# Copyright (c) 2005 Divmod, Inc.
# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.

"""
Tests for L{twisted.python.lockfile}.
"""

import os, errno

from twisted.trial import unittest
from twisted.python import lockfile
from twisted.python.runtime import platform

skipKill = None
if platform.isWindows():
try:
from win32api import OpenProcess
import pywintypes
except ImportError:
skipKill = ("On windows, lockfile.kill is not implemented in the "
"absence of win32api and/or pywintypes.")

class UtilTests(unittest.TestCase):
"""
Tests for the helper functions used to implement L{FilesystemLock}.
"""
def test_symlinkEEXIST(self):
"""
L{lockfile.symlink} raises L{OSError} with C{errno} set to L{EEXIST}
when an attempt is made to create a symlink which already exists.
"""
name = self.mktemp()
lockfile.symlink('foo', name)
exc = self.assertRaises(OSError, lockfile.symlink, 'foo', name)
self.assertEqual(exc.errno, errno.EEXIST)


def test_symlinkEIOWindows(self):
"""
L{lockfile.symlink} raises L{OSError} with C{errno} set to L{EIO} when
the underlying L{rename} call fails with L{EIO}.

Renaming a file on Windows may fail if the target of the rename is in
the process of being deleted (directory deletion appears not to be
atomic).
"""
name = self.mktemp()
def fakeRename(src, dst):
raise IOError(errno.EIO, None)
self.patch(lockfile, 'rename', fakeRename)
exc = self.assertRaises(IOError, lockfile.symlink, name, "foo")
self.assertEqual(exc.errno, errno.EIO)
if not platform.isWindows():
test_symlinkEIOWindows.skip = (
"special rename EIO handling only necessary and correct on "
"Windows.")


def test_readlinkENOENT(self):
"""
L{lockfile.readlink} raises L{OSError} with C{errno} set to L{ENOENT}
when an attempt is made to read a symlink which does not exist.
"""
name = self.mktemp()
exc = self.assertRaises(OSError, lockfile.readlink, name)
self.assertEqual(exc.errno, errno.ENOENT)


def test_readlinkEACCESWindows(self):
"""
L{lockfile.readlink} raises L{OSError} with C{errno} set to L{EACCES}
on Windows when the underlying file open attempt fails with C{EACCES}.

Opening a file on Windows may fail if the path is inside a directory
which is in the process of being deleted (directory deletion appears
not to be atomic).
"""
name = self.mktemp()
def fakeOpen(path, mode):
raise IOError(errno.EACCES, None)
self.patch(lockfile, '_open', fakeOpen)
exc = self.assertRaises(IOError, lockfile.readlink, name)
self.assertEqual(exc.errno, errno.EACCES)
if not platform.isWindows():
test_readlinkEACCESWindows.skip = (
"special readlink EACCES handling only necessary and correct on "
"Windows.")


def test_kill(self):
"""
L{lockfile.kill} returns without error if passed the PID of a
process which exists and signal C{0}.
"""
lockfile.kill(os.getpid(), 0)
test_kill.skip = skipKill


def test_killESRCH(self):
"""
L{lockfile.kill} raises L{OSError} with errno of L{ESRCH} if
passed a PID which does not correspond to any process.
"""
# Hopefully there is no process with PID 2 ** 31 - 1
exc = self.assertRaises(OSError, lockfile.kill, 2 ** 31 - 1, 0)
self.assertEqual(exc.errno, errno.ESRCH)
test_killESRCH.skip = skipKill


def test_noKillCall(self):
"""
Verify that when L{lockfile.kill} does end up as None (e.g. on Windows
without pywin32), it doesn't end up being called and raising a
L{TypeError}.
"""
self.patch(lockfile, "kill", None)
fl = lockfile.FilesystemLock(self.mktemp())
fl.lock()
self.assertFalse(fl.lock())



class LockingTestCase(unittest.TestCase):
def _symlinkErrorTest(self, errno):
def fakeSymlink(source, dest):
raise OSError(errno, None)
self.patch(lockfile, 'symlink', fakeSymlink)

lockf = self.mktemp()
lock = lockfile.FilesystemLock(lockf)
exc = self.assertRaises(OSError, lock.lock)
self.assertEqual(exc.errno, errno)


def test_symlinkError(self):
"""
An exception raised by C{symlink} other than C{EEXIST} is passed up to
the caller of L{FilesystemLock.lock}.
"""
self._symlinkErrorTest(errno.ENOSYS)


def test_symlinkErrorPOSIX(self):
"""
An L{OSError} raised by C{symlink} on a POSIX platform with an errno of
C{EACCES} or C{EIO} is passed to the caller of L{FilesystemLock.lock}.

On POSIX, unlike on Windows, these are unexpected errors which cannot
be handled by L{FilesystemLock}.
"""
self._symlinkErrorTest(errno.EACCES)
self._symlinkErrorTest(errno.EIO)
if platform.isWindows():
test_symlinkErrorPOSIX.skip = (
"POSIX-specific error propagation not expected on Windows.")


def test_cleanlyAcquire(self):
"""
If the lock has never been held, it can be acquired and the C{clean}
and C{locked} attributes are set to C{True}.
"""
lockf = self.mktemp()
lock = lockfile.FilesystemLock(lockf)
self.assertTrue(lock.lock())
self.assertTrue(lock.clean)
self.assertTrue(lock.locked)


def test_cleanlyRelease(self):
"""
If a lock is released cleanly, it can be re-acquired and the C{clean}
and C{locked} attributes are set to C{True}.
"""
lockf = self.mktemp()
lock = lockfile.FilesystemLock(lockf)
self.assertTrue(lock.lock())
lock.unlock()
self.assertFalse(lock.locked)

lock = lockfile.FilesystemLock(lockf)
self.assertTrue(lock.lock())
self.assertTrue(lock.clean)
self.assertTrue(lock.locked)


def test_cannotLockLocked(self):
"""
If a lock is currently locked, it cannot be locked again.
"""
lockf = self.mktemp()
firstLock = lockfile.FilesystemLock(lockf)
self.assertTrue(firstLock.lock())

secondLock = lockfile.FilesystemLock(lockf)
self.assertFalse(secondLock.lock())
self.assertFalse(secondLock.locked)


def test_uncleanlyAcquire(self):
"""
If a lock was held by a process which no longer exists, it can be
acquired, the C{clean} attribute is set to C{False}, and the
C{locked} attribute is set to C{True}.
"""
owner = 12345

def fakeKill(pid, signal):
if signal != 0:
raise OSError(errno.EPERM, None)
if pid == owner:
raise OSError(errno.ESRCH, None)

lockf = self.mktemp()
self.patch(lockfile, 'kill', fakeKill)
lockfile.symlink(str(owner), lockf)

lock = lockfile.FilesystemLock(lockf)
self.assertTrue(lock.lock())
self.assertFalse(lock.clean)
self.assertTrue(lock.locked)

self.assertEqual(lockfile.readlink(lockf), str(os.getpid()))


def test_lockReleasedBeforeCheck(self):
"""
If the lock is initially held but then released before it can be
examined to determine if the process which held it still exists, it is
acquired and the C{clean} and C{locked} attributes are set to C{True}.
"""
def fakeReadlink(name):
# Pretend to be another process releasing the lock.
lockfile.rmlink(lockf)
# Fall back to the real implementation of readlink.
readlinkPatch.restore()
return lockfile.readlink(name)
readlinkPatch = self.patch(lockfile, 'readlink', fakeReadlink)

def fakeKill(pid, signal):
if signal != 0:
raise OSError(errno.EPERM, None)
if pid == 43125:
raise OSError(errno.ESRCH, None)
self.patch(lockfile, 'kill', fakeKill)

lockf = self.mktemp()
lock = lockfile.FilesystemLock(lockf)
lockfile.symlink(str(43125), lockf)
self.assertTrue(lock.lock())
self.assertTrue(lock.clean)
self.assertTrue(lock.locked)


def test_lockReleasedDuringAcquireSymlink(self):
"""
If the lock is released while an attempt is made to acquire
it, the lock attempt fails and C{FilesystemLock.lock} returns
C{False}. This can happen on Windows when L{lockfile.symlink}
fails with L{IOError} of C{EIO} because another process is in
the middle of a call to L{os.rmdir} (implemented in terms of
RemoveDirectory) which is not atomic.
"""
def fakeSymlink(src, dst):
# While another process id doing os.rmdir which the Windows
# implementation of rmlink does, a rename call will fail with EIO.
raise OSError(errno.EIO, None)

self.patch(lockfile, 'symlink', fakeSymlink)

lockf = self.mktemp()
lock = lockfile.FilesystemLock(lockf)
self.assertFalse(lock.lock())
self.assertFalse(lock.locked)
if not platform.isWindows():
test_lockReleasedDuringAcquireSymlink.skip = (
"special rename EIO handling only necessary and correct on "
"Windows.")


def test_lockReleasedDuringAcquireReadlink(self):
"""
If the lock is initially held but is released while an attempt
is made to acquire it, the lock attempt fails and
L{FilesystemLock.lock} returns C{False}.
"""
def fakeReadlink(name):
# While another process is doing os.rmdir which the
# Windows implementation of rmlink does, a readlink call
# will fail with EACCES.
raise IOError(errno.EACCES, None)
readlinkPatch = self.patch(lockfile, 'readlink', fakeReadlink)

lockf = self.mktemp()
lock = lockfile.FilesystemLock(lockf)
lockfile.symlink(str(43125), lockf)
self.assertFalse(lock.lock())
self.assertFalse(lock.locked)
if not platform.isWindows():
test_lockReleasedDuringAcquireReadlink.skip = (
"special readlink EACCES handling only necessary and correct on "
"Windows.")


def _readlinkErrorTest(self, exceptionType, errno):
def fakeReadlink(name):
raise exceptionType(errno, None)
self.patch(lockfile, 'readlink', fakeReadlink)

lockf = self.mktemp()

# Make it appear locked so it has to use readlink
lockfile.symlink(str(43125), lockf)

lock = lockfile.FilesystemLock(lockf)
exc = self.assertRaises(exceptionType, lock.lock)
self.assertEqual(exc.errno, errno)
self.assertFalse(lock.locked)


def test_readlinkError(self):
"""
An exception raised by C{readlink} other than C{ENOENT} is passed up to
the caller of L{FilesystemLock.lock}.
"""
self._readlinkErrorTest(OSError, errno.ENOSYS)
self._readlinkErrorTest(IOError, errno.ENOSYS)


def test_readlinkErrorPOSIX(self):
"""
Any L{IOError} raised by C{readlink} on a POSIX platform passed to the
caller of L{FilesystemLock.lock}.

On POSIX, unlike on Windows, these are unexpected errors which cannot
be handled by L{FilesystemLock}.
"""
self._readlinkErrorTest(IOError, errno.ENOSYS)
self._readlinkErrorTest(IOError, errno.EACCES)
if platform.isWindows():
test_readlinkErrorPOSIX.skip = (
"POSIX-specific error propagation not expected on Windows.")


def test_lockCleanedUpConcurrently(self):
"""
If a second process cleans up the lock after a first one checks the
lock and finds that no process is holding it, the first process does
not fail when it tries to clean up the lock.
"""
def fakeRmlink(name):
rmlinkPatch.restore()
# Pretend to be another process cleaning up the lock.
lockfile.rmlink(lockf)
# Fall back to the real implementation of rmlink.
return lockfile.rmlink(name)
rmlinkPatch = self.patch(lockfile, 'rmlink', fakeRmlink)

def fakeKill(pid, signal):
if signal != 0:
raise OSError(errno.EPERM, None)
if pid == 43125:
raise OSError(errno.ESRCH, None)
self.patch(lockfile, 'kill', fakeKill)

lockf = self.mktemp()
lock = lockfile.FilesystemLock(lockf)
lockfile.symlink(str(43125), lockf)
self.assertTrue(lock.lock())
self.assertTrue(lock.clean)
self.assertTrue(lock.locked)


def test_rmlinkError(self):
"""
An exception raised by L{rmlink} other than C{ENOENT} is passed up
to the caller of L{FilesystemLock.lock}.
"""
def fakeRmlink(name):
raise OSError(errno.ENOSYS, None)
self.patch(lockfile, 'rmlink', fakeRmlink)

def fakeKill(pid, signal):
if signal != 0:
raise OSError(errno.EPERM, None)
if pid == 43125:
raise OSError(errno.ESRCH, None)
self.patch(lockfile, 'kill', fakeKill)

lockf = self.mktemp()

# Make it appear locked so it has to use readlink
lockfile.symlink(str(43125), lockf)

lock = lockfile.FilesystemLock(lockf)
exc = self.assertRaises(OSError, lock.lock)
self.assertEqual(exc.errno, errno.ENOSYS)
self.assertFalse(lock.locked)


def test_killError(self):
"""
If L{kill} raises an exception other than L{OSError} with errno set to
C{ESRCH}, the exception is passed up to the caller of
L{FilesystemLock.lock}.
"""
def fakeKill(pid, signal):
raise OSError(errno.EPERM, None)
self.patch(lockfile, 'kill', fakeKill)

lockf = self.mktemp()

# Make it appear locked so it has to use readlink
lockfile.symlink(str(43125), lockf)

lock = lockfile.FilesystemLock(lockf)
exc = self.assertRaises(OSError, lock.lock)
self.assertEqual(exc.errno, errno.EPERM)
self.assertFalse(lock.locked)


def test_unlockOther(self):
"""
L{FilesystemLock.unlock} raises L{ValueError} if called for a lock
which is held by a different process.
"""
lockf = self.mktemp()
lockfile.symlink(str(os.getpid() + 1), lockf)
lock = lockfile.FilesystemLock(lockf)
self.assertRaises(ValueError, lock.unlock)


def test_isLocked(self):
"""
L{isLocked} returns C{True} if the named lock is currently locked,
C{False} otherwise.
"""
lockf = self.mktemp()
self.assertFalse(lockfile.isLocked(lockf))
lock = lockfile.FilesystemLock(lockf)
self.assertTrue(lock.lock())
self.assertTrue(lockfile.isLocked(lockf))
lock.unlock()
self.assertFalse(lockfile.isLocked(lockf))