view tests/test-lock.py @ 42222:57203e0210f8

copies: calculate mergecopies() based on pathcopies()

When copies are stored in changesets, we need a changeset-centric
version of mergecopies() just like we have a changeset-centric version
of pathcopies(). I think the natural way of thinking about
mergecopies() is in terms of pathcopies() from the base to each of the
commits. So if we can rewrite mergecopies() based on two such
pathcopies() calls, we'll get the changeset-centric version for
free. That's what this patch does.

A nice bonus is that it ends up being a lot simpler. mergecopies() has
accumulated a lot of technical debt over time. One good example is the
code for dealing with grafts (the "partial/incomplete/dirty"
stuff). Since pathcopies() already deals with backwards renames and
ping-pong renames, we get that for free.

I've run tests with hard-coded debug logging for "fullcopy" and while
I haven't looked at every difference it produces, all the ones I have
looked at seemed reasonable to me. I'm a little surprised that no more
tests fail when run with '--extra-config-opt
experimental.copies.read-from=compatibility' compared to before this
patch. This patch also fixes the broken cases in test-annotate.t and
test-fastannotate.t. It also enables the part of test-copies.t that
was previously disabled exactly because mergecopies() needed to get a
changeset-centric version.

One drawback of the rewritten code is that we may now make
remotefilelog prefetch more files. We used to prefetch files that were
unique to either side of the merge compared to the other. We now
prefetch files that are unique to either side of the merge compared to
the base. This means that if you added the same file to each side, we
would not prefetch it before, but we would now. Such cases are
probably quite rare, but one likely scenario where they happen is when
moving from a commit to its successor (or the other way around). The
user will probably already have the files in the cache in such cases,
so it's probably not a big deal.

Some timings for calculating mergecopies between two revisions
(revisions shown on each line, all using the common ancestor as base):

In the hg repo:
4.8 4.9: 0.21s -> 0.21s
4.0 4.8: 0.35s -> 0.63s

In and old copy of the mozilla-unified repo:
FIREFOX_BETA_60_BASE^ FIREFOX_BETA_60_BASE: 0.82s -> 0.82s
FIREFOX_NIGHTLY_59_END FIREFOX_BETA_60_BASE: 2.5s -> 2.6s
FIREFOX_BETA_59_END FIREFOX_BETA_60_BASE: 3.9s -> 4.1s
FIREFOX_AURORA_50_BASE FIREFOX_BETA_60_BASE: 31s -> 33s

So it's measurably slower in most cases. The most significant
difference is in the hg repo between revisions 4.0 and 4.8. In that
case it seems to come from the fact that pathcopies() uses
fctx.isintroducedafter() (in _tracefile), while the old mergecopies()
used fctx.linkrev() (in _checkcopies()). That results in a single call
to filectx._adjustlinkrev(), which is responsible for the entire
difference in time (in my repo). So we pay a performance penalty but
we get more correct code (see change in
test-mv-cp-st-diff.t). Deleting the "== f.filenode()" in _tracefile()
recovers the lost performance in the hg repo.

There were are few other optimizations in _checkcopies() that I could
not measure any impact from. One was from the "seen" set. Another was
from a "continue" when the file was not in the destination manifest
(corresponding to "am" in _tracefile).

Also note that merge copies are not calculated when updating with a
clean working copy, which is probably the most common case. I
therefore think the much simpler code is worth the slowdown.

Differential Revision: https://phab.mercurial-scm.org/D6255

from __future__ import absolute_import

import copy
import errno
import tempfile
import types
import unittest

import silenttestrunner

from mercurial import (
    encoding,
    error,
    lock,
    vfs as vfsmod,
)

testlockname = b'testlock'

# work around http://bugs.python.org/issue1515
if types.MethodType not in copy._deepcopy_dispatch:
    def _deepcopy_method(x, memo):
        return type(x)(x.__func__, copy.deepcopy(x.__self__, memo), x.im_class)
    copy._deepcopy_dispatch[types.MethodType] = _deepcopy_method

class lockwrapper(lock.lock):
    def __init__(self, pidoffset, *args, **kwargs):
        # lock.lock.__init__() calls lock(), so the pidoffset assignment needs
        # to be earlier
        self._pidoffset = pidoffset
        super(lockwrapper, self).__init__(*args, **kwargs)
    def _getpid(self):
        return super(lockwrapper, self)._getpid() + self._pidoffset

class teststate(object):
    def __init__(self, testcase, dir, pidoffset=0):
        self._testcase = testcase
        self._acquirecalled = False
        self._releasecalled = False
        self._postreleasecalled = False
        self.vfs = vfsmod.vfs(dir, audit=False)
        self._pidoffset = pidoffset

    def makelock(self, *args, **kwargs):
        l = lockwrapper(self._pidoffset, self.vfs, testlockname,
                        releasefn=self.releasefn, acquirefn=self.acquirefn,
                        *args, **kwargs)
        l.postrelease.append(self.postreleasefn)
        return l

    def acquirefn(self):
        self._acquirecalled = True

    def releasefn(self):
        self._releasecalled = True

    def postreleasefn(self):
        self._postreleasecalled = True

    def assertacquirecalled(self, called):
        self._testcase.assertEqual(
            self._acquirecalled, called,
            'expected acquire to be %s but was actually %s' % (
                self._tocalled(called),
                self._tocalled(self._acquirecalled),
            ))

    def resetacquirefn(self):
        self._acquirecalled = False

    def assertreleasecalled(self, called):
        self._testcase.assertEqual(
            self._releasecalled, called,
            'expected release to be %s but was actually %s' % (
                self._tocalled(called),
                self._tocalled(self._releasecalled),
            ))

    def assertpostreleasecalled(self, called):
        self._testcase.assertEqual(
            self._postreleasecalled, called,
            'expected postrelease to be %s but was actually %s' % (
                self._tocalled(called),
                self._tocalled(self._postreleasecalled),
            ))

    def assertlockexists(self, exists):
        actual = self.vfs.lexists(testlockname)
        self._testcase.assertEqual(
            actual, exists,
            'expected lock to %s but actually did %s' % (
                self._toexists(exists),
                self._toexists(actual),
            ))

    def _tocalled(self, called):
        if called:
            return 'called'
        else:
            return 'not called'

    def _toexists(self, exists):
        if exists:
            return 'exist'
        else:
            return 'not exist'

class testlock(unittest.TestCase):
    def testlock(self):
        state = teststate(self, tempfile.mkdtemp(dir=encoding.getcwd()))
        lock = state.makelock()
        state.assertacquirecalled(True)
        lock.release()
        state.assertreleasecalled(True)
        state.assertpostreleasecalled(True)
        state.assertlockexists(False)

    def testrecursivelock(self):
        state = teststate(self, tempfile.mkdtemp(dir=encoding.getcwd()))
        lock = state.makelock()
        state.assertacquirecalled(True)

        state.resetacquirefn()
        lock.lock()
        # recursive lock should not call acquirefn again
        state.assertacquirecalled(False)

        lock.release() # brings lock refcount down from 2 to 1
        state.assertreleasecalled(False)
        state.assertpostreleasecalled(False)
        state.assertlockexists(True)

        lock.release() # releases the lock
        state.assertreleasecalled(True)
        state.assertpostreleasecalled(True)
        state.assertlockexists(False)

    def testlockfork(self):
        state = teststate(self, tempfile.mkdtemp(dir=encoding.getcwd()))
        lock = state.makelock()
        state.assertacquirecalled(True)

        # fake a fork
        forklock = copy.copy(lock)
        forklock._pidoffset = 1
        forklock.release()
        state.assertreleasecalled(False)
        state.assertpostreleasecalled(False)
        state.assertlockexists(True)

        # release the actual lock
        lock.release()
        state.assertreleasecalled(True)
        state.assertpostreleasecalled(True)
        state.assertlockexists(False)

    def testinheritlock(self):
        d = tempfile.mkdtemp(dir=encoding.getcwd())
        parentstate = teststate(self, d)
        parentlock = parentstate.makelock()
        parentstate.assertacquirecalled(True)

        # set up lock inheritance
        with parentlock.inherit() as lockname:
            parentstate.assertreleasecalled(True)
            parentstate.assertpostreleasecalled(False)
            parentstate.assertlockexists(True)

            childstate = teststate(self, d, pidoffset=1)
            childlock = childstate.makelock(parentlock=lockname)
            childstate.assertacquirecalled(True)

            childlock.release()
            childstate.assertreleasecalled(True)
            childstate.assertpostreleasecalled(False)
            childstate.assertlockexists(True)

            parentstate.resetacquirefn()

        parentstate.assertacquirecalled(True)

        parentlock.release()
        parentstate.assertreleasecalled(True)
        parentstate.assertpostreleasecalled(True)
        parentstate.assertlockexists(False)

    def testmultilock(self):
        d = tempfile.mkdtemp(dir=encoding.getcwd())
        state0 = teststate(self, d)
        lock0 = state0.makelock()
        state0.assertacquirecalled(True)

        with lock0.inherit() as lock0name:
            state0.assertreleasecalled(True)
            state0.assertpostreleasecalled(False)
            state0.assertlockexists(True)

            state1 = teststate(self, d, pidoffset=1)
            lock1 = state1.makelock(parentlock=lock0name)
            state1.assertacquirecalled(True)

            # from within lock1, acquire another lock
            with lock1.inherit() as lock1name:
                # since the file on disk is lock0's this should have the same
                # name
                self.assertEqual(lock0name, lock1name)

                state2 = teststate(self, d, pidoffset=2)
                lock2 = state2.makelock(parentlock=lock1name)
                state2.assertacquirecalled(True)

                lock2.release()
                state2.assertreleasecalled(True)
                state2.assertpostreleasecalled(False)
                state2.assertlockexists(True)

                state1.resetacquirefn()

            state1.assertacquirecalled(True)

            lock1.release()
            state1.assertreleasecalled(True)
            state1.assertpostreleasecalled(False)
            state1.assertlockexists(True)

        lock0.release()

    def testinheritlockfork(self):
        d = tempfile.mkdtemp(dir=encoding.getcwd())
        parentstate = teststate(self, d)
        parentlock = parentstate.makelock()
        parentstate.assertacquirecalled(True)

        # set up lock inheritance
        with parentlock.inherit() as lockname:
            childstate = teststate(self, d, pidoffset=1)
            childlock = childstate.makelock(parentlock=lockname)
            childstate.assertacquirecalled(True)

            # fork the child lock
            forkchildlock = copy.copy(childlock)
            forkchildlock._pidoffset += 1
            forkchildlock.release()
            childstate.assertreleasecalled(False)
            childstate.assertpostreleasecalled(False)
            childstate.assertlockexists(True)

            # release the child lock
            childlock.release()
            childstate.assertreleasecalled(True)
            childstate.assertpostreleasecalled(False)
            childstate.assertlockexists(True)

        parentlock.release()

    def testinheritcheck(self):
        d = tempfile.mkdtemp(dir=encoding.getcwd())
        state = teststate(self, d)
        def check():
            raise error.LockInheritanceContractViolation('check failed')
        lock = state.makelock(inheritchecker=check)
        state.assertacquirecalled(True)

        with self.assertRaises(error.LockInheritanceContractViolation):
            with lock.inherit():
                pass

        lock.release()

    def testfrequentlockunlock(self):
        """This tests whether lock acquisition fails as expected, even if
        (1) lock can't be acquired (makelock fails by EEXIST), and
        (2) locker info can't be read in (readlock fails by ENOENT) while
        retrying 5 times.
        """

        d = tempfile.mkdtemp(dir=encoding.getcwd())
        state = teststate(self, d)

        def emulatefrequentlock(*args):
            raise OSError(errno.EEXIST, "File exists")
        def emulatefrequentunlock(*args):
            raise OSError(errno.ENOENT, "No such file or directory")

        state.vfs.makelock = emulatefrequentlock
        state.vfs.readlock = emulatefrequentunlock

        try:
            state.makelock(timeout=0)
            self.fail("unexpected lock acquisition")
        except error.LockHeld as why:
            self.assertTrue(why.errno == errno.ETIMEDOUT)
            self.assertTrue(why.locker == b"")
            state.assertlockexists(False)

if __name__ == '__main__':
    silenttestrunner.main(__name__)