Unit test `on_window_close` for window aggregation

[thomas-chauvet]

Checklist

• [ x] I have included information about relevant versions

I am using faust in the latest version 0.8.11.

• [ ] I have verified that the issue persists when using the master branch of Faust.

Steps to reproduce

Based on the windowed aggregation example provided I am trying to unit test the function window_processor.

When I send event based on doc I am not able to see when window_processor is triggered.

Expected behavior

I expect to be able to check that window has been triggered.

Actual behavior

I can see that tumbling_table.table.last_closed_window is 0.0. I guess the window is never close.

Versions

• Python version: 3.9
• Faust version: 0.8.11
• Operating system: MacOS

Update: I've pushed a small repo with an example here.

[wbarnha]

Thanks for providing an example with a unit test included, this will make it much easier to troubleshoot. Looking through our current unit tests, there don't seem to be any tests that verify cases such as tumbling_table.table.last_closed_window != 0. I'll look into changing that and hopefully providing a fix for you.

[wbarnha]

I ran the example of windowed_aggregation.py and changed the configuration similar to what you have, except an extra print statement:

@app.agent(source)
async def print_windowed_events(stream):
    async for event in stream:
        value_list = tumbling_table['events'].value()
        value_list.append(event)
        tumbling_table['events'] = value_list
        print("last closed table:", tumbling_table.table.last_closed_window)

I saw the last_closed_window value update just fine after 5 seconds (as provided in your configuration), so I'm not sure if your test has issues.

[thomas-chauvet]

Yes, it works well in the "normal" case.

The case where I cannot see the correct last_closed_window and it stays at 0 is when we run in test_context in unit test.

It also blocks the test for function on_window_close.

[wbarnha]

See https://github.com/faust-streaming/faust/pull/391 for an internal test of last_closed_window. I'll need to think more about what's going on in your repo.