filelog: wrap revlog instead of inheriting it (API)
The revlog base class exposes a ton of methods. Inheriting the
revlog class for filelog will make it difficult to expose a
clean interface. There will be abstraction violations.
This commit breaks the inheritance of revlog by the filelog
class. Filelog instances now contain a reference to a revlog
instance. Various properties and methods are now proxied to
that instance.
There is precedence for doing this: manifestlog does something
similar. Although, manifestlog has a cleaner interface than
filelog. We'll get there with filelog...
The new filelog class exposes a handful of extra properties and
methods that aren't part of the declared filelog interface.
Every extra item was added in order to get a test to pass. The
set of tests that failed without these extra proxies has
significant overlap with the set of tests that don't work with
the simple store repo. There should be no surprise there.
Hopefully the hardest part about this commit to review are the
changes to bundlerepo and unionrepo. Both repository types
define a custom revlog or revlog-like class and then have a
custom filelog that inherits from both filelog and their custom
revlog. This code has been changed so the filelog types don't
inherit from revlog. Instead, they replace the revlog instance
on the created filelog. This is super hacky. I plan to fix this
in a future commit by parameterizing filelog.__init__.
Because Python function call overhead is a thing, this change
could impact performance by introducing a nearly empty proxy
function for various methods and properties. I would gladly
measure the performance impact of it, but I'm not sure what
operations have tight loops over filelog attribute lookups
or function calls. I know some of the DAG traversal code can
be sensitive about the performance of e.g. parentrevs(). However,
many of these functions are implemented on the revlog class and
therefore have direct access to self.parentrevs() and aren't
going through a proxy.
.. api::
filelog.filelog is now a standalone class and doesn't inherit
from revlog. Instead, it wraps a revlog instance at self._revlog.
This change was made in an attempt to formalize storage APIs and
prevent revlog implementation details leaking through to callers.
Differential Revision: https://phab.mercurial-scm.org/D3154
# lock.py - simple advisory locking scheme for mercurial
#
# 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 __future__ import absolute_import
import contextlib
import errno
import os
import signal
import socket
import time
import warnings
from .i18n import _
from . import (
encoding,
error,
pycompat,
)
from .utils import (
procutil,
)
def _getlockprefix():
"""Return a string which is used to differentiate pid namespaces
It's useful to detect "dead" processes and remove stale locks with
confidence. Typically it's just hostname. On modern linux, we include an
extra Linux-specific pid namespace identifier.
"""
result = encoding.strtolocal(socket.gethostname())
if pycompat.sysplatform.startswith('linux'):
try:
result += '/%x' % os.stat('/proc/self/ns/pid').st_ino
except OSError as ex:
if ex.errno not in (errno.ENOENT, errno.EACCES, errno.ENOTDIR):
raise
return result
@contextlib.contextmanager
def _delayedinterrupt():
"""Block signal interrupt while doing something critical
This makes sure that the code block wrapped by this context manager won't
be interrupted.
For Windows developers: It appears not possible to guard time.sleep()
from CTRL_C_EVENT, so please don't use time.sleep() to test if this is
working.
"""
assertedsigs = []
blocked = False
orighandlers = {}
def raiseinterrupt(num):
if (num == getattr(signal, 'SIGINT', None) or
num == getattr(signal, 'CTRL_C_EVENT', None)):
raise KeyboardInterrupt
else:
raise error.SignalInterrupt
def catchterm(num, frame):
if blocked:
assertedsigs.append(num)
else:
raiseinterrupt(num)
try:
# save handlers first so they can be restored even if a setup is
# interrupted between signal.signal() and orighandlers[] =.
for name in ['CTRL_C_EVENT', 'SIGINT', 'SIGBREAK', 'SIGHUP', 'SIGTERM']:
num = getattr(signal, name, None)
if num and num not in orighandlers:
orighandlers[num] = signal.getsignal(num)
try:
for num in orighandlers:
signal.signal(num, catchterm)
except ValueError:
pass # in a thread? no luck
blocked = True
yield
finally:
# no simple way to reliably restore all signal handlers because
# any loops, recursive function calls, except blocks, etc. can be
# interrupted. so instead, make catchterm() raise interrupt.
blocked = False
try:
for num, handler in orighandlers.items():
signal.signal(num, handler)
except ValueError:
pass # in a thread?
# re-raise interrupt exception if any, which may be shadowed by a new
# interrupt occurred while re-raising the first one
if assertedsigs:
raiseinterrupt(assertedsigs[0])
def trylock(ui, vfs, lockname, timeout, warntimeout, *args, **kwargs):
"""return an acquired lock or raise an a LockHeld exception
This function is responsible to issue warnings and or debug messages about
the held lock while trying to acquires it."""
def printwarning(printer, locker):
"""issue the usual "waiting on lock" message through any channel"""
# show more details for new-style locks
if ':' in locker:
host, pid = locker.split(":", 1)
msg = (_("waiting for lock on %s held by process %r on host %r\n")
% (pycompat.bytestr(l.desc), pycompat.bytestr(pid),
pycompat.bytestr(host)))
else:
msg = (_("waiting for lock on %s held by %r\n")
% (l.desc, pycompat.bytestr(locker)))
printer(msg)
l = lock(vfs, lockname, 0, *args, dolock=False, **kwargs)
debugidx = 0 if (warntimeout and timeout) else -1
warningidx = 0
if not timeout:
warningidx = -1
elif warntimeout:
warningidx = warntimeout
delay = 0
while True:
try:
l._trylock()
break
except error.LockHeld as inst:
if delay == debugidx:
printwarning(ui.debug, inst.locker)
if delay == warningidx:
printwarning(ui.warn, inst.locker)
if timeout <= delay:
raise error.LockHeld(errno.ETIMEDOUT, inst.filename,
l.desc, inst.locker)
time.sleep(1)
delay += 1
l.delay = delay
if l.delay:
if 0 <= warningidx <= l.delay:
ui.warn(_("got lock after %d seconds\n") % l.delay)
else:
ui.debug("got lock after %d seconds\n" % l.delay)
if l.acquirefn:
l.acquirefn()
return l
class lock(object):
'''An advisory lock held by one process to control access to a set
of files. Non-cooperating processes or incorrectly written scripts
can ignore Mercurial's locking scheme and stomp all over the
repository, so don't do that.
Typically used via localrepository.lock() to lock the repository
store (.hg/store/) or localrepository.wlock() to lock everything
else under .hg/.'''
# lock is symlink on platforms that support it, file on others.
# symlink is used because create of directory entry and contents
# are atomic even over nfs.
# old-style lock: symlink to pid
# new-style lock: symlink to hostname:pid
_host = None
def __init__(self, vfs, file, timeout=-1, releasefn=None, acquirefn=None,
desc=None, inheritchecker=None, parentlock=None,
dolock=True):
self.vfs = vfs
self.f = file
self.held = 0
self.timeout = timeout
self.releasefn = releasefn
self.acquirefn = acquirefn
self.desc = desc
self._inheritchecker = inheritchecker
self.parentlock = parentlock
self._parentheld = False
self._inherited = False
self.postrelease = []
self.pid = self._getpid()
if dolock:
self.delay = self.lock()
if self.acquirefn:
self.acquirefn()
def __enter__(self):
return self
def __exit__(self, exc_type, exc_value, exc_tb):
self.release()
def __del__(self):
if self.held:
warnings.warn("use lock.release instead of del lock",
category=DeprecationWarning,
stacklevel=2)
# ensure the lock will be removed
# even if recursive locking did occur
self.held = 1
self.release()
def _getpid(self):
# wrapper around procutil.getpid() to make testing easier
return procutil.getpid()
def lock(self):
timeout = self.timeout
while True:
try:
self._trylock()
return self.timeout - timeout
except error.LockHeld as inst:
if timeout != 0:
time.sleep(1)
if timeout > 0:
timeout -= 1
continue
raise error.LockHeld(errno.ETIMEDOUT, inst.filename, self.desc,
inst.locker)
def _trylock(self):
if self.held:
self.held += 1
return
if lock._host is None:
lock._host = _getlockprefix()
lockname = '%s:%d' % (lock._host, self.pid)
retry = 5
while not self.held and retry:
retry -= 1
try:
with _delayedinterrupt():
self.vfs.makelock(lockname, self.f)
self.held = 1
except (OSError, IOError) as why:
if why.errno == errno.EEXIST:
locker = self._readlock()
if locker is None:
continue
# special case where a parent process holds the lock -- this
# is different from the pid being different because we do
# want the unlock and postrelease functions to be called,
# but the lockfile to not be removed.
if locker == self.parentlock:
self._parentheld = True
self.held = 1
return
locker = self._testlock(locker)
if locker is not None:
raise error.LockHeld(errno.EAGAIN,
self.vfs.join(self.f), self.desc,
locker)
else:
raise error.LockUnavailable(why.errno, why.strerror,
why.filename, self.desc)
if not self.held:
# use empty locker to mean "busy for frequent lock/unlock
# by many processes"
raise error.LockHeld(errno.EAGAIN,
self.vfs.join(self.f), self.desc, "")
def _readlock(self):
"""read lock and return its value
Returns None if no lock exists, pid for old-style locks, and host:pid
for new-style locks.
"""
try:
return self.vfs.readlock(self.f)
except (OSError, IOError) as why:
if why.errno == errno.ENOENT:
return None
raise
def _testlock(self, locker):
if locker is None:
return None
try:
host, pid = locker.split(":", 1)
except ValueError:
return locker
if host != lock._host:
return locker
try:
pid = int(pid)
except ValueError:
return locker
if procutil.testpid(pid):
return locker
# if locker dead, break lock. must do this with another lock
# held, or can race and break valid lock.
try:
l = lock(self.vfs, self.f + '.break', timeout=0)
self.vfs.unlink(self.f)
l.release()
except error.LockError:
return locker
def testlock(self):
"""return id of locker if lock is valid, else None.
If old-style lock, we cannot tell what machine locker is on.
with new-style lock, if locker is on this machine, we can
see if locker is alive. If locker is on this machine but
not alive, we can safely break lock.
The lock file is only deleted when None is returned.
"""
locker = self._readlock()
return self._testlock(locker)
@contextlib.contextmanager
def inherit(self):
"""context for the lock to be inherited by a Mercurial subprocess.
Yields a string that will be recognized by the lock in the subprocess.
Communicating this string to the subprocess needs to be done separately
-- typically by an environment variable.
"""
if not self.held:
raise error.LockInheritanceContractViolation(
'inherit can only be called while lock is held')
if self._inherited:
raise error.LockInheritanceContractViolation(
'inherit cannot be called while lock is already inherited')
if self._inheritchecker is not None:
self._inheritchecker()
if self.releasefn:
self.releasefn()
if self._parentheld:
lockname = self.parentlock
else:
lockname = '%s:%s' % (lock._host, self.pid)
self._inherited = True
try:
yield lockname
finally:
if self.acquirefn:
self.acquirefn()
self._inherited = False
def release(self):
"""release the lock and execute callback function if any
If the lock has been acquired multiple times, the actual release is
delayed to the last release call."""
if self.held > 1:
self.held -= 1
elif self.held == 1:
self.held = 0
if self._getpid() != self.pid:
# we forked, and are not the parent
return
try:
if self.releasefn:
self.releasefn()
finally:
if not self._parentheld:
try:
self.vfs.unlink(self.f)
except OSError:
pass
# The postrelease functions typically assume the lock is not held
# at all.
if not self._parentheld:
for callback in self.postrelease:
callback()
# Prevent double usage and help clear cycles.
self.postrelease = None
def release(*locks):
for lock in locks:
if lock is not None:
lock.release()