Pluggable event loop task scheduler

[trustin]

Netty currently only provides a priority queue based task scheduler. We could add a small abstraction layer between EventExecutor and a task scheduler implementation so that a user can choose his or her favorite scheduler algorithm, most notably, hashed wheel timer, which is more scalable.

(Inspired by an e-mail question by Mac Atre.)

[azhsmesos]

Do you have any proposal? I want to know how to realize it

[normanmaurer]

there is no proposal

[trustin]

Basic idea is to allow a user choose between priority queue and hashed wheel timer for scheduled tasks. The latter would be desirable for very busy event loop with lots of timeout-like tasks. That being said, it doesn't really need to be an abstraction layer although that'd be nice to have.

[injae-kim]

1. Basic idea is to allow a user choose between priority queue and hashed wheel timer for scheduled tasks
2. it doesn't really need to be an abstraction layer although that'd be nice to have.

Can I handle this issue? I'll make PR based on above proposal~! 🙇

[He-Pin]

@injae-kim Cool, I will review it:) I need this too.

[injae-kim]

#13552

Cause this is my first PR on netty, I made simple DRAFT PR to check my direction is correct! PTAL 🙇