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from unittest import TestCase
import time
import threading
from dogpile.core import Lock, NeedRegenerationException
from dogpile.core.nameregistry import NameRegistry
import contextlib
import math
import logging
log = logging.getLogger(__name__)
class ConcurrencyTest(TestCase):
# expiretime, time to create, num usages, time spend using, delay btw usage
_assertion_lock = threading.Lock()
def test_quick(self):
self._test_multi(
10, 2, .5, 50, .05, .1,
)
def test_slow(self):
self._test_multi(
10, 5, 2, 50, .1, .1,
)
def test_return_while_in_progress(self):
self._test_multi(
10, 5, 2, 50, 1, .1
)
def test_get_value_plus_created_long_create(self):
self._test_multi(
10, 2, 2.5, 50, .05, .1,
)
def test_get_value_plus_created_registry_unsafe_cache(self):
self._test_multi(
10, 1, .6, 100, .05, .1,
cache_expire_time='unsafe'
)
def test_get_value_plus_created_registry_safe_cache_quick(self):
self._test_multi(
10, 2, .5, 50, .05, .1,
cache_expire_time='safe'
)
def test_get_value_plus_created_registry_safe_cache_slow(self):
self._test_multi(
10, 5, 2, 50, .1, .1,
cache_expire_time='safe'
)
def _assert_synchronized(self):
acq = self._assertion_lock.acquire(False)
assert acq, "Could not acquire"
@contextlib.contextmanager
def go():
try:
yield {}
except:
raise
finally:
self._assertion_lock.release()
return go()
def _assert_log(self, cond, msg, *args):
if cond:
log.debug(msg, *args)
else:
log.error("Assertion failed: " + msg, *args)
assert False, msg % args
def _test_multi(self, num_threads,
expiretime,
creation_time,
num_usages,
usage_time,
delay_time,
cache_expire_time=None):
mutex = threading.Lock()
unsafe_cache = False
if cache_expire_time:
if cache_expire_time == 'unsafe':
unsafe_cache = True
cache_expire_time = expiretime * .8
elif cache_expire_time == 'safe':
cache_expire_time = (expiretime + creation_time) * 1.1
else:
assert False, cache_expire_time
log.info("Cache expire time: %s", cache_expire_time)
effective_expiretime = min(cache_expire_time, expiretime)
else:
effective_expiretime = expiretime
effective_creation_time = creation_time
max_stale = (effective_expiretime + effective_creation_time +
usage_time + delay_time) * 1.1
the_resource = []
slow_waiters = [0]
failures = [0]
def create_resource():
with self._assert_synchronized():
log.debug("creating resource, will take %f sec" % creation_time)
time.sleep(creation_time)
the_resource.append(time.time())
value = the_resource[-1]
log.debug("finished creating resource")
return value, time.time()
def get_value():
if not the_resource:
raise NeedRegenerationException()
if cache_expire_time:
if time.time() - the_resource[-1] > cache_expire_time:
# should never hit a cache invalidation
# if we've set expiretime below the cache
# expire time (assuming a cache which
# honors this).
self._assert_log(
cache_expire_time < expiretime,
"Cache expiration hit, cache "
"expire time %s, expiretime %s",
cache_expire_time,
expiretime,
)
raise NeedRegenerationException()
return the_resource[-1], the_resource[-1]
def use_dogpile():
try:
for i in range(num_usages):
now = time.time()
with Lock(mutex, create_resource, get_value, expiretime) as value:
waited = time.time() - now
if waited > .01:
slow_waiters[0] += 1
check_value(value, waited)
time.sleep(usage_time)
time.sleep(delay_time)
except:
log.error("thread failed", exc_info=True)
failures[0] += 1
def check_value(value, waited):
assert value
# time since the current resource was
# created
time_since_create = time.time() - value
self._assert_log(
time_since_create < max_stale,
"Time since create %.4f max stale time %s, "
"total waited %s",
time_since_create, max_stale,
slow_waiters[0]
)
started_at = time.time()
threads = []
for i in range(num_threads):
t = threading.Thread(target=use_dogpile)
t.start()
threads.append(t)
for t in threads:
t.join()
actual_run_time = time.time() - started_at
# time spent starts with num usages * time per usage, with a 10% fudge
expected_run_time = (num_usages * (usage_time + delay_time)) * 1.1
expected_generations = math.ceil(expected_run_time / effective_expiretime)
if unsafe_cache:
expected_slow_waiters = expected_generations * num_threads
else:
expected_slow_waiters = expected_generations + num_threads - 1
# time spent also increments by one wait period in the beginning...
expected_run_time += effective_creation_time
# and a fudged version of the periodic waiting time anticipated
# for a single thread...
expected_run_time += (expected_slow_waiters * effective_creation_time) / num_threads
expected_run_time *= 1.1
log.info("Test Summary")
log.info("num threads: %s; expiretime: %s; creation_time: %s; "
"num_usages: %s; "
"usage_time: %s; delay_time: %s",
num_threads, expiretime, creation_time, num_usages,
usage_time, delay_time
)
log.info("cache expire time: %s; unsafe cache: %s",
cache_expire_time, unsafe_cache)
log.info("Estimated run time %.2f actual run time %.2f",
expected_run_time, actual_run_time)
log.info("Effective expiretime (min(cache_exp_time, exptime)) %s",
effective_expiretime)
log.info("Expected slow waits %s, Total slow waits %s",
expected_slow_waiters, slow_waiters[0])
log.info("Total generations %s Max generations expected %s" % (
len(the_resource), expected_generations
))
assert not failures[0], "%s failures occurred" % failures[0]
assert actual_run_time <= expected_run_time
assert slow_waiters[0] <= expected_slow_waiters, \
"Number of slow waiters %s exceeds expected slow waiters %s" % (
slow_waiters[0],
expected_slow_waiters
)
assert len(the_resource) <= expected_generations,\
"Number of resource generations %d exceeded "\
"expected %d" % (len(the_resource),
expected_generations)
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