Mercurial > hg
view tests/test-util.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 | 2372284d9457 |
children | 5aafc3c5bdec |
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# unit tests for mercuril.util utilities from __future__ import absolute_import import contextlib import itertools import unittest from mercurial import pycompat, util, utils @contextlib.contextmanager def mocktimer(incr=0.1, *additional_targets): """Replaces util.timer and additional_targets with a mock The timer starts at 0. On each call the time incremented by the value of incr. If incr is an iterable, then the time is incremented by the next value from that iterable, looping in a cycle when reaching the end. additional_targets must be a sequence of (object, attribute_name) tuples; the mock is set with setattr(object, attribute_name, mock). """ time = [0] try: incr = itertools.cycle(incr) except TypeError: incr = itertools.repeat(incr) def timer(): time[0] += next(incr) return time[0] # record original values orig = util.timer additional_origs = [(o, a, getattr(o, a)) for o, a in additional_targets] # mock out targets util.timer = timer for obj, attr in additional_targets: setattr(obj, attr, timer) try: yield finally: # restore originals util.timer = orig for args in additional_origs: setattr(*args) # attr.s default factory for util.timedstats.start binds the timer we # need to mock out. _start_default = (util.timedcmstats.start.default, 'factory') @contextlib.contextmanager def capturestderr(): """Replace utils.procutil.stderr with a pycompat.bytesio instance The instance is made available as the return value of __enter__. This contextmanager is reentrant. """ orig = utils.procutil.stderr utils.procutil.stderr = pycompat.bytesio() try: yield utils.procutil.stderr finally: utils.procutil.stderr = orig class timedtests(unittest.TestCase): def testtimedcmstatsstr(self): stats = util.timedcmstats() self.assertEqual(str(stats), '<unknown>') self.assertEqual(bytes(stats), b'<unknown>') stats.elapsed = 12.34 self.assertEqual(str(stats), pycompat.sysstr(util.timecount(12.34))) self.assertEqual(bytes(stats), util.timecount(12.34)) def testtimedcmcleanexit(self): # timestamps 1, 4, elapsed time of 4 - 1 = 3 with mocktimer([1, 3], _start_default): with util.timedcm('pass') as stats: # actual context doesn't matter pass self.assertEqual(stats.start, 1) self.assertEqual(stats.elapsed, 3) self.assertEqual(stats.level, 1) def testtimedcmnested(self): # timestamps 1, 3, 6, 10, elapsed times of 6 - 3 = 3 and 10 - 1 = 9 with mocktimer([1, 2, 3, 4], _start_default): with util.timedcm('outer') as outer_stats: with util.timedcm('inner') as inner_stats: # actual context doesn't matter pass self.assertEqual(outer_stats.start, 1) self.assertEqual(outer_stats.elapsed, 9) self.assertEqual(outer_stats.level, 1) self.assertEqual(inner_stats.start, 3) self.assertEqual(inner_stats.elapsed, 3) self.assertEqual(inner_stats.level, 2) def testtimedcmexception(self): # timestamps 1, 4, elapsed time of 4 - 1 = 3 with mocktimer([1, 3], _start_default): try: with util.timedcm('exceptional') as stats: raise ValueError() except ValueError: pass self.assertEqual(stats.start, 1) self.assertEqual(stats.elapsed, 3) self.assertEqual(stats.level, 1) def testtimeddecorator(self): @util.timed def testfunc(callcount=1): callcount -= 1 if callcount: testfunc(callcount) # timestamps 1, 2, 3, 4, elapsed time of 3 - 2 = 1 and 4 - 1 = 3 with mocktimer(1, _start_default): with capturestderr() as out: testfunc(2) self.assertEqual( out.getvalue(), (b' testfunc: 1.000 s\n' b' testfunc: 3.000 s\n'), ) if __name__ == '__main__': import silenttestrunner silenttestrunner.main(__name__)