PYTHON-5071 Use one event loop for all asyncio tests

[ShaneHarvey]

PYTHON-5071 Use one event loop for all asyncio tests

[NoahStapp]

The PyPy variant failure looks like the same asyncio SSL bug we've been tracking in pypy/pypy#5131. The other failures are all test.asynchronous.test_client.TestClient.test_continuous_network_errors, but it's not clear why this change would cause that failure.

[ShaneHarvey]

I suspect the test_continuous_network_errors errors are a side effect of having too many unopened clients or perhaps too many unawaited SDAM tasks. I removed the logic to reinit the client_context on each test. Let's see if that fixes it.

[ShaneHarvey]

I also fixed an issue in loop management which was causing some tests to encounter RuntimeError: <asyncio.locks.Condition object at 0x1095c2250 [locked]> is bound to a different event loop in asyncTearDown. The fix was make the loop initialization lazy sot hat it gets created on the first async test, instead of in __init__ which gets called at when collecting the tests.

[ShaneHarvey]

My latest commit fixes this pytest-asyncio error when tearing down the async test suite:

ERROR test/test_write_concern.py::TestWriteConcern::test_invalid - DeprecationWarning: pytest-asyncio detected an unclosed event loop when tearing down the event_loop
fixture: <_UnixSelectorEventLoop running=False closed=False debug=False>
pytest-asyncio will close the event loop for you, but future versions of the
library will no longer do so. In order to ensure compatibility with future
versions, please make sure that:
    1. Any custom "event_loop" fixture properly closes the loop after yielding it
    2. The scopes of your custom "event_loop" fixtures do not overlap
    3. Your code does not modify the event loop in async fixtures or tests

To fix it, we now use scope=session in conftest and bind to pytest's global event loop. This way pytest manages creating and destroying the loop.

[ShaneHarvey]

I went back to package scope because I believe that's actually what we want. With "session" scope, the async teardown doesn't happen until after all the sync tests run which causes problems because the client has been paused that whole time. This actually highlights a problem with async MongoClient, if the loop is paused for a while and then resumed the client's SDAM state will be out of date. This is similar to the sigstop/sigcont behavior.

[NoahStapp]

Is this supposed to be get_loop instead?

[blink1073]

No, this is the correct method to call within an async function.

[NoahStapp]

Good catch. I think we still have a loop mismatch here, although I might be misunderstanding: this will use the loop pytest creates for our package-scoped test_setup_and_teardown fixture. Then, our first async testcase will create its own separate loop that will be used for each test. So our async_client_context will be on one pytest-managed loop, and all of our test cases will be on one self-managed loop created by get_loop.

[NoahStapp]

Our pyproject.toml also sets the default loop_scope to be session instead of package FYI.

[ShaneHarvey]

Either one is fine because get_loop calls get_running_loop first but I updated to use get_loop to be more consistent.

[ShaneHarvey]

Attempting to use "package" in pyproject.toml results in this error:

____________________________________________________ ERROR at setup of TestCommon.test_mongo_client ____________________________________________________
file /Users/shane/git/mongo-python-driver/test/asynchronous/test_common.py, line 135
      async def test_mongo_client(self):
          pair = await async_client_context.pair
          m = await self.async_rs_or_single_client(w=0)
          coll = m.pymongo_test.write_concern_test
          await coll.drop()
          doc = {"_id": ObjectId()}
          await coll.insert_one(doc)
          self.assertTrue(await coll.insert_one(doc))
          coll = coll.with_options(write_concern=WriteConcern(w=1))
          with self.assertRaises(OperationFailure):
              await coll.insert_one(doc)

          m = await self.async_rs_or_single_client()
          coll = m.pymongo_test.write_concern_test
          new_coll = coll.with_options(write_concern=WriteConcern(w=0))
          self.assertTrue(await new_coll.insert_one(doc))
          with self.assertRaises(OperationFailure):
              await coll.insert_one(doc)

          m = await self.async_rs_or_single_client(
              f"mongodb://{pair}/", replicaSet=async_client_context.replica_set_name
          )

          coll = m.pymongo_test.write_concern_test
          with self.assertRaises(OperationFailure):
              await coll.insert_one(doc)
          m = await self.async_rs_or_single_client(
              f"mongodb://{pair}/?w=0", replicaSet=async_client_context.replica_set_name
          )

          coll = m.pymongo_test.write_concern_test
          await coll.insert_one(doc)

          # Equality tests
          direct = await connected(await self.async_single_client(w=0))
          direct2 = await connected(
              await self.async_single_client(f"mongodb://{pair}/?w=0", **self.credentials)
          )
          self.assertEqual(direct, direct2)
          self.assertFalse(direct != direct2)
file /Users/shane/git/mongo-python-driver/test/asynchronous/conftest.py, line 25
  @pytest_asyncio.fixture(scope="package", autouse=True)
  async def test_setup_and_teardown():
      await async_setup()
      yield
      await async_teardown()
E       fixture 'test/asynchronous::<event_loop>' not found
>       available fixtures: _session_event_loop, _unittest_setUpClass_fixture_TestCommon, anyio_backend, anyio_backend_name, anyio_backend_options, cache, capfd, capfdbinary, caplog, capsys, capsysbinary, doctest_namespace, event_loop, event_loop_policy, monkeypatch, pytestconfig, record_property, record_testsuite_property, record_xml_attribute, recwarn, test/asynchronous/test_common.py::<event_loop>, test/asynchronous/test_common.py::TestCommon::<event_loop>, test_setup_and_teardown, tmp_path, tmp_path_factory, tmpdir, tmpdir_factory, unused_tcp_port, unused_tcp_port_factory, unused_udp_port, unused_udp_port_factory
>       use 'pytest --fixtures [testpath]' for help on them.

"session" seems to be the right thing for what we want there.

[NoahStapp]

I opened pytest-dev/pytest-asyncio#1052 about that exact error, it persists even if you explicitly mark a fixture as package.

With any pytest-asyncio scope, we'll still have two separate loops. That doesn't seem to be causing test failures, but it's something to be aware of for future debugging 😅

[ShaneHarvey]

Thanks I subscribed to that issue. However I did verify that the current code only ever uses 1 loop for the whole async test suite. Printing the loop that pytest-asyncio creates shows this: event_loop_fixture_id='_session_event_loop' which means the asyncio_default_fixture_loop_scope="session" in pyproject is behaving as expected.

[NoahStapp]

You mean that get_loop is picking up and using pytest's _session_event_loop? Or that that loop is separate from the loop the tests use that get_loop creates?

[ShaneHarvey]

The first one.

[ShaneHarvey]

Ready for another look.