def test_deferred_task_cannot_be_cancelled_when_running(self):
# DatabaseTaskAlreadyRunning is raised when attempting to cancel a
# database task that's already running.
service = DatabaseTasksService()
yield service.startService()
try:
ready = Deferred()
d = service.deferTask(reactor.callFromThread, ready.callback, None)
# Wait for the task to begin running.
yield ready
# We have the reactor thread. Even if the task completes its
# status will not be updated until the reactor's next iteration.
self.assertRaises(DatabaseTaskAlreadyRunning, d.cancel)
finally:
yield service.stopService()
def test__cannot_defer_task_when_queue_is_full(self):
service = DatabaseTasksService(0)
service.startService()
try:
event = threading.Event()
service.addTask(event.wait)
try:
self.assertRaises(QueueOverflow,
lambda: service.deferTask(noop).wait(30))
finally:
event.set()
finally:
service.stopService()
def test_sync_task_fires_with_service(self):
service = DatabaseTasksService()
service.startService()
try:
self.assertThat(service.syncTask().wait(30), Is(service))
finally:
service.stopService()
def test__init(self):
service = DatabaseTasksService()
self.assertThat(
service,
MatchesStructure(
# The queue does not permit anything to go in it.
queue=MatchesAll(
IsInstance(DeferredQueue),
MatchesStructure.byEquality(size=0, backlog=1),
first_only=True,
), ))
def test_sync_task_can_be_cancelled_when_enqueued(self):
things = [] # This will NOT be populated by tasks.
service = DatabaseTasksService()
yield service.startService()
try:
event = threading.Event()
service.deferTask(event.wait)
service.syncTask().cancel()
finally:
event.set()
yield service.stopService()
self.assertThat(things, Equals([]))
def test__task_is_executed_in_other_thread(self):
get_thread_ident = lambda: threading.currentThread().ident
service = DatabaseTasksService()
service.startService()
try:
ident_from_task = service.deferTask(get_thread_ident).wait(30)
ident_from_here = get_thread_ident()
self.expectThat(ident_from_task, IsInstance(int, int))
self.expectThat(ident_from_task, Not(Equals(ident_from_here)))
finally:
service.stopService()
def test_task_can_access_database_from_other_thread(self):
@transactional
def database_task():
# Merely being here means we've accessed the database.
return sentinel.beenhere
service = DatabaseTasksService()
service.startService()
try:
result = service.deferTask(database_task).wait(30)
self.assertThat(result, Is(sentinel.beenhere))
finally:
service.stopService()
def test__init(self):
limit = random.randint(1, 1000)
service = DatabaseTasksService(limit)
self.assertThat(
service,
MatchesStructure(
# Our requested limit is saved.
limit=Equals(limit),
# The queue does not permit anything to go in it.
queue=MatchesAll(
IsInstance(DeferredQueue),
MatchesStructure.byEquality(size=0, backlog=1),
first_only=True,
),
))
def test__failure_in_task_is_logged(self):
logger = self.useFixture(TwistedLoggerFixture())
service = DatabaseTasksService()
service.startService()
try:
service.addTask(lambda: 0 / 0)
finally:
service.stopService()
self.assertDocTestMatches(
"""\
...Unhandled failure in database task.
Traceback (most recent call last):
...
builtins.ZeroDivisionError: ...
""", logger.output)
def test__tasks_are_all_run_before_shutdown_completes(self):
service = DatabaseTasksService()
service.startService()
try:
queue = service.queue
event = threading.Event()
count = random.randint(20, 40)
for _ in range(count):
service.addTask(event.wait)
# The queue has `count` tasks (or `count - 1` tasks; the first may
# have already been pulled off the queue) still pending.
self.assertThat(queue.pending,
MatchesAny(HasLength(count), HasLength(count - 1)))
finally:
event.set()
service.stopService()
# The queue is empty and nothing is waiting.
self.assertThat(queue,
MatchesStructure.byEquality(waiting=[], pending=[]))
def test_arguments_are_passed_through_to_task(self):
def return_args(*args, **kwargs):
return sentinel.here, args, kwargs
service = DatabaseTasksService()
service.startService()
try:
result = service.deferTask(
return_args, sentinel.arg, kw=sentinel.kw
).wait(30)
self.assertThat(
result,
Equals((sentinel.here, (sentinel.arg,), {"kw": sentinel.kw})),
)
finally:
service.stopService()
def test__startup_creates_queue_with_previously_defined(self):
service = DatabaseTasksService()
service.startService()
try:
self.assertThat(
service,
MatchesStructure(queue=MatchesAll(
IsInstance(DeferredQueue),
MatchesStructure.byEquality(backlog=1),
first_only=True,
), ))
finally:
service.stopService()
def test__startup_creates_queue_with_previously_defined_limit(self):
limit = random.randint(1, 1000)
service = DatabaseTasksService(limit)
service.startService()
try:
self.assertThat(
service,
MatchesStructure(
# The queue has been set to the `limit` size, and only one
# thing is allowed to wait on the queue.
queue=MatchesAll(
IsInstance(DeferredQueue),
MatchesStructure.byEquality(size=limit, backlog=1),
first_only=True,
), ))
finally:
service.stopService()
def test_cannot_add_task_to_stopped_service(self):
service = DatabaseTasksService()
service.startService()
service.stopService()
self.assertRaises(QueueOverflow, service.addTask, noop)
def test_failure_in_added_task_does_not_crash_service(self):
things = [] # This will be populated by tasks.
exception_type = factory.make_exception_type()
def be_bad():
raise exception_type("I'm bad, so bad.")
service = DatabaseTasksService()
service.startService()
try:
service.addTask(things.append, 1)
service.addTask(be_bad)
service.addTask(things.append, 2)
finally:
service.stopService()
self.assertThat(things, Equals([1, 2]))
def test_failure_in_deferred_task_does_not_crash_service(self):
things = [] # This will be populated by tasks.
exception_type = factory.make_exception_type()
def be_bad():
raise exception_type("I'm being very naughty.")
service = DatabaseTasksService()
service.startService()
try:
service.deferTask(things.append, 1).wait(30)
self.assertRaises(
exception_type, service.deferTask(be_bad).wait, 30
)
service.deferTask(things.append, 2).wait(30)
finally:
service.stopService()
self.assertThat(things, Equals([1, 2]))
def test__init_default_limit(self):
service = DatabaseTasksService()
self.assertThat(service.limit, Equals(100))
