commit c35b28365412b1a854865fad7b1ce500928c5093 Author: Leonid Evdokimov leon@darkk.net.ru Date: Fri Oct 7 23:13:13 2016 +0300

Add _failing_ scheduler test showing one of #612 deadlock reasons

If the lock has too many waiters then some stack overflow raises RuntimeError and scheduler fails altogether. --- ooni/tests/test_scheduler.py | 35 ++++++++++++++++++++++++++++++++++- 1 file changed, 34 insertions(+), 1 deletion(-)

diff --git a/ooni/tests/test_scheduler.py b/ooni/tests/test_scheduler.py index a9501c0..c8eaf55 100644 --- a/ooni/tests/test_scheduler.py +++ b/ooni/tests/test_scheduler.py @@ -1,9 +1,10 @@ import os +import sys import shutil import random import tempfile

-from twisted.internet import defer +from twisted.internet import reactor, task, defer from twisted.trial import unittest

from ooni.agent.scheduler import ScheduledTask, DidNotRun, FileSystemlockAndMutex @@ -51,8 +52,40 @@ class TestScheduler(unittest.TestCase): self.assertEqual(len(in_file.readlines()), 1)

self.assertEqual(dummy_st.should_run, False) + self.assertFalse(os.path.islink(os.path.join(scheduler_directory, identifier + '.lock'))) shutil.rmtree(scheduler_directory)

+ def test_thundering_herd(self): + lockno = int(os.getenv('TTH_LOCKNO', str(sys.getrecursionlimit() + 16))) + scheduler_directory = tempfile.mkdtemp() + counter = os.path.join(scheduler_directory, 'counter') + class DummyST(ScheduledTask): + @defer.inlineCallbacks + def task(subself): + self.assertTrue(os.path.islink(os.path.join(scheduler_directory, subself.identifier + '.lock'))) + with open(counter, 'w+') as fd: + data = fd.read() + fd.seek(0) + if not data: + fd.write('1') + yield task.deferLater(reactor, 1, lambda: 42) + else: + self.assertTrue(False) # should be unreachable due to schedule + identifier = "dummy" + dummy_st = DummyST(schedule='@daily', identifier=identifier, scheduler_directory=scheduler_directory) + dl = defer.DeferredList([dummy_st.run() for i in xrange(lockno)], consumeErrors=True) + @dl.addBoth + def so_what(results): + self.assertFalse(os.path.islink(os.path.join(scheduler_directory, identifier + '.lock'))) + self.assertEqual(results[0], (True, None)) # do not expect to get `42` here + for okflag, ex in results[1:]: + self.assertEqual(okflag, False) + ex.trap(DidNotRun) + self.assertEqual(dummy_st.should_run, False) + with open(counter, 'r') as fd: + self.assertEqual(fd.read(), '1') + shutil.rmtree(scheduler_directory) + return dl

@defer.inlineCallbacks def test_filesystem_lock_and_mutex(self):