# Copyright (c) Twisted Matrix Laboratories. # See LICENSE for details. """ Tests for L{twisted.python.threadpool} """ from __future__ import division, absolute_import import pickle import time import weakref import gc import threading from twisted.python.compat import range from twisted.trial import unittest from twisted.python import threadpool, threadable, failure, context from twisted._threads import Team, createMemoryWorker class Synchronization(object): failures = 0 def __init__(self, N, waiting): self.N = N self.waiting = waiting self.lock = threading.Lock() self.runs = [] def run(self): # This is the testy part: this is supposed to be invoked # serially from multiple threads. If that is actually the # case, we will never fail to acquire this lock. If it is # *not* the case, we might get here while someone else is # holding the lock. if self.lock.acquire(False): if not len(self.runs) % 5: # Constant selected based on empirical data to maximize the # chance of a quick failure if this code is broken. time.sleep(0.0002) self.lock.release() else: self.failures += 1 # This is just the only way I can think of to wake up the test # method. It doesn't actually have anything to do with the # test. self.lock.acquire() self.runs.append(None) if len(self.runs) == self.N: self.waiting.release() self.lock.release() synchronized = ["run"] threadable.synchronize(Synchronization) class ThreadPoolTests(unittest.SynchronousTestCase): """ Test threadpools. """ def getTimeout(self): """ Return number of seconds to wait before giving up. """ return 5 # Really should be order of magnitude less def _waitForLock(self, lock): items = range(1000000) for i in items: if lock.acquire(False): break time.sleep(1e-5) else: self.fail("A long time passed without succeeding") def test_attributes(self): """ L{ThreadPool.min} and L{ThreadPool.max} are set to the values passed to L{ThreadPool.__init__}. """ pool = threadpool.ThreadPool(12, 22) self.assertEqual(pool.min, 12) self.assertEqual(pool.max, 22) def test_start(self): """ L{ThreadPool.start} creates the minimum number of threads specified. """ pool = threadpool.ThreadPool(0, 5) pool.start() self.addCleanup(pool.stop) self.assertEqual(len(pool.threads), 0) pool = threadpool.ThreadPool(3, 10) self.assertEqual(len(pool.threads), 0) pool.start() self.addCleanup(pool.stop) self.assertEqual(len(pool.threads), 3) def test_adjustingWhenPoolStopped(self): """ L{ThreadPool.adjustPoolsize} only modifies the pool size and does not start new workers while the pool is not running. """ pool = threadpool.ThreadPool(0, 5) pool.start() pool.stop() pool.adjustPoolsize(2) self.assertEqual(len(pool.threads), 0) def test_threadCreationArguments(self): """ Test that creating threads in the threadpool with application-level objects as arguments doesn't results in those objects never being freed, with the thread maintaining a reference to them as long as it exists. """ tp = threadpool.ThreadPool(0, 1) tp.start() self.addCleanup(tp.stop) # Sanity check - no threads should have been started yet. self.assertEqual(tp.threads, []) # Here's our function def worker(arg): pass # weakref needs an object subclass class Dumb(object): pass # And here's the unique object unique = Dumb() workerRef = weakref.ref(worker) uniqueRef = weakref.ref(unique) # Put some work in tp.callInThread(worker, unique) # Add an event to wait completion event = threading.Event() tp.callInThread(event.set) event.wait(self.getTimeout()) del worker del unique gc.collect() self.assertIsNone(uniqueRef()) self.assertIsNone(workerRef()) def test_threadCreationArgumentsCallInThreadWithCallback(self): """ As C{test_threadCreationArguments} above, but for callInThreadWithCallback. """ tp = threadpool.ThreadPool(0, 1) tp.start() self.addCleanup(tp.stop) # Sanity check - no threads should have been started yet. self.assertEqual(tp.threads, []) # this holds references obtained in onResult refdict = {} # name -> ref value onResultWait = threading.Event() onResultDone = threading.Event() resultRef = [] # result callback def onResult(success, result): # Spin the GC, which should now delete worker and unique if it's # not held on to by callInThreadWithCallback after it is complete gc.collect() onResultWait.wait(self.getTimeout()) refdict['workerRef'] = workerRef() refdict['uniqueRef'] = uniqueRef() onResultDone.set() resultRef.append(weakref.ref(result)) # Here's our function def worker(arg, test): return Dumb() # weakref needs an object subclass class Dumb(object): pass # And here's the unique object unique = Dumb() onResultRef = weakref.ref(onResult) workerRef = weakref.ref(worker) uniqueRef = weakref.ref(unique) # Put some work in tp.callInThreadWithCallback(onResult, worker, unique, test=unique) del worker del unique # let onResult collect the refs onResultWait.set() # wait for onResult onResultDone.wait(self.getTimeout()) gc.collect() self.assertIsNone(uniqueRef()) self.assertIsNone(workerRef()) # XXX There's a race right here - has onResult in the worker thread # returned and the locals in _worker holding it and the result been # deleted yet? del onResult gc.collect() self.assertIsNone(onResultRef()) self.assertIsNone(resultRef[0]()) # The callback shouldn't have been able to resolve the references. self.assertEqual(list(refdict.values()), [None, None]) def test_persistence(self): """ Threadpools can be pickled and unpickled, which should preserve the number of threads and other parameters. """ pool = threadpool.ThreadPool(7, 20) self.assertEqual(pool.min, 7) self.assertEqual(pool.max, 20) # check that unpickled threadpool has same number of threads copy = pickle.loads(pickle.dumps(pool)) self.assertEqual(copy.min, 7) self.assertEqual(copy.max, 20) def _threadpoolTest(self, method): """ Test synchronization of calls made with C{method}, which should be one of the mechanisms of the threadpool to execute work in threads. """ # This is a schizophrenic test: it seems to be trying to test # both the callInThread()/dispatch() behavior of the ThreadPool as well # as the serialization behavior of threadable.synchronize(). It # would probably make more sense as two much simpler tests. N = 10 tp = threadpool.ThreadPool() tp.start() self.addCleanup(tp.stop) waiting = threading.Lock() waiting.acquire() actor = Synchronization(N, waiting) for i in range(N): method(tp, actor) self._waitForLock(waiting) self.assertFalse( actor.failures, "run() re-entered {} times".format(actor.failures)) def test_callInThread(self): """ Call C{_threadpoolTest} with C{callInThread}. """ return self._threadpoolTest( lambda tp, actor: tp.callInThread(actor.run)) def test_callInThreadException(self): """ L{ThreadPool.callInThread} logs exceptions raised by the callable it is passed. """ class NewError(Exception): pass def raiseError(): raise NewError() tp = threadpool.ThreadPool(0, 1) tp.callInThread(raiseError) tp.start() tp.stop() errors = self.flushLoggedErrors(NewError) self.assertEqual(len(errors), 1) def test_callInThreadWithCallback(self): """ L{ThreadPool.callInThreadWithCallback} calls C{onResult} with a two-tuple of C{(True, result)} where C{result} is the value returned by the callable supplied. """ waiter = threading.Lock() waiter.acquire() results = [] def onResult(success, result): waiter.release() results.append(success) results.append(result) tp = threadpool.ThreadPool(0, 1) tp.callInThreadWithCallback(onResult, lambda: "test") tp.start() try: self._waitForLock(waiter) finally: tp.stop() self.assertTrue(results[0]) self.assertEqual(results[1], "test") def test_callInThreadWithCallbackExceptionInCallback(self): """ L{ThreadPool.callInThreadWithCallback} calls C{onResult} with a two-tuple of C{(False, failure)} where C{failure} represents the exception raised by the callable supplied. """ class NewError(Exception): pass def raiseError(): raise NewError() waiter = threading.Lock() waiter.acquire() results = [] def onResult(success, result): waiter.release() results.append(success) results.append(result) tp = threadpool.ThreadPool(0, 1) tp.callInThreadWithCallback(onResult, raiseError) tp.start() try: self._waitForLock(waiter) finally: tp.stop() self.assertFalse(results[0]) self.assertIsInstance(results[1], failure.Failure) self.assertTrue(issubclass(results[1].type, NewError)) def test_callInThreadWithCallbackExceptionInOnResult(self): """ L{ThreadPool.callInThreadWithCallback} logs the exception raised by C{onResult}. """ class NewError(Exception): pass waiter = threading.Lock() waiter.acquire() results = [] def onResult(success, result): results.append(success) results.append(result) raise NewError() tp = threadpool.ThreadPool(0, 1) tp.callInThreadWithCallback(onResult, lambda: None) tp.callInThread(waiter.release) tp.start() try: self._waitForLock(waiter) finally: tp.stop() errors = self.flushLoggedErrors(NewError) self.assertEqual(len(errors), 1) self.assertTrue(results[0]) self.assertIsNone(results[1]) def test_callbackThread(self): """ L{ThreadPool.callInThreadWithCallback} calls the function it is given and the C{onResult} callback in the same thread. """ threadIds = [] event = threading.Event() def onResult(success, result): threadIds.append(threading.currentThread().ident) event.set() def func(): threadIds.append(threading.currentThread().ident) tp = threadpool.ThreadPool(0, 1) tp.callInThreadWithCallback(onResult, func) tp.start() self.addCleanup(tp.stop) event.wait(self.getTimeout()) self.assertEqual(len(threadIds), 2) self.assertEqual(threadIds[0], threadIds[1]) def test_callbackContext(self): """ The context L{ThreadPool.callInThreadWithCallback} is invoked in is shared by the context the callable and C{onResult} callback are invoked in. """ myctx = context.theContextTracker.currentContext().contexts[-1] myctx['testing'] = 'this must be present' contexts = [] event = threading.Event() def onResult(success, result): ctx = context.theContextTracker.currentContext().contexts[-1] contexts.append(ctx) event.set() def func(): ctx = context.theContextTracker.currentContext().contexts[-1] contexts.append(ctx) tp = threadpool.ThreadPool(0, 1) tp.callInThreadWithCallback(onResult, func) tp.start() self.addCleanup(tp.stop) event.wait(self.getTimeout()) self.assertEqual(len(contexts), 2) self.assertEqual(myctx, contexts[0]) self.assertEqual(myctx, contexts[1]) def test_existingWork(self): """ Work added to the threadpool before its start should be executed once the threadpool is started: this is ensured by trying to release a lock previously acquired. """ waiter = threading.Lock() waiter.acquire() tp = threadpool.ThreadPool(0, 1) tp.callInThread(waiter.release) # Before start() tp.start() try: self._waitForLock(waiter) finally: tp.stop() def test_workerStateTransition(self): """ As the worker receives and completes work, it transitions between the working and waiting states. """ pool = threadpool.ThreadPool(0, 1) pool.start() self.addCleanup(pool.stop) # Sanity check self.assertEqual(pool.workers, 0) self.assertEqual(len(pool.waiters), 0) self.assertEqual(len(pool.working), 0) # Fire up a worker and give it some 'work' threadWorking = threading.Event() threadFinish = threading.Event() def _thread(): threadWorking.set() threadFinish.wait(10) pool.callInThread(_thread) threadWorking.wait(10) self.assertEqual(pool.workers, 1) self.assertEqual(len(pool.waiters), 0) self.assertEqual(len(pool.working), 1) # Finish work, and spin until state changes threadFinish.set() while not len(pool.waiters): time.sleep(0.0005) # Make sure state changed correctly self.assertEqual(len(pool.waiters), 1) self.assertEqual(len(pool.working), 0) class RaceConditionTests(unittest.SynchronousTestCase): def setUp(self): self.threadpool = threadpool.ThreadPool(0, 10) self.event = threading.Event() self.threadpool.start() def done(): self.threadpool.stop() del self.threadpool self.addCleanup(done) def getTimeout(self): """ A reasonable number of seconds to time out. """ return 5 def test_synchronization(self): """ If multiple threads are waiting on an event (via blocking on something in a callable passed to L{threadpool.ThreadPool.callInThread}), and there is spare capacity in the threadpool, sending another callable which will cause those to un-block to L{threadpool.ThreadPool.callInThread} will reliably run that callable and un-block the blocked threads promptly. @note: This is not really a unit test, it is a stress-test. You may need to run it with C{trial -u} to fail reliably if there is a problem. It is very hard to regression-test for this particular bug - one where the thread pool may consider itself as having "enough capacity" when it really needs to spin up a new thread if it possibly can - in a deterministic way, since the bug can only be provoked by subtle race conditions. """ timeout = self.getTimeout() self.threadpool.callInThread(self.event.set) self.event.wait(timeout) self.event.clear() for i in range(3): self.threadpool.callInThread(self.event.wait) self.threadpool.callInThread(self.event.set) self.event.wait(timeout) if not self.event.isSet(): self.event.set() self.fail( "'set' did not run in thread; timed out waiting on 'wait'." ) class MemoryPool(threadpool.ThreadPool): """ A deterministic threadpool that uses in-memory data structures to queue work rather than threads to execute work. """ def __init__(self, coordinator, failTest, newWorker, *args, **kwargs): """ Initialize this L{MemoryPool} with a test case. @param coordinator: a worker used to coordinate work in the L{Team} underlying this threadpool. @type coordinator: L{twisted._threads.IExclusiveWorker} @param failTest: A 1-argument callable taking an exception and raising a test-failure exception. @type failTest: 1-argument callable taking (L{Failure}) and raising L{unittest.FailTest}. @param newWorker: a 0-argument callable that produces a new L{twisted._threads.IWorker} provider on each invocation. @type newWorker: 0-argument callable returning L{twisted._threads.IWorker}. """ self._coordinator = coordinator self._failTest = failTest self._newWorker = newWorker threadpool.ThreadPool.__init__(self, *args, **kwargs) def _pool(self, currentLimit, threadFactory): """ Override testing hook to create a deterministic threadpool. @param currentLimit: A 1-argument callable which returns the current threadpool size limit. @param threadFactory: ignored in this invocation; a 0-argument callable that would produce a thread. @return: a L{Team} backed by the coordinator and worker passed to L{MemoryPool.__init__}. """ def respectLimit(): # The expression in this method copied and pasted from # twisted.threads._pool, which is unfortunately bound up # with lots of actual-threading stuff. stats = team.statistics() if ((stats.busyWorkerCount + stats.idleWorkerCount) >= currentLimit()): return None return self._newWorker() team = Team(coordinator=self._coordinator, createWorker=respectLimit, logException=self._failTest) return team class PoolHelper(object): """ A L{PoolHelper} constructs a L{threadpool.ThreadPool} that doesn't actually use threads, by using the internal interfaces in L{twisted._threads}. @ivar performCoordination: a 0-argument callable that will perform one unit of "coordination" - work involved in delegating work to other threads - and return L{True} if it did any work, L{False} otherwise. @ivar workers: the workers which represent the threads within the pool - the workers other than the coordinator. @type workers: L{list} of 2-tuple of (L{IWorker}, C{workPerformer}) where C{workPerformer} is a 0-argument callable like C{performCoordination}. @ivar threadpool: a modified L{threadpool.ThreadPool} to test. @type threadpool: L{MemoryPool} """ def __init__(self, testCase, *args, **kwargs): """ Create a L{PoolHelper}. @param testCase: a test case attached to this helper. @type args: The arguments passed to a L{threadpool.ThreadPool}. @type kwargs: The arguments passed to a L{threadpool.ThreadPool} """ coordinator, self.performCoordination = createMemoryWorker() self.workers = [] def newWorker(): self.workers.append(createMemoryWorker()) return self.workers[-1][0] self.threadpool = MemoryPool(coordinator, testCase.fail, newWorker, *args, **kwargs) def performAllCoordination(self): """ Perform all currently scheduled "coordination", which is the work involved in delegating work to other threads. """ while self.performCoordination(): pass class MemoryBackedTests(unittest.SynchronousTestCase): """ Tests using L{PoolHelper} to deterministically test properties of the threadpool implementation. """ def test_workBeforeStarting(self): """ If a threadpool is told to do work before starting, then upon starting up, it will start enough workers to handle all of the enqueued work that it's been given. """ helper = PoolHelper(self, 0, 10) n = 5 for x in range(n): helper.threadpool.callInThread(lambda: None) helper.performAllCoordination() self.assertEqual(helper.workers, []) helper.threadpool.start() helper.performAllCoordination() self.assertEqual(len(helper.workers), n) def test_tooMuchWorkBeforeStarting(self): """ If the amount of work before starting exceeds the maximum number of threads allowed to the threadpool, only the maximum count will be started. """ helper = PoolHelper(self, 0, 10) n = 50 for x in range(n): helper.threadpool.callInThread(lambda: None) helper.performAllCoordination() self.assertEqual(helper.workers, []) helper.threadpool.start() helper.performAllCoordination() self.assertEqual(len(helper.workers), helper.threadpool.max)