Cannot attach docker container with `debugger` while `pry.binding` can

[eggplants]

Your environment

• ruby -v: ruby 3.0.6p216 (2023-03-30 revision 23a532679b) [x86_64-darwin22]
• rdbg -v: rdbg 1.8.0 {:mode=>:start, :no_color=>nil}

Describe the bug

I tried to set breakpoint within Rails constroller:

class FooController < ApplicationController
  def create
    ...
    debugger
  end
end

And then I ran docker compose up and sent request to the method with curl. After launching debugger, I couldn't attach to the container process running rails service by docker attach bar-web-1.

Interestingly, I then installed pry-byebug and replaced debugger with pry.binding and was able to attach without problems.

No one else seemed to have this problem　on the web, so I could be doing something wrong.

To Reproduce TBD

Expected behavior User must be able to attach with docker attach even if degug gem's debugger is launched.

Additional context TBD

[ko1]

I have no idea about it. Have you verified that debugger method is invoked?

[eggplants]

Yes. The debug gem's debugger has shown in docker console when runtime ruby has reached the debugger line.

[ko1]

Let me clear the repro process.

• 1. (D(ocker)) docker run with detached mode
• 2. (D) Rails server starts
• 3. (C(lient)) curl
• 4. (D) debugger method is invoked
• 5. (C) docker attach

Questions:

• please correct me if the process is wrong.
• and what happens after (5)?
• How to invoke rails server in docker container?
• Could you repro with simple ruby program instead of Rails program?

Thanks, Koichi

[eggplants]

Thank you. I'll create MRE code soon.