Controller.start uses threading

[samuelcolvin]

aiosmtpd/aiosmtpd/controller.py

Line 54 in 3ced778

self._thread = threading.Thread(target=self._run, args=(ready_event,))

It seems to be that Controller.start using Threading is not required and will lead to problems.

Like the asyncio http server starting an SMTP server should not involve threading, but just loop.run_forever().

[waynew]

@samuelcolvin thanks for the report! Do you have some docs or examples that we could reference?

[samuelcolvin]

Take a look at aiohttp's run_app or its documentation on Runnings Applications.

[pepoluan]

@samuelcolvin so if I don't misunderstood, you want to split out the thread-starting ability from Controller?

Because currently all those code in Controller enables the event loop to run without blocking the main thread. If we take out the thread-creation part, then invoking run_forever() will block.

And this will be a major, very impactful breaking behavioral change for existing users.

EDIT: Rather than changing the existing Controller class, we can create a new class -- we can call it UnthreadedController or somesuch -- where the threading circuitry is taken out. So if user really wants to handle their own multithreading/multiprocessing management, they can use that class instead. Users already using existing Controller class don't have to do anything on their end.

[nhoad]

Why is the default behavior to run in a thread?

Mirroring Samuel's request, having the ability to run it in the foreground without any threading would be useful.

[pepoluan]

@nhoad One thing to realize is that Controller is just a "convenience class" to instantiate the SMTP server.

The code for Controller is very well designed; if you need a non-threading, in-the-foreground solution, you can simply take the code within the Controller._run() method (that is, select the text, copy them, and paste in your code) and run it.

All the intelligence of the SMTP server happens in the aiosmtpd.smtp.SMTP class; it's self-contained.

[pepoluan]

I have a branch on my laptop, currently waiting for #247 to be merged first because it's based on that.

[pepoluan]

Boy oh boy... apparently implementing unthreaded controllers is much more complex than I thought.

Testing them properly is a whole 'nother level.

[pepoluan]

If anyone wants to take a peek and/or kick the tires, be my guest: https://github.com/pepoluan/aiosmtpd/tree/unthreaded-controller

[pepoluan]

The branch is about 99% complete, documentation also updated. Passes all tests on Windows and WSL (no time to test it on FreeBSD and OpenSUSE yet)

Feel free to check it out @samuelcolvin @nhoad