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bzrlib/tests/test_counted_lock.py
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# Copyright (C) 2007, 2008, 2009 Canonical Ltd
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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"""Tests for bzrlib.counted_lock"""
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from bzrlib.counted_lock import CountedLock
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from bzrlib.errors import (
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    LockError,
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    LockNotHeld,
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    ReadOnlyError,
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    TokenMismatch,
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    )
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from bzrlib.tests import TestCase
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class DummyLock(object):
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    """Lock that just records what's been done to it."""
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    def __init__(self):
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        self._calls = []
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        self._lock_mode = None
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    def is_locked(self):
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        return self._lock_mode is not None
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    def lock_read(self):
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        self._assert_not_locked()
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        self._lock_mode = 'r'
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        self._calls.append('lock_read')
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    def lock_write(self, token=None):
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        if token is not None:
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            if token == 'token':
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                # already held by this caller
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                return 'token'
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            else:
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                raise TokenMismatch()
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        self._assert_not_locked()
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        self._lock_mode = 'w'
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        self._calls.append('lock_write')
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        return 'token'
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    def unlock(self):
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        self._assert_locked()
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        self._lock_mode = None
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        self._calls.append('unlock')
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    def break_lock(self):
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        self._lock_mode = None
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        self._calls.append('break')
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    def _assert_locked(self):
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        if not self._lock_mode:
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            raise LockError("%s is not locked" % (self,))
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    def _assert_not_locked(self):
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        if self._lock_mode:
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            raise LockError("%s is already locked in mode %r" %
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                (self, self._lock_mode))
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    def validate_token(self, token):
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        if token == 'token':
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            # already held by this caller
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            return 'token'
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        elif token is None:
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            return
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        else:
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            raise TokenMismatch(token, 'token')
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83
 
 
84
 
class TestDummyLock(TestCase):
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    def test_lock_initially_not_held(self):
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        l = DummyLock()
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        self.assertFalse(l.is_locked())
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    def test_lock_not_reentrant(self):
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        # can't take the underlying lock twice
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        l = DummyLock()
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        l.lock_read()
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        self.assertRaises(LockError, l.lock_read)
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    def test_detect_underlock(self):
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        l = DummyLock()
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        self.assertRaises(LockError, l.unlock)
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    def test_basic_locking(self):
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        # dummy lock works like a basic non reentrant lock
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        real_lock = DummyLock()
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        self.assertFalse(real_lock.is_locked())
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        # lock read and unlock
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        real_lock.lock_read()
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        self.assertTrue(real_lock.is_locked())
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        real_lock.unlock()
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        self.assertFalse(real_lock.is_locked())
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        # lock write and unlock
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        result = real_lock.lock_write()
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        self.assertEqual('token', result)
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        self.assertTrue(real_lock.is_locked())
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        real_lock.unlock()
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        self.assertFalse(real_lock.is_locked())
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        # check calls
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        self.assertEqual(
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            ['lock_read', 'unlock', 'lock_write', 'unlock'],
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            real_lock._calls)
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    def test_break_lock(self):
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        l = DummyLock()
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        l.lock_write()
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        l.break_lock()
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        self.assertFalse(l.is_locked())
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        self.assertEqual(
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            ['lock_write', 'break'],
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            l._calls)
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class TestCountedLock(TestCase):
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    def test_read_lock(self):
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        # Lock and unlock a counted lock
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        real_lock = DummyLock()
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        l = CountedLock(real_lock)
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        self.assertFalse(l.is_locked())
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        # can lock twice, although this isn't allowed on the underlying lock
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        l.lock_read()
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        l.lock_read()
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        self.assertTrue(l.is_locked())
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        # and release
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        l.unlock()
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        self.assertTrue(l.is_locked())
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        l.unlock()
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        self.assertFalse(l.is_locked())
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        self.assertEquals(
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            ['lock_read', 'unlock'],
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            real_lock._calls)
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    def test_unlock_not_locked(self):
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        real_lock = DummyLock()
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        l = CountedLock(real_lock)
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        self.assertRaises(LockNotHeld, l.unlock)
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    def test_read_lock_while_write_locked(self):
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        real_lock = DummyLock()
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        l = CountedLock(real_lock)
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        l.lock_write()
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        l.lock_read()
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        self.assertEquals('token', l.lock_write())
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        l.unlock()
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        l.unlock()
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        l.unlock()
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        self.assertFalse(l.is_locked())
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        self.assertEquals(
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            ['lock_write', 'unlock'],
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            real_lock._calls)
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    def test_write_lock_while_read_locked(self):
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        real_lock = DummyLock()
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        l = CountedLock(real_lock)
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        l.lock_read()
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        self.assertRaises(ReadOnlyError, l.lock_write)
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        self.assertRaises(ReadOnlyError, l.lock_write)
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        l.unlock()
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        self.assertFalse(l.is_locked())
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        self.assertEquals(
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            ['lock_read', 'unlock'],
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            real_lock._calls)
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    def test_write_lock_reentrant(self):
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        real_lock = DummyLock()
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        l = CountedLock(real_lock)
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        self.assertEqual('token', l.lock_write())
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        self.assertEqual('token', l.lock_write())
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        l.unlock()
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        l.unlock()
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    def test_reenter_with_token(self):
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        real_lock = DummyLock()
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        l1 = CountedLock(real_lock)
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        l2 = CountedLock(real_lock)
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        token = l1.lock_write()
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        self.assertEqual('token', token)
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        # now imagine that we lost that connection, but we still have the
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        # token...
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        del l1
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        # because we can supply the token, we can acquire the lock through
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        # another instance
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        self.assertTrue(real_lock.is_locked())
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        self.assertFalse(l2.is_locked())
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        self.assertEqual(token, l2.lock_write(token=token))
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        self.assertTrue(l2.is_locked())
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        self.assertTrue(real_lock.is_locked())
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        l2.unlock()
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        self.assertFalse(l2.is_locked())
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        self.assertFalse(real_lock.is_locked())
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209
 
    def test_break_lock(self):
210
 
        real_lock = DummyLock()
211
 
        l = CountedLock(real_lock)
212
 
        l.lock_write()
213
 
        l.lock_write()
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        self.assertTrue(real_lock.is_locked())
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        l.break_lock()
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        self.assertFalse(l.is_locked())
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        self.assertFalse(real_lock.is_locked())
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    # TODO: test get_physical_lock_status