Python tornado.gen.Task() Examples

def test_stack_context_leak_exception(self):
        # same as previous, but with a function that exits with an exception
        @gen.engine
        def inner(callback):
            yield gen.Task(self.io_loop.add_callback)
            1 / 0

        @gen.engine
        def outer():
            for i in range(10):
                try:
                    yield gen.Task(inner)
                except ZeroDivisionError:
                    pass
            stack_increase = len(stack_context._state.contexts) - initial_stack_depth
            self.assertTrue(stack_increase <= 2)
            self.stop()
        initial_stack_depth = len(stack_context._state.contexts)
        self.run_gen(outer) 

def test_swallow_context_exception(self):
        # Test exception handling: exceptions thrown into the stack context
        # can be caught and ignored.
        @gen.coroutine
        def f2():
            (yield gen.Callback(1))()
            yield gen.Wait(1)
            self.io_loop.add_callback(lambda: 1 / 0)
            try:
                yield gen.Task(self.io_loop.add_timeout,
                               self.io_loop.time() + 10)
            except ZeroDivisionError:
                raise gen.Return(42)

        result = yield f2()
        self.assertEqual(result, 42)
        self.finished = True 

def test_task_refcounting(self):
        # On CPython, tasks and their arguments should be released immediately
        # without waiting for garbage collection.
        @gen.engine
        def f():
            class Foo(object):
                pass
            arg = Foo()
            self.arg_ref = weakref.ref(arg)
            task = gen.Task(self.io_loop.add_callback, arg=arg)
            self.task_ref = weakref.ref(task)
            yield task
            self.stop()

        self.run_gen(f)
        self.assertIs(self.arg_ref(), None)
        self.assertIs(self.task_ref(), None) 

def test_stack_context_leak_exception(self):
        # same as previous, but with a function that exits with an exception
        @gen.engine
        def inner(callback):
            yield gen.Task(self.io_loop.add_callback)
            1 / 0

        @gen.engine
        def outer():
            for i in range(10):
                try:
                    yield gen.Task(inner)
                except ZeroDivisionError:
                    pass
            stack_increase = len(stack_context._state.contexts) - initial_stack_depth
            self.assertTrue(stack_increase <= 2)
            self.stop()
        initial_stack_depth = len(stack_context._state.contexts)
        self.run_gen(outer) 

def test_future_traceback(self):
        @return_future
        @gen.engine
        def f(callback):
            yield gen.Task(self.io_loop.add_callback)
            try:
                1 / 0
            except ZeroDivisionError:
                self.expected_frame = traceback.extract_tb(
                    sys.exc_info()[2], limit=1)[0]
                raise
        try:
            yield f()
            self.fail("didn't get expected exception")
        except ZeroDivisionError:
            tb = traceback.extract_tb(sys.exc_info()[2])
            self.assertIn(self.expected_frame, tb)

# The following series of classes demonstrate and test various styles
# of use, with and without generators and futures. 

def test_body_size_override_reset(self):
        # The max_body_size override is reset between requests.
        stream = IOStream(socket.socket())
        try:
            yield stream.connect(('127.0.0.1', self.get_http_port()))
            # Use a raw stream so we can make sure it's all on one connection.
            stream.write(b'PUT /streaming?expected_size=10240 HTTP/1.1\r\n'
                         b'Content-Length: 10240\r\n\r\n')
            stream.write(b'a' * 10240)
            headers, response = yield gen.Task(read_stream_body, stream)
            self.assertEqual(response, b'10240')
            # Without the ?expected_size parameter, we get the old default value
            stream.write(b'PUT /streaming HTTP/1.1\r\n'
                         b'Content-Length: 10240\r\n\r\n')
            with ExpectLog(gen_log, '.*Content-Length too long'):
                data = yield stream.read_until_close()
            self.assertEqual(data, b'')
        finally:
            stream.close() 

def test_async_await_mixed_multi_native_yieldpoint(self):
        namespace = exec_test(globals(), locals(), """
        async def f1():
            await gen.Task(self.io_loop.add_callback)
            return 42
        """)

        @gen.coroutine
        def f2():
            yield gen.Task(self.io_loop.add_callback)
            raise gen.Return(43)

        f2(callback=(yield gen.Callback('cb')))
        results = yield [namespace['f1'](), gen.Wait('cb')]
        self.assertEqual(results, [42, 43])
        self.finished = True 

def test_run_with_stack_context(self):
        @gen.coroutine
        def f1():
            self.assertEqual(self.active_contexts, ['c1'])
            yield run_with_stack_context(
                StackContext(functools.partial(self.context, 'c2')),
                f2)
            self.assertEqual(self.active_contexts, ['c1'])

        @gen.coroutine
        def f2():
            self.assertEqual(self.active_contexts, ['c1', 'c2'])
            yield gen.Task(self.io_loop.add_callback)
            self.assertEqual(self.active_contexts, ['c1', 'c2'])

        self.assertEqual(self.active_contexts, [])
        yield run_with_stack_context(
            StackContext(functools.partial(self.context, 'c1')),
            f1)
        self.assertEqual(self.active_contexts, []) 

def test_task_refcounting(self):
        # On CPython, tasks and their arguments should be released immediately
        # without waiting for garbage collection.
        @gen.engine
        def f():
            class Foo(object):
                pass
            arg = Foo()
            self.arg_ref = weakref.ref(arg)
            task = gen.Task(self.io_loop.add_callback, arg=arg)
            self.task_ref = weakref.ref(task)
            yield task
            self.stop()

        self.run_gen(f)
        self.assertIs(self.arg_ref(), None)
        self.assertIs(self.task_ref(), None) 

def test_timeout(self):
        # Set a short timeout and exceed it.
        @gen_test(timeout=0.1)
        def test(self):
            yield gen.Task(self.io_loop.add_timeout, self.io_loop.time() + 1)

        # This can't use assertRaises because we need to inspect the
        # exc_info triple (and not just the exception object)
        try:
            test(self)
            self.fail("did not get expected exception")
        except ioloop.TimeoutError:
            # The stack trace should blame the add_timeout line, not just
            # unrelated IOLoop/testing internals.
            self.assertIn(
                "gen.Task(self.io_loop.add_timeout, self.io_loop.time() + 1)",
                traceback.format_exc())

        self.finished = True 

def test_stack_context_leak(self):
        # regression test: repeated invocations of a gen-based
        # function should not result in accumulated stack_contexts
        def _stack_depth():
            head = stack_context._state.contexts[1]
            length = 0

            while head is not None:
                length += 1
                head = head.old_contexts[1]

            return length

        @gen.engine
        def inner(callback):
            yield gen.Task(self.io_loop.add_callback)
            callback()

        @gen.engine
        def outer():
            for i in range(10):
                yield gen.Task(inner)

            stack_increase = _stack_depth() - initial_stack_depth
            self.assertTrue(stack_increase <= 2)
            self.stop()
        initial_stack_depth = _stack_depth()
        self.run_gen(outer) 

def test_arguments(self):
        @gen.engine
        def f():
            (yield gen.Callback("noargs"))()
            self.assertEqual((yield gen.Wait("noargs")), None)
            (yield gen.Callback("1arg"))(42)
            self.assertEqual((yield gen.Wait("1arg")), 42)

            (yield gen.Callback("kwargs"))(value=42)
            result = yield gen.Wait("kwargs")
            self.assertTrue(isinstance(result, gen.Arguments))
            self.assertEqual(((), dict(value=42)), result)
            self.assertEqual(dict(value=42), result.kwargs)

            (yield gen.Callback("2args"))(42, 43)
            result = yield gen.Wait("2args")
            self.assertTrue(isinstance(result, gen.Arguments))
            self.assertEqual(((42, 43), {}), result)
            self.assertEqual((42, 43), result.args)

            def task_func(callback):
                callback(None, error="foo")
            result = yield gen.Task(task_func)
            self.assertTrue(isinstance(result, gen.Arguments))
            self.assertEqual(((None,), dict(error="foo")), result)

            self.stop()
        self.run_gen(f) 

def test_async_return(self):
        namespace = exec_test(globals(), locals(), """
        @gen.coroutine
        def f():
            yield gen.Task(self.io_loop.add_callback)
            return 42
        """)
        result = yield namespace['f']()
        self.assertEqual(result, 42)
        self.finished = True 

def test_async_raise_return_value_tuple(self):
        @gen.engine
        def f():
            yield gen.Task(self.io_loop.add_callback)
            raise gen.Return((1, 2))

        with self.assertRaises(gen.ReturnValueIgnoredError):
            self.run_gen(f) 

def test_task_transfer_stack_context(self):
        yield gen.Task(self.function_with_stack_context)
        self.assertEqual(self.named_contexts, []) 

def test_native_coroutine(self):
        namespace = exec_test(globals(), locals(), """
        async def f():
            await gen.Task(self.io_loop.add_callback)
        """)
        self.io_loop.run_sync(namespace['f']) 

def test_async_raise_return_value(self):
        @gen.engine
        def f():
            yield gen.Task(self.io_loop.add_callback)
            raise gen.Return(42)

        with self.assertRaises(gen.ReturnValueIgnoredError):
            self.run_gen(f) 

def test_exception_in_task_phase1(self):
        def fail_task(callback):
            1 / 0

        @gen.engine
        def f():
            try:
                yield gen.Task(fail_task)
                raise Exception("did not get expected exception")
            except ZeroDivisionError:
                self.stop()
        self.run_gen(f) 

def test_timeout(self):
        @gen.coroutine
        def f():
            yield gen.Task(self.io_loop.add_timeout, self.io_loop.time() + 1)
        self.assertRaises(TimeoutError, self.io_loop.run_sync, f, timeout=0.01) 

def test_async_exception(self):
        @gen.coroutine
        def f():
            yield gen.Task(self.io_loop.add_callback)
            1 / 0
        with self.assertRaises(ZeroDivisionError):
            self.io_loop.run_sync(f) 

def test_async_result(self):
        @gen.coroutine
        def f():
            yield gen.Task(self.io_loop.add_callback)
            raise gen.Return(42)
        self.assertEqual(self.io_loop.run_sync(f), 42) 

def get_handlers(self):
        class DecoratedFlowControlHandler(BaseFlowControlHandler):
            @gen.coroutine
            def data_received(self, data):
                with self.in_method('data_received'):
                    yield gen.Task(IOLoop.current().add_callback)
        return [('/', DecoratedFlowControlHandler, dict(test=self))] 

def post(self):
        with self.in_method('post'):
            yield gen.Task(IOLoop.current().add_callback)
        self.write(dict(methods=self.methods)) 

def prepare(self):
        # Note that asynchronous prepare() does not block data_received,
        # so we don't use in_method here.
        self.methods.append('prepare')
        yield gen.Task(IOLoop.current().add_callback) 

def test_early_return_with_data(self):
        stream = self.connect(b"/early_return", connection_close=False)
        stream.write(b"4\r\nasdf\r\n")
        data = yield gen.Task(stream.read_until_close)
        self.assertTrue(data.startswith(b"HTTP/1.1 401")) 

def test_early_return(self):
        stream = self.connect(b"/early_return", connection_close=False)
        data = yield gen.Task(stream.read_until_close)
        self.assertTrue(data.startswith(b"HTTP/1.1 401")) 

def get(self):
        # Ensure that the flush callback is run whether or not there
        # was any output.  The gen.Task and direct yield forms are
        # equivalent.
        yield gen.Task(self.flush)  # "empty" flush, but writes headers
        yield gen.Task(self.flush)  # empty flush
        self.write("o")
        yield self.flush()  # flushes the "o"
        yield self.flush()  # empty flush
        self.finish("k") 

def test_yield_in_with_exception_stack_context(self):
        # As above, but with ExceptionStackContext instead of StackContext.
        @gen.engine
        def f():
            with ExceptionStackContext(lambda t, v, tb: False):
                yield gen.Task(self.io_loop.add_callback)

        with self.assertRaises(StackContextInconsistentError):
            f()
            self.wait() 

def test_with_method_kwargs(self):
        @gen_test
        def test_with_kwargs(self, **kwargs):
            self.assertDictEqual(kwargs, {'test': 'test'})
            yield gen.Task(self.io_loop.add_callback)

        test_with_kwargs(self, test='test')
        self.finished = True 

def test_with_method_args(self):
        @gen_test
        def test_with_args(self, *args):
            self.assertEqual(args, ('test',))
            yield gen.Task(self.io_loop.add_callback)

        test_with_args(self, 'test')
        self.finished = True