CasperSecurity
# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.
"""
Tests for L{twisted._threads._threadworker}.
"""
import gc
import weakref
from threading import ThreadError, local
from twisted.trial.unittest import SynchronousTestCase
from .. import AlreadyQuit, LockWorker, ThreadWorker
class FakeQueueEmpty(Exception):
"""
L{FakeQueue}'s C{get} has exhausted the queue.
"""
class WouldDeadlock(Exception):
"""
If this were a real lock, you'd be deadlocked because the lock would be
double-acquired.
"""
class FakeThread:
"""
A fake L{threading.Thread}.
@ivar target: A target function to run.
@type target: L{callable}
@ivar started: Has this thread been started?
@type started: L{bool}
"""
def __init__(self, target):
"""
Create a L{FakeThread} with a target.
"""
self.target = target
self.started = False
def start(self):
"""
Set the "started" flag.
"""
self.started = True
class FakeQueue:
"""
A fake L{Queue} implementing C{put} and C{get}.
@ivar items: A lit of items placed by C{put} but not yet retrieved by
C{get}.
@type items: L{list}
"""
def __init__(self):
"""
Create a L{FakeQueue}.
"""
self.items = []
def put(self, item):
"""
Put an item into the queue for later retrieval by L{FakeQueue.get}.
@param item: any object
"""
self.items.append(item)
def get(self):
"""
Get an item.
@return: an item previously put by C{put}.
"""
if not self.items:
raise FakeQueueEmpty()
return self.items.pop(0)
class FakeLock:
"""
A stand-in for L{threading.Lock}.
@ivar acquired: Whether this lock is presently acquired.
"""
def __init__(self):
"""
Create a lock in the un-acquired state.
"""
self.acquired = False
def acquire(self):
"""
Acquire the lock. Raise an exception if the lock is already acquired.
"""
if self.acquired:
raise WouldDeadlock()
self.acquired = True
def release(self):
"""
Release the lock. Raise an exception if the lock is not presently
acquired.
"""
if not self.acquired:
raise ThreadError()
self.acquired = False
class ThreadWorkerTests(SynchronousTestCase):
"""
Tests for L{ThreadWorker}.
"""
def setUp(self):
"""
Create a worker with fake threads.
"""
self.fakeThreads = []
self.fakeQueue = FakeQueue()
def startThread(target):
newThread = FakeThread(target=target)
newThread.start()
self.fakeThreads.append(newThread)
return newThread
self.worker = ThreadWorker(startThread, self.fakeQueue)
def test_startsThreadAndPerformsWork(self):
"""
L{ThreadWorker} calls its C{createThread} callable to create a thread,
its C{createQueue} callable to create a queue, and then the thread's
target pulls work from that queue.
"""
self.assertEqual(len(self.fakeThreads), 1)
self.assertEqual(self.fakeThreads[0].started, True)
def doIt():
doIt.done = True
doIt.done = False
self.worker.do(doIt)
self.assertEqual(doIt.done, False)
self.assertRaises(FakeQueueEmpty, self.fakeThreads[0].target)
self.assertEqual(doIt.done, True)
def test_quitPreventsFutureCalls(self):
"""
L{ThreadWorker.quit} causes future calls to L{ThreadWorker.do} and
L{ThreadWorker.quit} to raise L{AlreadyQuit}.
"""
self.worker.quit()
self.assertRaises(AlreadyQuit, self.worker.quit)
self.assertRaises(AlreadyQuit, self.worker.do, list)
class LockWorkerTests(SynchronousTestCase):
"""
Tests for L{LockWorker}.
"""
def test_fakeDeadlock(self):
"""
The L{FakeLock} test fixture will alert us if there's a potential
deadlock.
"""
lock = FakeLock()
lock.acquire()
self.assertRaises(WouldDeadlock, lock.acquire)
def test_fakeDoubleRelease(self):
"""
The L{FakeLock} test fixture will alert us if there's a potential
double-release.
"""
lock = FakeLock()
self.assertRaises(ThreadError, lock.release)
lock.acquire()
self.assertEqual(None, lock.release())
self.assertRaises(ThreadError, lock.release)
def test_doExecutesImmediatelyWithLock(self):
"""
L{LockWorker.do} immediately performs the work it's given, while the
lock is acquired.
"""
storage = local()
lock = FakeLock()
worker = LockWorker(lock, storage)
def work():
work.done = True
work.acquired = lock.acquired
work.done = False
worker.do(work)
self.assertEqual(work.done, True)
self.assertEqual(work.acquired, True)
self.assertEqual(lock.acquired, False)
def test_doUnwindsReentrancy(self):
"""
If L{LockWorker.do} is called recursively, it postpones the inner call
until the outer one is complete.
"""
lock = FakeLock()
worker = LockWorker(lock, local())
levels = []
acquired = []
def work():
work.level += 1
levels.append(work.level)
acquired.append(lock.acquired)
if len(levels) < 2:
worker.do(work)
work.level -= 1
work.level = 0
worker.do(work)
self.assertEqual(levels, [1, 1])
self.assertEqual(acquired, [True, True])
def test_quit(self):
"""
L{LockWorker.quit} frees the resources associated with its lock and
causes further calls to C{do} and C{quit} to fail.
"""
lock = FakeLock()
ref = weakref.ref(lock)
worker = LockWorker(lock, local())
lock = None
self.assertIsNot(ref(), None)
worker.quit()
gc.collect()
self.assertIs(ref(), None)
self.assertRaises(AlreadyQuit, worker.quit)
self.assertRaises(AlreadyQuit, worker.do, list)
def test_quitWhileWorking(self):
"""
If L{LockWorker.quit} is invoked during a call to L{LockWorker.do}, all
recursive work scheduled with L{LockWorker.do} will be completed and
the lock will be released.
"""
lock = FakeLock()
ref = weakref.ref(lock)
worker = LockWorker(lock, local())
def phase1():
worker.do(phase2)
worker.quit()
self.assertRaises(AlreadyQuit, worker.do, list)
phase1.complete = True
phase1.complete = False
def phase2():
phase2.complete = True
phase2.acquired = lock.acquired
phase2.complete = False
worker.do(phase1)
self.assertEqual(phase1.complete, True)
self.assertEqual(phase2.complete, True)
self.assertEqual(lock.acquired, False)
lock = None
gc.collect()
self.assertIs(ref(), None)
def test_quitWhileGettingLock(self):
"""
If L{LockWorker.do} is called concurrently with L{LockWorker.quit}, and
C{quit} wins the race before C{do} gets the lock attribute, then
L{AlreadyQuit} will be raised.
"""
class RacyLockWorker(LockWorker):
@property
def _lock(self):
self.quit()
return self.__dict__["_lock"]
@_lock.setter
def _lock(self, value):
self.__dict__["_lock"] = value
worker = RacyLockWorker(FakeLock(), local())
self.assertRaises(AlreadyQuit, worker.do, list)