bug#66669: 30.0.50; [EGLOT] Emacs freezes when server sends a ton of progress notifications

[João Távora]

On Sat, Oct 21, 2023 at 8:11 PM Yuan Fu <casouri@gmail.com> wrote:
>
> X-Debbugs-CC: joaotavora@gmail.com
>
> I use rust’s language server (rust-analyzer) with eglot. And
> whenever I turn eglot on for a project, Emacs freezes for a good
> 30 seconds, busy updating the eglot progress indicator, before I
> can do anything. I think the reason is that the rust language server
> sends a ton of progress notifications, which completely blocks Emacs
> before it’s done.

hi Yuan,

Two things:

* Would be nice to have a reproduction recipe.  I have rust-analyzer but
  one project where I try it regularly, the "bevy" graphics engine [1]
  Seems to work OK there.  You say "a project", but for bevy
  it starts up fast (maybe not even half a second) and works quite well.

  No Emacs freeze at all.  Tried removing the cache with git clean -fdx and
  I get all the notifications cleanly with no slowdown.

  So please include Emacs versions (master preferred, should be trivial
  for you), Eglot version, rust-analyzer version and preferably an Emacs
  -Q invocation with the simplest Rust project you can share that
  exhibits this behaviour.

* Have you profiled?  Have you tried setting eglot-events-buffer-size
  to 0 (and restart Eglot) as suggested in the Eglot manual?  Many
  performance problems are due to JSON objects being pretty printed in
  the Eglot events buffer (BTW some users ask me to  turn it to 0 by
  default, but the pros don't outweigh the cons, which in this case is
  we would lose a valuable tool for newbie users with exotic servers to
  send me their debug data easily)

João

[1] https://github.com/bevyengine/bevy