Multiple tasks running along Microdot

[mdughera]

Not sure if this is the right place to ask: apologies in advance if you have to move it somewhere else.

In Microdot v1 the code below works:

loop = asyncio.get_event_loop()
loop.create_task(watchdog()) 
loop.create_task(ap()) 
loop.create_task(ws.start_server(port=80, debug=True))
loop.run_forever()

but it does not work in v2.
The provided examples suggest using a different approach:

async def main():
server = asyncio.create_task(app.start_server())
# ... do other asynchronous work here ...
# cleanup before ending the application
await server

asyncio.run(main())

the result I want to obtain is that even though a task stops working the remaining keep on running unaffected.
If the v1 solution no longer works, what is the suggested way to obtain the same result in v2?

[miguelgrinberg]

Can you explain what is the issue when you use the first code example in Microdot v2?

[miguelgrinberg]

Update: I'm not finding any issues running the server with your code, so my guess is that there is something in your own application that is causing the server to block.

[mdughera]

I tried also on my side and I see that reproducing the issue is not straightforward.
The only thing that is sure is that the same code running on Microdot v1 since more than an year does not run on Microdot v2.
I made it work with v2 by emptying some classes that are imported in my project but it seems it is not a matter of code that breaks it rather than the "quantity" of the code that I removed.
I'll do some further investigation and let you know if I find something interesting.

[mdughera]

Hi Miguel,

I tried to isolate the problem in my code and I discovered what follows.

Only importing microdot v2, even without creating an instance or routes, causes problems to the other tasks that use BLE or WIFI in tasks.

If I remove from the beginning of the microdot code the following:

try:
    from inspect import iscoroutinefunction, iscoroutine
    from functools import partial

    async def invoke_handler(handler, *args, **kwargs):
        """Invoke a handler and return the result.

        This method runs sync handlers in a thread pool executor.
        """
        if iscoroutinefunction(handler):
            ret = await handler(*args, **kwargs)
        else:
            ret = await asyncio.get_running_loop().run_in_executor(
                None, partial(handler, *args, **kwargs))
        return ret
except ImportError:  # pragma: no cover
    def iscoroutine(coro):
        return hasattr(coro, 'send') and hasattr(coro, 'throw')

    async def invoke_handler(handler, *args, **kwargs):
        """Invoke a handler and return the result.

        This method runs sync handlers in the asyncio thread, which can
        potentially cause blocking and performance issues.
        """
        ret = handler(*args, **kwargs)
        if iscoroutine(ret):
            ret = await ret
        return ret

the import does not cause problems but obviously the webserver cannot be started.
Please note also that in my environment both inspect and functools do not exist.

Does this ring a bell for you?

Marco

[miguelgrinberg]

You need to create an example that reproduces the problem so that I can debug it here. I don't understand what you mean by "causes problems to the other tasks". Some code from the top of the microdot.py should not have an effect on unrelated tasks that do not use microdot, right? I need to have a better understanding of what you are seeing to be able to comment on this.

[mdughera]

I finally solved the problem in my setup, even though I have not completely understood the cause.
I tried but not succeded to create a barebones example that I could share.
I solved the problem by changing the import order of the various libraries, moving microdot at the very beginning.
The conflicting libraries contain only definitions of static classes that get executed in the main loop.
Even without any scheduled tasks, importing libraries in the wrong order causes the wifi stack to stop working.

I propose then to consider this discussion closed and possibly reopen another if needed.

thanks for your support,

Marco