache_dir:
      if global_cache_dir and (
          os.path.abspath(options.cache_dir) !=
          os.path.abspath(global_cache_dir)):
        logging.warn('Overriding globally-configured cache directory.')
      Mirror.SetCachePath(options.cache_dir)

    return options, args


def main(argv):
  dispatcher = subcommand.CommandDispatcher(__name__)
  return dispatcher.execute(OptionParser(), argv)


if __name__ == '__main__':
  sys.exit(main(sys.argv[1:]))