Current File : //usr/lib/python3/dist-packages/twisted/internet/test/test_posixprocess.py
# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.
"""
Tests for POSIX-based L{IReactorProcess} implementations.
"""
import errno
import os
import sys
from typing import Optional
platformSkip: Optional[str]
try:
import fcntl
except ImportError:
platformSkip = "non-POSIX platform"
else:
from twisted.internet import process
platformSkip = None
from twisted.trial.unittest import TestCase
class FakeFile:
"""
A dummy file object which records when it is closed.
"""
def __init__(self, testcase, fd):
self.testcase = testcase
self.fd = fd
def close(self):
self.testcase._files.remove(self.fd)
def __enter__(self):
return self
def __exit__(self, exc_type, exc_value, traceback):
self.close()
class FakeResourceModule:
"""
Fake version of L{resource} which hard-codes a particular rlimit for maximum
open files.
@ivar _limit: The value to return for the hard limit of number of open files.
"""
RLIMIT_NOFILE = 1
def __init__(self, limit):
self._limit = limit
def getrlimit(self, no):
"""
A fake of L{resource.getrlimit} which returns a pre-determined result.
"""
if no == self.RLIMIT_NOFILE:
return [0, self._limit]
return [123, 456]
class FDDetectorTests(TestCase):
"""
Tests for _FDDetector class in twisted.internet.process, which detects
which function to drop in place for the _listOpenFDs method.
@ivar devfs: A flag indicating whether the filesystem fake will indicate
that /dev/fd exists.
@ivar accurateDevFDResults: A flag indicating whether the /dev/fd fake
returns accurate open file information.
@ivar procfs: A flag indicating whether the filesystem fake will indicate
that /proc/<pid>/fd exists.
"""
skip = platformSkip
devfs = False
accurateDevFDResults = False
procfs = False
def getpid(self):
"""
Fake os.getpid, always return the same thing
"""
return 123
def listdir(self, arg):
"""
Fake os.listdir, depending on what mode we're in to simulate behaviour.
@param arg: the directory to list
"""
accurate = map(str, self._files)
if self.procfs and arg == ("/proc/%d/fd" % (self.getpid(),)):
return accurate
if self.devfs and arg == "/dev/fd":
if self.accurateDevFDResults:
return accurate
return ["0", "1", "2"]
raise OSError()
def openfile(self, fname, mode):
"""
This is a mock for L{open}. It keeps track of opened files so extra
descriptors can be returned from the mock for L{os.listdir} when used on
one of the list-of-filedescriptors directories.
A L{FakeFile} is returned which can be closed to remove the new
descriptor from the open list.
"""
# Find the smallest unused file descriptor and give it to the new file.
f = FakeFile(self, min(set(range(1024)) - set(self._files)))
self._files.append(f.fd)
return f
def hideResourceModule(self):
"""
Make the L{resource} module unimportable for the remainder of the
current test method.
"""
sys.modules["resource"] = None
def revealResourceModule(self, limit):
"""
Make a L{FakeResourceModule} instance importable at the L{resource}
name.
@param limit: The value which will be returned for the hard limit of
number of open files by the fake resource module's C{getrlimit}
function.
"""
sys.modules["resource"] = FakeResourceModule(limit)
def replaceResourceModule(self, value):
"""
Restore the original resource module to L{sys.modules}.
"""
if value is None:
try:
del sys.modules["resource"]
except KeyError:
pass
else:
sys.modules["resource"] = value
def setUp(self):
"""
Set up the tests, giving ourselves a detector object to play with and
setting up its testable knobs to refer to our mocked versions.
"""
self.detector = process._FDDetector()
self.detector.listdir = self.listdir
self.detector.getpid = self.getpid
self.detector.openfile = self.openfile
self._files = [0, 1, 2]
self.addCleanup(self.replaceResourceModule, sys.modules.get("resource"))
def test_selectFirstWorking(self):
"""
L{FDDetector._getImplementation} returns the first method from its
C{_implementations} list which returns results which reflect a newly
opened file descriptor.
"""
def failWithException():
raise ValueError("This does not work")
def failWithWrongResults():
return [0, 1, 2]
def correct():
return self._files[:]
self.detector._implementations = [
failWithException,
failWithWrongResults,
correct,
]
self.assertIs(correct, self.detector._getImplementation())
def test_selectLast(self):
"""
L{FDDetector._getImplementation} returns the last method from its
C{_implementations} list if none of the implementations manage to return
results which reflect a newly opened file descriptor.
"""
def failWithWrongResults():
return [3, 5, 9]
def failWithOtherWrongResults():
return [0, 1, 2]
self.detector._implementations = [
failWithWrongResults,
failWithOtherWrongResults,
]
self.assertIs(failWithOtherWrongResults, self.detector._getImplementation())
def test_identityOfListOpenFDsChanges(self):
"""
Check that the identity of _listOpenFDs changes after running
_listOpenFDs the first time, but not after the second time it's run.
In other words, check that the monkey patching actually works.
"""
# Create a new instance
detector = process._FDDetector()
first = detector._listOpenFDs.__name__
detector._listOpenFDs()
second = detector._listOpenFDs.__name__
detector._listOpenFDs()
third = detector._listOpenFDs.__name__
self.assertNotEqual(first, second)
self.assertEqual(second, third)
def test_devFDImplementation(self):
"""
L{_FDDetector._devFDImplementation} raises L{OSError} if there is no
I{/dev/fd} directory, otherwise it returns the basenames of its children
interpreted as integers.
"""
self.devfs = False
self.assertRaises(OSError, self.detector._devFDImplementation)
self.devfs = True
self.accurateDevFDResults = False
self.assertEqual([0, 1, 2], self.detector._devFDImplementation())
def test_procFDImplementation(self):
"""
L{_FDDetector._procFDImplementation} raises L{OSError} if there is no
I{/proc/<pid>/fd} directory, otherwise it returns the basenames of its
children interpreted as integers.
"""
self.procfs = False
self.assertRaises(OSError, self.detector._procFDImplementation)
self.procfs = True
self.assertEqual([0, 1, 2], self.detector._procFDImplementation())
def test_resourceFDImplementation(self):
"""
L{_FDDetector._fallbackFDImplementation} uses the L{resource} module if
it is available, returning a range of integers from 0 to the
minimum of C{1024} and the hard I{NOFILE} limit.
"""
# When the resource module is here, use its value.
self.revealResourceModule(512)
self.assertEqual(
list(range(512)), list(self.detector._fallbackFDImplementation())
)
# But limit its value to the arbitrarily selected value 1024.
self.revealResourceModule(2048)
self.assertEqual(
list(range(1024)), list(self.detector._fallbackFDImplementation())
)
def test_fallbackFDImplementation(self):
"""
L{_FDDetector._fallbackFDImplementation}, the implementation of last
resort, succeeds with a fixed range of integers from 0 to 1024 when the
L{resource} module is not importable.
"""
self.hideResourceModule()
self.assertEqual(
list(range(1024)), list(self.detector._fallbackFDImplementation())
)
class FileDescriptorTests(TestCase):
"""
Tests for L{twisted.internet.process._listOpenFDs}
"""
skip = platformSkip
def test_openFDs(self):
"""
File descriptors returned by L{_listOpenFDs} are mostly open.
This test assumes that zero-legth writes fail with EBADF on closed
file descriptors.
"""
for fd in process._listOpenFDs():
try:
fcntl.fcntl(fd, fcntl.F_GETFL)
except OSError as err:
self.assertEqual(
errno.EBADF,
err.errno,
"fcntl(%d, F_GETFL) failed with unexpected errno %d"
% (fd, err.errno),
)
def test_expectedFDs(self):
"""
L{_listOpenFDs} lists expected file descriptors.
"""
# This is a tricky test. A priori, there is no way to know what file
# descriptors are open now, so there is no way to know what _listOpenFDs
# should return. Work around this by creating some new file descriptors
# which we can know the state of and then just making assertions about
# their presence or absence in the result.
# Expect a file we just opened to be listed.
f = open(os.devnull)
openfds = process._listOpenFDs()
self.assertIn(f.fileno(), openfds)
# Expect a file we just closed not to be listed - with a caveat. The
# implementation may need to open a file to discover the result. That
# open file descriptor will be allocated the same number as the one we
# just closed. So, instead, create a hole in the file descriptor space
# to catch that internal descriptor and make the assertion about a
# different closed file descriptor.
# This gets allocated a file descriptor larger than f's, since nothing
# has been closed since we opened f.
fd = os.dup(f.fileno())
# But sanity check that; if it fails the test is invalid.
self.assertTrue(
fd > f.fileno(),
"Expected duplicate file descriptor to be greater than original",
)
try:
# Get rid of the original, creating the hole. The copy should still
# be open, of course.
f.close()
self.assertIn(fd, process._listOpenFDs())
finally:
# Get rid of the copy now
os.close(fd)
# And it should not appear in the result.
self.assertNotIn(fd, process._listOpenFDs())
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