view tests/test-atomictempfile.py @ 42943:5fadf6103790

remotefilelog: replace repack lock to solve race condition

2c74337e6483 reduced the probability of race-conditions when starting
background repack and prefetch and we saw the difference in our CI instance
with all failures disappearing except one where one call to waitonrepack seems
to returns too early.

I'm not sure what exactly goes wrong but I realized that while the prefetch
operation uses a standard Mercurial lock, the repack operation is using a
custom lock based on `fcntl.flock` on available platforms. As `extutil.flock`
fallback on traditional Mercurial locks on other platforms and the tests are
stable on my laptop, our CI environment and GCC112, I'm sending this patch to
standardize the behavior across environments.

Differential Revision: https://phab.mercurial-scm.org/D6844

from __future__ import absolute_import

import glob
import os
import shutil
import stat
import tempfile
import unittest

from mercurial import (
    pycompat,
    util,
)
atomictempfile = util.atomictempfile

if pycompat.ispy3:
    xrange = range

class testatomictempfile(unittest.TestCase):
    def setUp(self):
        self._testdir = tempfile.mkdtemp(b'atomictempfiletest')
        self._filename = os.path.join(self._testdir, b'testfilename')

    def tearDown(self):
        shutil.rmtree(self._testdir, True)

    def testsimple(self):
        file = atomictempfile(self._filename)
        self.assertFalse(os.path.isfile(self._filename))
        tempfilename = file._tempname
        self.assertTrue(tempfilename in glob.glob(
            os.path.join(self._testdir, b'.testfilename-*')))

        file.write(b'argh\n')
        file.close()

        self.assertTrue(os.path.isfile(self._filename))
        self.assertTrue(tempfilename not in glob.glob(
            os.path.join(self._testdir, b'.testfilename-*')))

    # discard() removes the temp file without making the write permanent
    def testdiscard(self):
        file = atomictempfile(self._filename)
        (dir, basename) = os.path.split(file._tempname)

        file.write(b'yo\n')
        file.discard()

        self.assertFalse(os.path.isfile(self._filename))
        self.assertTrue(basename not in os.listdir(b'.'))

    # if a programmer screws up and passes bad args to atomictempfile, they
    # get a plain ordinary TypeError, not infinite recursion
    def testoops(self):
        with self.assertRaises(TypeError):
            atomictempfile()

    # checkambig=True avoids ambiguity of timestamp
    def testcheckambig(self):
        def atomicwrite(checkambig):
            f = atomictempfile(self._filename, checkambig=checkambig)
            f.write(b'FOO')
            f.close()

        # try some times, because reproduction of ambiguity depends on
        # "filesystem time"
        for i in xrange(5):
            atomicwrite(False)
            oldstat = os.stat(self._filename)
            if oldstat[stat.ST_CTIME] != oldstat[stat.ST_MTIME]:
                # subsequent changing never causes ambiguity
                continue

            repetition = 3

            # repeat atomic write with checkambig=True, to examine
            # whether st_mtime is advanced multiple times as expected
            for j in xrange(repetition):
                atomicwrite(True)
            newstat = os.stat(self._filename)
            if oldstat[stat.ST_CTIME] != newstat[stat.ST_CTIME]:
                # timestamp ambiguity was naturally avoided while repetition
                continue

            # st_mtime should be advanced "repetition" times, because
            # all atomicwrite() occurred at same time (in sec)
            oldtime = (oldstat[stat.ST_MTIME] + repetition) & 0x7fffffff
            self.assertTrue(newstat[stat.ST_MTIME] == oldtime)
            # no more examination is needed, if assumption above is true
            break
        else:
            # This platform seems too slow to examine anti-ambiguity
            # of file timestamp (or test happened to be executed at
            # bad timing). Exit silently in this case, because running
            # on other faster platforms can detect problems
            pass

    def testread(self):
        with open(self._filename, 'wb') as f:
            f.write(b'foobar\n')
        file = atomictempfile(self._filename, mode=b'rb')
        self.assertTrue(file.read(), b'foobar\n')
        file.discard()

    def testcontextmanagersuccess(self):
        """When the context closes, the file is closed"""
        with atomictempfile(b'foo') as f:
            self.assertFalse(os.path.isfile(b'foo'))
            f.write(b'argh\n')
        self.assertTrue(os.path.isfile(b'foo'))

    def testcontextmanagerfailure(self):
        """On exception, the file is discarded"""
        try:
            with atomictempfile(b'foo') as f:
                self.assertFalse(os.path.isfile(b'foo'))
                f.write(b'argh\n')
                raise ValueError
        except ValueError:
            pass
        self.assertFalse(os.path.isfile(b'foo'))

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