[Python-Dev] Asynchronous context manager in a typical network server

[Szieberth Ádám]

Thanks for your reply Guido!

> - Instead of calling signal.signal() yourself, you should use
> loop.add_signal_handler(). It makes sure your signal handler doesn't run
> while another handler is already running.

I was opted to the signal module because `signal` documentation suggest that 
it alos supports Windows while asyncio documentation states that `loop.
add_signal_handler()` is UNIX only.

> - I'm unclear on why you want a wait_forever() instead of using
> loop.run_forever(). Can you clarify?

As I see `loop.run_forever()` is an issue from _outside_ while an `await 
wait_forever()` would be an _inside_ declaration making explicit what the task 
does (serving forever).

My OP suggest that it seemed to me quite helpful inside async context. 
However, I wanted to share my approach to get a confirmation that I am not on 
a totally wrong way with this.

> - In theory, instead of waiting for a Future that is cancelled by a
> handler, you should be able to use asyncio.sleep() with a very large number
> (e.g. a million seconds). 

I was thinking on this too but it seemed less explicit to me than awaiting a 
pure Future with a short comment. Moreover, even millions of seconds can pass.

> Your handler could then just call loop.stop().

For some reason I don't like bothering with the event loop from inside 
awaitables. It seems hacky to me since it breaks the hierarhy of who controlls 
who.

> However, I just tested this and it raises "RuntimeError: Event loop stopped
> before Future completed." so ignore this until we've fixed it. :-)

This is the exception I saw so many times by trying to close an asyncio 
program! I guess I am not the only one. This may be one of the most 
frustrating aspects of the library. Yet, it inspired me to figure out a plain 
pattern to avoid it, which may not the right one. However, I would like to 
signal that it would be nice to help developers with useful patterns and 
documentation to avoid RuntimeErrors and the frustration that goes with them.

Ádám
(http://szieberthadam.github.io/)

PS: I will replay to others as well, but first I had to play with my son. :)