Mini Shell
# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.
"""
Tests for L{twisted.python.threadpool}
"""
import gc
import pickle
import threading
import time
import weakref
from twisted._threads import Team, createMemoryWorker
from twisted.python import context, failure, threadable, threadpool
from twisted.trial import unittest
class Synchronization:
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:
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:
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, f"run() re-entered {actor.failures} times")
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.current_thread().ident)
event.set()
def func():
threadIds.append(threading.current_thread().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:
"""
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)
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