def test_missing_lockdir_info(self):
"""We can cope with absent info files."""
t = self.get_transport()
t.mkdir('test_lock')
t.mkdir('test_lock/held')
lf = LockDir(t, 'test_lock')
# In this case we expect the 'not held' result from peek, because peek
# cannot be expected to notice that there is a 'held' directory with no
# 'info' file.
self.assertEqual(None, lf.peek())
# And lock/unlock may work or give LockContention (but not any other
# error).
try:
lf.attempt_lock()
except LockContention:
# LockContention is ok, and expected on Windows
pass
else:
# no error is ok, and expected on POSIX (because POSIX allows
# os.rename over an empty directory).
lf.unlock()
# Currently raises TokenMismatch, but LockCorrupt would be reasonable
# too.
self.assertRaises(
(errors.TokenMismatch, errors.LockCorrupt),
lf.validate_token, 'fake token')
def test_30_lock_wait_fail(self):
"""Wait on a lock, then fail
We ask to wait up to 400ms; this should fail within at most one
second. (Longer times are more realistic but we don't want the test
suite to take too long, and this should do for now.)
"""
t = self.get_transport()
lf1 = LockDir(t, 'test_lock')
lf1.create()
lf2 = LockDir(t, 'test_lock')
self.setup_log_reporter(lf2)
lf1.attempt_lock()
try:
before = time.time()
self.assertRaises(LockContention, lf2.wait_lock,
timeout=0.4, poll=0.1)
after = time.time()
# it should only take about 0.4 seconds, but we allow more time in
# case the machine is heavily loaded
self.assertTrue(after - before <= 8.0,
"took %f seconds to detect lock contention" % (after - before))
finally:
lf1.unlock()
self.assertEqual(1, len(self._logged_reports))
self.assertContainsRe(self._logged_reports[0][0],
r'Unable to obtain lock .* held by jrandom@example\.com on .*'
r' \(process #\d+\), acquired .* ago\.\n'
r'Will continue to try until \d{2}:\d{2}:\d{2}, unless '
r'you press Ctrl-C.\n'
r'See "bzr help break-lock" for more.')
def test_40_confirm_easy(self):
"""Confirm a lock that's already held"""
t = self.get_transport()
lf1 = LockDir(t, 'test_lock')
lf1.create()
lf1.attempt_lock()
lf1.confirm()
def test_40_confirm_easy(self):
"""Confirm a lock that's already held"""
t = self.get_transport()
lf1 = LockDir(t, 'test_lock')
lf1.create()
lf1.attempt_lock()
lf1.confirm()
def test_30_lock_wait_fail(self):
"""Wait on a lock, then fail
We ask to wait up to 400ms; this should fail within at most one
second. (Longer times are more realistic but we don't want the test
suite to take too long, and this should do for now.)
"""
t = self.get_transport()
lf1 = LockDir(t, 'test_lock')
lf1.create()
lf2 = LockDir(t, 'test_lock')
self.setup_log_reporter(lf2)
lf1.attempt_lock()
try:
before = time.time()
self.assertRaises(LockContention, lf2.wait_lock,
timeout=0.4, poll=0.1)
after = time.time()
# it should only take about 0.4 seconds, but we allow more time in
# case the machine is heavily loaded
self.assertTrue(after - before <= 8.0,
"took %f seconds to detect lock contention" % (after - before))
finally:
lf1.unlock()
self.assertEqual(1, len(self._logged_reports))
self.assertContainsRe(self._logged_reports[0][0],
r'Unable to obtain lock .* held by jrandom@example\.com on .*'
r' \(process #\d+\), acquired .* ago\.\n'
r'Will continue to try until \d{2}:\d{2}:\d{2}, unless '
r'you press Ctrl-C.\n'
r'See "bzr help break-lock" for more.')
def test_missing_lockdir_info(self):
"""We can cope with absent info files."""
t = self.get_transport()
t.mkdir('test_lock')
t.mkdir('test_lock/held')
lf = LockDir(t, 'test_lock')
# In this case we expect the 'not held' result from peek, because peek
# cannot be expected to notice that there is a 'held' directory with no
# 'info' file.
self.assertEqual(None, lf.peek())
# And lock/unlock may work or give LockContention (but not any other
# error).
try:
lf.attempt_lock()
except LockContention:
# LockContention is ok, and expected on Windows
pass
else:
# no error is ok, and expected on POSIX (because POSIX allows
# os.rename over an empty directory).
lf.unlock()
# Currently raises TokenMismatch, but LockCorrupt would be reasonable
# too.
self.assertRaises(
(errors.TokenMismatch, errors.LockCorrupt),
lf.validate_token, 'fake token')
def test_42_confirm_broken_manually(self):
"""Confirm a lock broken by hand"""
t = self.get_transport()
lf1 = LockDir(t, 'test_lock')
lf1.create()
lf1.attempt_lock()
t.move('test_lock', 'lock_gone_now')
self.assertRaises(LockBroken, lf1.confirm)
def test_42_confirm_broken_manually(self):
"""Confirm a lock broken by hand"""
t = self.get_transport()
lf1 = LockDir(t, 'test_lock')
lf1.create()
lf1.attempt_lock()
t.move('test_lock', 'lock_gone_now')
self.assertRaises(LockBroken, lf1.confirm)
def test_21_peek_readonly(self):
"""Peek over a readonly transport"""
t = self.get_transport()
lf1 = LockDir(t, 'test_lock')
lf1.create()
lf2 = LockDir(self.get_readonly_transport(), 'test_lock')
self.assertEqual(lf2.peek(), None)
lf1.attempt_lock()
info2 = lf2.peek()
self.assertTrue(info2)
self.assertEqual(info2['nonce'], lf1.nonce)
def test_21_peek_readonly(self):
"""Peek over a readonly transport"""
t = self.get_transport()
lf1 = LockDir(t, 'test_lock')
lf1.create()
lf2 = LockDir(self.get_readonly_transport(), 'test_lock')
self.assertEqual(lf2.peek(), None)
lf1.attempt_lock()
info2 = lf2.peek()
self.assertTrue(info2)
self.assertEqual(info2['nonce'], lf1.nonce)
def test_10_lock_uncontested(self):
"""Acquire and release a lock"""
t = self.get_transport()
lf = LockDir(t, 'test_lock')
lf.create()
lf.attempt_lock()
try:
self.assertTrue(lf.is_held)
finally:
lf.unlock()
self.assertFalse(lf.is_held)
def test_10_lock_uncontested(self):
"""Acquire and release a lock"""
t = self.get_transport()
lf = LockDir(t, 'test_lock')
lf.create()
lf.attempt_lock()
try:
self.assertTrue(lf.is_held)
finally:
lf.unlock()
self.assertFalse(lf.is_held)
def test_32_lock_wait_succeed(self):
"""Succeed when trying to acquire a lock that gets released
One thread holds on a lock and then releases it; another
tries to lock it.
"""
# This test sometimes fails like this:
# Traceback (most recent call last):
# File "/home/pqm/bzr-pqm-workdir/home/+trunk/bzrlib/tests/
# test_lockdir.py", line 247, in test_32_lock_wait_succeed
# self.assertEqual(1, len(self._logged_reports))
# AssertionError: not equal:
# a = 1
# b = 0
raise tests.TestSkipped("Test fails intermittently")
t = self.get_transport()
lf1 = LockDir(t, 'test_lock')
lf1.create()
lf1.attempt_lock()
def wait_and_unlock():
time.sleep(0.1)
lf1.unlock()
unlocker = Thread(target=wait_and_unlock)
unlocker.start()
try:
lf2 = LockDir(t, 'test_lock')
self.setup_log_reporter(lf2)
before = time.time()
# wait and then lock
lf2.wait_lock(timeout=0.4, poll=0.1)
after = time.time()
self.assertTrue(after - before <= 1.0)
finally:
unlocker.join()
# There should be only 1 report, even though it should have to
# wait for a while
lock_base = lf2.transport.abspath(lf2.path)
self.assertEqual(1, len(self._logged_reports))
self.assertEqual(
'%s %s\n'
'%s\n%s\n'
'Will continue to try until %s\n', self._logged_reports[0][0])
args = self._logged_reports[0][1]
self.assertEqual('Unable to obtain', args[0])
self.assertEqual('lock %s' % (lock_base, ), args[1])
self.assertStartsWith(args[2], 'held by ')
self.assertStartsWith(args[3], 'locked ')
self.assertEndsWith(args[3], ' ago')
self.assertContainsRe(args[4], r'\d\d:\d\d:\d\d')
def test_32_lock_wait_succeed(self):
"""Succeed when trying to acquire a lock that gets released
One thread holds on a lock and then releases it; another
tries to lock it.
"""
# This test sometimes fails like this:
# Traceback (most recent call last):
# File "/home/pqm/bzr-pqm-workdir/home/+trunk/bzrlib/tests/
# test_lockdir.py", line 247, in test_32_lock_wait_succeed
# self.assertEqual(1, len(self._logged_reports))
# AssertionError: not equal:
# a = 1
# b = 0
raise tests.TestSkipped("Test fails intermittently")
t = self.get_transport()
lf1 = LockDir(t, 'test_lock')
lf1.create()
lf1.attempt_lock()
def wait_and_unlock():
time.sleep(0.1)
lf1.unlock()
unlocker = Thread(target=wait_and_unlock)
unlocker.start()
try:
lf2 = LockDir(t, 'test_lock')
self.setup_log_reporter(lf2)
before = time.time()
# wait and then lock
lf2.wait_lock(timeout=0.4, poll=0.1)
after = time.time()
self.assertTrue(after - before <= 1.0)
finally:
unlocker.join()
# There should be only 1 report, even though it should have to
# wait for a while
lock_base = lf2.transport.abspath(lf2.path)
self.assertEqual(1, len(self._logged_reports))
self.assertEqual('%s %s\n'
'%s\n%s\n'
'Will continue to try until %s\n',
self._logged_reports[0][0])
args = self._logged_reports[0][1]
self.assertEqual('Unable to obtain', args[0])
self.assertEqual('lock %s' % (lock_base,), args[1])
self.assertStartsWith(args[2], 'held by ')
self.assertStartsWith(args[3], 'locked ')
self.assertEndsWith(args[3], ' ago')
self.assertContainsRe(args[4], r'\d\d:\d\d:\d\d')
def test_lock_with_buggy_rename(self):
# test that lock acquisition handles servers which pretend they
# renamed correctly but that actually fail
t = transport.get_transport('brokenrename+' + self.get_url())
ld1 = LockDir(t, 'test_lock')
ld1.create()
ld1.attempt_lock()
ld2 = LockDir(t, 'test_lock')
# we should fail to lock
e = self.assertRaises(errors.LockContention, ld2.attempt_lock)
# now the original caller should succeed in unlocking
ld1.unlock()
# and there should be nothing left over
self.assertEquals([], t.list_dir('test_lock'))
def test_lock_with_buggy_rename(self):
# test that lock acquisition handles servers which pretend they
# renamed correctly but that actually fail
t = transport.get_transport('brokenrename+' + self.get_url())
ld1 = LockDir(t, 'test_lock')
ld1.create()
ld1.attempt_lock()
ld2 = LockDir(t, 'test_lock')
# we should fail to lock
e = self.assertRaises(errors.LockContention, ld2.attempt_lock)
# now the original caller should succeed in unlocking
ld1.unlock()
# and there should be nothing left over
self.assertEquals([], t.list_dir('test_lock'))
def test_20_lock_contested(self):
"""Contention to get a lock"""
t = self.get_transport()
lf1 = LockDir(t, 'test_lock')
lf1.create()
lf1.attempt_lock()
lf2 = LockDir(t, 'test_lock')
try:
# locking is between LockDir instances; aliases within
# a single process are not detected
lf2.attempt_lock()
self.fail('Failed to detect lock collision')
except LockContention, e:
self.assertEqual(e.lock, lf2)
self.assertContainsRe(str(e), r'^Could not acquire.*test_lock.*$')
def test_44_break_already_released(self):
"""Lock break races with regular release"""
t = self.get_transport()
lf1 = LockDir(t, 'test_lock')
lf1.create()
lf1.attempt_lock()
# someone else sees it's still locked
lf2 = LockDir(t, 'test_lock')
holder_info = lf2.peek()
# in the interim the lock is released
lf1.unlock()
# break should succeed
lf2.force_break(holder_info)
# now we should be able to take it
lf2.attempt_lock()
lf2.confirm()
def test_20_lock_peek(self):
"""Peek at the state of a lock"""
t = self.get_transport()
lf1 = LockDir(t, 'test_lock')
lf1.create()
lf1.attempt_lock()
# lock is held, should get some info on it
info1 = lf1.peek()
self.assertEqual(set(info1.keys()),
set(['user', 'nonce', 'hostname', 'pid', 'start_time']))
# should get the same info if we look at it through a different
# instance
info2 = LockDir(t, 'test_lock').peek()
self.assertEqual(info1, info2)
# locks which are never used should be not-held
self.assertEqual(LockDir(t, 'other_lock').peek(), None)
def test_45_break_mismatch(self):
"""Lock break races with someone else acquiring it"""
t = self.get_transport()
lf1 = LockDir(t, 'test_lock')
lf1.create()
lf1.attempt_lock()
# someone else sees it's still locked
lf2 = LockDir(t, 'test_lock')
holder_info = lf2.peek()
# in the interim the lock is released
lf1.unlock()
lf3 = LockDir(t, 'test_lock')
lf3.attempt_lock()
# break should now *fail*
self.assertRaises(LockBreakMismatch, lf2.force_break, holder_info)
lf3.unlock()
def test_43_break(self):
"""Break a lock whose caller has forgotten it"""
t = self.get_transport()
lf1 = LockDir(t, 'test_lock')
lf1.create()
lf1.attempt_lock()
# we incorrectly discard the lock object without unlocking it
del lf1
# someone else sees it's still locked
lf2 = LockDir(t, 'test_lock')
holder_info = lf2.peek()
self.assertTrue(holder_info)
lf2.force_break(holder_info)
# now we should be able to take it
lf2.attempt_lock()
lf2.confirm()
def test_43_break(self):
"""Break a lock whose caller has forgotten it"""
t = self.get_transport()
lf1 = LockDir(t, 'test_lock')
lf1.create()
lf1.attempt_lock()
# we incorrectly discard the lock object without unlocking it
del lf1
# someone else sees it's still locked
lf2 = LockDir(t, 'test_lock')
holder_info = lf2.peek()
self.assertTrue(holder_info)
lf2.force_break(holder_info)
# now we should be able to take it
lf2.attempt_lock()
lf2.confirm()
def test_44_break_already_released(self):
"""Lock break races with regular release"""
t = self.get_transport()
lf1 = LockDir(t, 'test_lock')
lf1.create()
lf1.attempt_lock()
# someone else sees it's still locked
lf2 = LockDir(t, 'test_lock')
holder_info = lf2.peek()
# in the interim the lock is released
lf1.unlock()
# break should succeed
lf2.force_break(holder_info)
# now we should be able to take it
lf2.attempt_lock()
lf2.confirm()
def test_20_lock_contested(self):
"""Contention to get a lock"""
t = self.get_transport()
lf1 = LockDir(t, 'test_lock')
lf1.create()
lf1.attempt_lock()
lf2 = LockDir(t, 'test_lock')
try:
# locking is between LockDir instances; aliases within
# a single process are not detected
lf2.attempt_lock()
self.fail('Failed to detect lock collision')
except LockContention, e:
self.assertEqual(e.lock, lf2)
self.assertContainsRe(str(e),
r'^Could not acquire.*test_lock.*$')
def test_20_lock_peek(self):
"""Peek at the state of a lock"""
t = self.get_transport()
lf1 = LockDir(t, 'test_lock')
lf1.create()
lf1.attempt_lock()
self.addCleanup(lf1.unlock)
# lock is held, should get some info on it
info1 = lf1.peek()
self.assertEqual(set(info1.info_dict.keys()),
set(['user', 'nonce', 'hostname', 'pid', 'start_time']))
# should get the same info if we look at it through a different
# instance
info2 = LockDir(t, 'test_lock').peek()
self.assertEqual(info1, info2)
# locks which are never used should be not-held
self.assertEqual(LockDir(t, 'other_lock').peek(), None)
def test_45_break_mismatch(self):
"""Lock break races with someone else acquiring it"""
t = self.get_transport()
lf1 = LockDir(t, 'test_lock')
lf1.create()
lf1.attempt_lock()
# someone else sees it's still locked
lf2 = LockDir(t, 'test_lock')
holder_info = lf2.peek()
# in the interim the lock is released
lf1.unlock()
lf3 = LockDir(t, 'test_lock')
lf3.attempt_lock()
# break should now *fail*
self.assertRaises(LockBreakMismatch, lf2.force_break,
holder_info)
lf3.unlock()
def test_30_lock_wait_fail(self):
"""Wait on a lock, then fail
We ask to wait up to 400ms; this should fail within at most one
second. (Longer times are more realistic but we don't want the test
suite to take too long, and this should do for now.)
"""
t = self.get_transport()
lf1 = LockDir(t, 'test_lock')
lf1.create()
lf2 = LockDir(t, 'test_lock')
self.setup_log_reporter(lf2)
lf1.attempt_lock()
try:
before = time.time()
self.assertRaises(LockContention,
lf2.wait_lock,
timeout=0.4,
poll=0.1)
after = time.time()
# it should only take about 0.4 seconds, but we allow more time in
# case the machine is heavily loaded
self.assertTrue(
after - before <= 8.0,
"took %f seconds to detect lock contention" % (after - before))
finally:
lf1.unlock()
lock_base = lf2.transport.abspath(lf2.path)
self.assertEqual(1, len(self._logged_reports))
lock_url = lf2.transport.abspath(lf2.path)
self.assertEqual(
'%s %s\n'
'%s\n%s\n'
'Will continue to try until %s, unless '
'you press Ctrl-C\n'
'If you\'re sure that it\'s not being '
'modified, use bzr break-lock %s', self._logged_reports[0][0])
args = self._logged_reports[0][1]
self.assertEqual('Unable to obtain', args[0])
self.assertEqual('lock %s' % (lock_base, ), args[1])
self.assertStartsWith(args[2], 'held by ')
self.assertStartsWith(args[3], 'locked ')
self.assertEndsWith(args[3], ' ago')
self.assertContainsRe(args[4], r'\d\d:\d\d:\d\d')
def test_34_lock_write_waits(self):
"""LockDir.lock_write() will wait for the lock."""
# the test suite sets the default to 0 to make deadlocks fail fast.
# change it for this test, as we want to try a manual deadlock.
raise tests.TestSkipped('Timing-sensitive test')
bzrlib.lockdir._DEFAULT_TIMEOUT_SECONDS = 300
t = self.get_transport()
lf1 = LockDir(t, 'test_lock')
lf1.create()
lf1.attempt_lock()
def wait_and_unlock():
time.sleep(0.1)
lf1.unlock()
unlocker = Thread(target=wait_and_unlock)
unlocker.start()
try:
lf2 = LockDir(t, 'test_lock')
self.setup_log_reporter(lf2)
before = time.time()
# wait and then lock
lf2.lock_write()
after = time.time()
finally:
unlocker.join()
# There should be only 1 report, even though it should have to
# wait for a while
lock_base = lf2.transport.abspath(lf2.path)
self.assertEqual(1, len(self._logged_reports))
self.assertEqual(
'%s %s\n'
'%s\n%s\n'
'Will continue to try until %s\n', self._logged_reports[0][0])
args = self._logged_reports[0][1]
self.assertEqual('Unable to obtain', args[0])
self.assertEqual('lock %s' % (lock_base, ), args[1])
self.assertStartsWith(args[2], 'held by ')
self.assertStartsWith(args[3], 'locked ')
self.assertEndsWith(args[3], ' ago')
self.assertContainsRe(args[4], r'\d\d:\d\d:\d\d')
def test_30_lock_wait_fail(self):
"""Wait on a lock, then fail
We ask to wait up to 400ms; this should fail within at most one
second. (Longer times are more realistic but we don't want the test
suite to take too long, and this should do for now.)
"""
t = self.get_transport()
lf1 = LockDir(t, 'test_lock')
lf1.create()
lf2 = LockDir(t, 'test_lock')
self.setup_log_reporter(lf2)
lf1.attempt_lock()
try:
before = time.time()
self.assertRaises(LockContention, lf2.wait_lock,
timeout=0.4, poll=0.1)
after = time.time()
# it should only take about 0.4 seconds, but we allow more time in
# case the machine is heavily loaded
self.assertTrue(after - before <= 8.0,
"took %f seconds to detect lock contention" % (after - before))
finally:
lf1.unlock()
lock_base = lf2.transport.abspath(lf2.path)
self.assertEqual(1, len(self._logged_reports))
lock_url = lf2.transport.abspath(lf2.path)
self.assertEqual('%s %s\n'
'%s\n%s\n'
'Will continue to try until %s, unless '
'you press Ctrl-C\n'
'If you\'re sure that it\'s not being '
'modified, use bzr break-lock %s',
self._logged_reports[0][0])
args = self._logged_reports[0][1]
self.assertEqual('Unable to obtain', args[0])
self.assertEqual('lock %s' % (lock_base,), args[1])
self.assertStartsWith(args[2], 'held by ')
self.assertStartsWith(args[3], 'locked ')
self.assertEndsWith(args[3], ' ago')
self.assertContainsRe(args[4], r'\d\d:\d\d:\d\d')
def test_34_lock_write_waits(self):
"""LockDir.lock_write() will wait for the lock."""
# the test suite sets the default to 0 to make deadlocks fail fast.
# change it for this test, as we want to try a manual deadlock.
raise tests.TestSkipped('Timing-sensitive test')
bzrlib.lockdir._DEFAULT_TIMEOUT_SECONDS = 300
t = self.get_transport()
lf1 = LockDir(t, 'test_lock')
lf1.create()
lf1.attempt_lock()
def wait_and_unlock():
time.sleep(0.1)
lf1.unlock()
unlocker = Thread(target=wait_and_unlock)
unlocker.start()
try:
lf2 = LockDir(t, 'test_lock')
self.setup_log_reporter(lf2)
before = time.time()
# wait and then lock
lf2.lock_write()
after = time.time()
finally:
unlocker.join()
# There should be only 1 report, even though it should have to
# wait for a while
lock_base = lf2.transport.abspath(lf2.path)
self.assertEqual(1, len(self._logged_reports))
self.assertEqual('%s %s\n'
'%s\n%s\n'
'Will continue to try until %s\n',
self._logged_reports[0][0])
args = self._logged_reports[0][1]
self.assertEqual('Unable to obtain', args[0])
self.assertEqual('lock %s' % (lock_base,), args[1])
self.assertStartsWith(args[2], 'held by ')
self.assertStartsWith(args[3], 'locked ')
self.assertEndsWith(args[3], ' ago')
self.assertContainsRe(args[4], r'\d\d:\d\d:\d\d')
def test_auto_break_stale_lock_configured_off(self):
"""Automatic breaking can be turned off"""
l1 = LockDir(self.get_transport(), 'a',
extra_holder_info={'pid': '12312313'})
token_1 = l1.attempt_lock()
self.addCleanup(l1.unlock)
l2 = LockDir(self.get_transport(), 'a')
# This fails now, because dead lock breaking is off by default.
self.assertRaises(LockContention,
l2.attempt_lock)
# and it's in fact not broken
l1.confirm()
def test_auto_break_stale_lock_configured_off(self):
"""Automatic breaking can be turned off"""
l1 = LockDir(self.get_transport(), 'a',
extra_holder_info={'pid': '12312313'})
token_1 = l1.attempt_lock()
self.addCleanup(l1.unlock)
l2 = LockDir(self.get_transport(), 'a')
# This fails now, because dead lock breaking is off by default.
self.assertRaises(LockContention,
l2.attempt_lock)
# and it's in fact not broken
l1.confirm()
def test_auto_break_stale_lock(self):
"""Locks safely known to be stale are just cleaned up.
This generates a warning but no other user interaction.
"""
self.overrideAttr(lockdir, 'get_host_name',
lambda: 'aproperhostname')
# This is off by default at present; see the discussion in the bug.
# If you change the default, don't forget to update the docs.
config.GlobalStack().set('locks.steal_dead', True)
# Create a lock pretending to come from a different nonexistent
# process on the same machine.
l1 = LockDir(self.get_transport(), 'a',
extra_holder_info={'pid': '12312313'})
token_1 = l1.attempt_lock()
l2 = LockDir(self.get_transport(), 'a')
token_2 = l2.attempt_lock()
# l1 will notice its lock was stolen.
self.assertRaises(errors.LockBroken,
l1.unlock)
l2.unlock()
def test_auto_break_stale_lock(self):
"""Locks safely known to be stale are just cleaned up.
This generates a warning but no other user interaction.
"""
self.overrideAttr(lockdir, 'get_host_name',
lambda: 'aproperhostname')
# This is off by default at present; see the discussion in the bug.
# If you change the default, don't forget to update the docs.
config.GlobalConfig().set_user_option('locks.steal_dead', True)
# Create a lock pretending to come from a different nonexistent
# process on the same machine.
l1 = LockDir(self.get_transport(), 'a',
extra_holder_info={'pid': '12312313'})
token_1 = l1.attempt_lock()
l2 = LockDir(self.get_transport(), 'a')
token_2 = l2.attempt_lock()
# l1 will notice its lock was stolen.
self.assertRaises(errors.LockBroken,
l1.unlock)
l2.unlock()
