Mercurial > hg
view tests/killdaemons.py @ 46607:e9901d01d135
revlog: add a mechanism to verify expected file position before appending
If someone uses `hg debuglocks`, or some non-hg process writes to the .hg
directory without respecting the locks, or if the repo's on a networked
filesystem, it's possible for the revlog code to write out corrupted data.
The form of this corruption can vary depending on what data was written and how
that happened. We are in the "networked filesystem" case (though I've had users
also do this to themselves with the "`hg debuglocks`" scenario), and most often
see this with the changelog. What ends up happening is we produce two items
(let's call them rev1 and rev2) in the .i file that have the same linkrev,
baserev, and offset into the .d file, while the data in the .d file is appended
properly. rev2's compressed_size is accurate for rev2, but when we go to
decompress the data in the .d file, we use the offset that's recorded in the
index file, which is the same as rev1, and attempt to decompress
rev2.compressed_size bytes of rev1's data. This usually does not succeed. :)
When using inline data, this also fails, though I haven't investigated why too
closely. This shows up as a "patch decode" error. I believe what's happening
there is that we're basically ignoring the offset field, getting the data
properly, but since baserev != rev, it thinks this is a delta based on rev
(instead of a full text) and can't actually apply it as such.
For now, I'm going to make this an optional component and default it to entirely
off. I may increase the default severity of this in the future, once I've
enabled it for my users and we gain more experience with it. Luckily, most of my
users have a versioned filesystem and can roll back to before the corruption has
been written, it's just a hassle to do so and not everyone knows how (so it's a
support burden). Users on other filesystems will not have that luxury, and this
can cause them to have a corrupted repository that they are unlikely to know how
to resolve, and they'll see this as a data-loss event. Refusing to create the
corruption is a much better user experience.
This mechanism is not perfect. There may be false-negatives (racy writes that
are not detected). There should not be any false-positives (non-racy writes that
are detected as such). This is not a mechanism that makes putting a repo on a
networked filesystem "safe" or "supported", just *less* likely to cause
corruption.
Differential Revision: https://phab.mercurial-scm.org/D9952
author | Kyle Lippincott <spectral@google.com> |
---|---|
date | Wed, 03 Feb 2021 16:33:10 -0800 |
parents | c102b704edb5 |
children | 6000f5b25c9b |
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#!/usr/bin/env python3 from __future__ import absolute_import import errno import os import signal import sys import time if os.name == 'nt': import ctypes _BOOL = ctypes.c_long _DWORD = ctypes.c_ulong _UINT = ctypes.c_uint _HANDLE = ctypes.c_void_p ctypes.windll.kernel32.CloseHandle.argtypes = [_HANDLE] ctypes.windll.kernel32.CloseHandle.restype = _BOOL ctypes.windll.kernel32.GetLastError.argtypes = [] ctypes.windll.kernel32.GetLastError.restype = _DWORD ctypes.windll.kernel32.OpenProcess.argtypes = [_DWORD, _BOOL, _DWORD] ctypes.windll.kernel32.OpenProcess.restype = _HANDLE ctypes.windll.kernel32.TerminateProcess.argtypes = [_HANDLE, _UINT] ctypes.windll.kernel32.TerminateProcess.restype = _BOOL ctypes.windll.kernel32.WaitForSingleObject.argtypes = [_HANDLE, _DWORD] ctypes.windll.kernel32.WaitForSingleObject.restype = _DWORD def _check(ret, expectederr=None): if ret == 0: winerrno = ctypes.GetLastError() if winerrno == expectederr: return True raise ctypes.WinError(winerrno) def kill(pid, logfn, tryhard=True): logfn('# Killing daemon process %d' % pid) PROCESS_TERMINATE = 1 PROCESS_QUERY_INFORMATION = 0x400 SYNCHRONIZE = 0x00100000 WAIT_OBJECT_0 = 0 WAIT_TIMEOUT = 258 WAIT_FAILED = _DWORD(0xFFFFFFFF).value handle = ctypes.windll.kernel32.OpenProcess( PROCESS_TERMINATE | SYNCHRONIZE | PROCESS_QUERY_INFORMATION, False, pid, ) if handle is None: _check(0, 87) # err 87 when process not found return # process not found, already finished try: r = ctypes.windll.kernel32.WaitForSingleObject(handle, 100) if r == WAIT_OBJECT_0: pass # terminated, but process handle still available elif r == WAIT_TIMEOUT: _check(ctypes.windll.kernel32.TerminateProcess(handle, -1)) elif r == WAIT_FAILED: _check(0) # err stored in GetLastError() # TODO?: forcefully kill when timeout # and ?shorter waiting time? when tryhard==True r = ctypes.windll.kernel32.WaitForSingleObject(handle, 100) # timeout = 100 ms if r == WAIT_OBJECT_0: pass # process is terminated elif r == WAIT_TIMEOUT: logfn('# Daemon process %d is stuck') elif r == WAIT_FAILED: _check(0) # err stored in GetLastError() except: # re-raises ctypes.windll.kernel32.CloseHandle(handle) # no _check, keep error raise _check(ctypes.windll.kernel32.CloseHandle(handle)) else: def kill(pid, logfn, tryhard=True): try: os.kill(pid, 0) logfn('# Killing daemon process %d' % pid) os.kill(pid, signal.SIGTERM) if tryhard: for i in range(10): time.sleep(0.05) os.kill(pid, 0) else: time.sleep(0.1) os.kill(pid, 0) logfn('# Daemon process %d is stuck - really killing it' % pid) os.kill(pid, signal.SIGKILL) except OSError as err: if err.errno != errno.ESRCH: raise def killdaemons(pidfile, tryhard=True, remove=False, logfn=None): if not logfn: logfn = lambda s: s # Kill off any leftover daemon processes try: pids = [] with open(pidfile) as fp: for line in fp: try: pid = int(line) if pid <= 0: raise ValueError except ValueError: logfn( '# Not killing daemon process %s - invalid pid' % line.rstrip() ) continue pids.append(pid) for pid in pids: kill(pid, logfn, tryhard) if remove: os.unlink(pidfile) except IOError: pass if __name__ == '__main__': if len(sys.argv) > 1: (path,) = sys.argv[1:] else: path = os.environ["DAEMON_PIDS"] killdaemons(path, remove=True)