Revert "Use OS level locking in git_cache.py"
This reverts commit d3affaa62488e0d67e04f810f1c2f2f40793e06b.
Reason for revert: no attribute ignore_lock
Original change's description:
> Use OS level locking in git_cache.py
>
> Without OS level locking it's possible to leave "lock" files on disk
> which will prevent next run to acquire those locks. This can easily
> happen if SIGKIL is issued.
>
> R=apolito@google.com, ehmaldonado@chromium.org
>
> Bug: 1049610
> Change-Id: Id87aa1376b9ea5ff0c2d14f3603636493ed1dd5b
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2189333
> Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
> Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
> Commit-Queue: Josip Sokcevic <sokcevic@google.com>
TBR=iannucci@chromium.org,ehmaldonado@chromium.org,apolito@google.com,infra-scoped@luci-project-accounts.iam.gserviceaccount.com,sokcevic@google.com
Change-Id: Iecc963e0a99d7f59f3f8801e529839346f9fbaf3
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1049610
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2211186
Reviewed-by: Josip Sokcevic <sokcevic@google.com>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>
diff --git a/git_cache.py b/git_cache.py
index 8580be7..0ca9c7d 100755
--- a/git_cache.py
+++ b/git_cache.py
@@ -26,7 +26,6 @@
from download_from_google_storage import Gsutil
import gclient_utils
-import lockfile
import subcommand
# Analogous to gc.autopacklimit git config.
@@ -41,6 +40,9 @@
class WinErr(Exception):
pass
+class LockError(Exception):
+ pass
+
class ClobberNeeded(Exception):
pass
@@ -80,6 +82,116 @@
sleep_time *= 2
+class Lockfile(object):
+ """Class to represent a cross-platform process-specific lockfile."""
+
+ def __init__(self, path, timeout=0):
+ self.path = os.path.abspath(path)
+ self.timeout = timeout
+ 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)
+
+ def delete():
+ exitcode = subprocess.call(['cmd.exe', '/c',
+ 'del', '/f', '/q', lockfile])
+ if exitcode != 0:
+ raise LockError('Failed to remove lock: %s' % (lockfile,))
+ exponential_backoff_retry(
+ delete,
+ excs=(LockError,),
+ name='del [%s]' % (lockfile,))
+ else:
+ os.remove(self.lockfile)
+
+ def lock(self):
+ """Acquire the lock.
+
+ This will block with a deadline of self.timeout seconds.
+ """
+ elapsed = 0
+ while True:
+ try:
+ self._make_lockfile()
+ return
+ except OSError as e:
+ if elapsed < self.timeout:
+ sleep_time = max(10, min(3, self.timeout - elapsed))
+ logging.info('Could not create git cache lockfile; '
+ 'will retry after sleep(%d).', sleep_time);
+ elapsed += sleep_time
+ time.sleep(sleep_time)
+ continue
+ 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'
@@ -456,6 +568,7 @@
shallow=False,
bootstrap=False,
verbose=False,
+ ignore_lock=False,
lock_timeout=0,
reset_fetch_config=False):
assert self.GetCachePath()
@@ -463,21 +576,25 @@
depth = 10000
gclient_utils.safe_makedirs(self.GetCachePath())
- with lockfile.lock(self.mirror_path, lock_timeout):
- try:
- self._ensure_bootstrapped(depth, bootstrap, reset_fetch_config)
- self._fetch(self.mirror_path, verbose, depth, no_fetch_tags,
- reset_fetch_config)
- except ClobberNeeded:
- # This is a major failure, we need to clean and force a bootstrap.
- gclient_utils.rmtree(self.mirror_path)
- self.print(GIT_CACHE_CORRUPT_MESSAGE)
- self._ensure_bootstrapped(depth,
- bootstrap,
- reset_fetch_config,
- force=True)
- self._fetch(self.mirror_path, verbose, depth, no_fetch_tags,
- reset_fetch_config)
+ lockfile = Lockfile(self.mirror_path, lock_timeout)
+ if not ignore_lock:
+ lockfile.lock()
+
+ try:
+ self._ensure_bootstrapped(depth, bootstrap, reset_fetch_config)
+ self._fetch(self.mirror_path, verbose, depth, no_fetch_tags,
+ reset_fetch_config)
+ except ClobberNeeded:
+ # This is a major failure, we need to clean and force a bootstrap.
+ gclient_utils.rmtree(self.mirror_path)
+ self.print(GIT_CACHE_CORRUPT_MESSAGE)
+ self._ensure_bootstrapped(
+ depth, bootstrap, reset_fetch_config, force=True)
+ self._fetch(self.mirror_path, verbose, depth, no_fetch_tags,
+ reset_fetch_config)
+ finally:
+ if not ignore_lock:
+ lockfile.unlock()
def update_bootstrap(self, prune=False, gc_aggressive=False):
# The folder is <git number>
@@ -548,6 +665,45 @@
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.rm_file_or_tree(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):
@@ -612,10 +768,9 @@
parser.add_option('--no_bootstrap', '--no-bootstrap',
action='store_true',
help='Don\'t bootstrap from Google Storage')
- parser.add_option('--ignore_locks',
- '--ignore-locks',
+ parser.add_option('--ignore_locks', '--ignore-locks',
action='store_true',
- help='NOOP. This flag will be removed in the future.')
+ help='Don\'t try to lock repository')
parser.add_option('--break-locks',
action='store_true',
help='Break any existing lock instead of just ignoring it')
@@ -625,16 +780,17 @@
options, args = parser.parse_args(args)
if not len(args) == 1:
parser.error('git cache populate only takes exactly one repo url.')
- if options.ignore_lock:
- print('ignore_lock is no longer used. Please remove its usage.')
url = args[0]
mirror = Mirror(url, refs=options.ref)
+ if options.break_locks:
+ mirror.unlock()
kwargs = {
'no_fetch_tags': options.no_fetch_tags,
'verbose': options.verbose,
'shallow': options.shallow,
'bootstrap': not options.no_bootstrap,
+ 'ignore_lock': options.ignore_locks,
'lock_timeout': options.timeout,
'reset_fetch_config': options.reset_fetch_config,
}
@@ -708,10 +864,37 @@
return 0
-@subcommand.usage('do not use - it is a noop.')
+@subcommand.usage('[url of repo to unlock, or -a|--all]')
def CMDunlock(parser, args):
- """This command does nothing."""
- print('This command does nothing and will be removed in the future.')
+ """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):