feat: add a new tutor dev attach command to attach running containers for debugging

[Danyal-Faheem]

Edx-platform developers regularly utilize debuggers inside their codebase and the tutor dev start command does not allow attaching to containers on certain OSes such as MacOS. This command will allow users to attach a single running container using the docker compose attach command.

Caveats:

• Can only attach one service in one running terminal

[kdmccormick]

Thanks for the PR Danyal! This is a problem I have noticed on Ubuntu as well. I'm able to attach to an individual container's stdout by doing, for example, tutor dev start cms, which is what the docs recommend. But I'm not able to run any debugger commands, so it seems that stdin is detached.

I'm not super keen to add a new command, but breakpoint debugging is definitely something we all need. I'll test this out and leave a review soon.

[regisb]

I was hoping I was the only one who observed that issue... The problem is that, in my case, docker compose attach does not work either. I need to run docker attach <containerID>. Is it the case for you as well?

EDIT: actually, tutor dev dc attach lms does allow me to stop at breakpoints. But when I attempt to attach to a running container with tutor dev start lms, adding a breakpoint yields the following error:

WARNING: your terminal doesn't support cursor position requests (CPR).

[Danyal-Faheem]

@regisb, I get the same error as you do which prompted me to make this PR.

I also initially thought that docker compose attach <container> wouldn't work and I would need to do docker attach <container> instead, but to my surprise, it works perfectly.

[kdmccormick]

This is working great for me. Can you update those dev docs that I linked in my comment above?

EDIT: In the dev docs, please also mention that the way to detach from the container without shutting it down is to send Ctrl-p Ctrl-q.

[Danyal-Faheem]

Hey @kdmccormick, I've updated the docs as well. Can you take another look and let me know what you think?

[regisb]

Based on my experience, it seems that docker compose up no longer attaches stdin to the specified containers. I'm wondering what the right fix should be. Is it to add a new command? Or should we automatically run docker compose attach when we run tutor dev start <a single container>?

[kdmccormick]

@regisb , I really like that idea, especially since I cannot imagine any situation where I run tutor dev start lms without wanting stdin to be attached.

There is only one minor problem:

• To escape from docker compose up without stopping containers, the sequence is Ctrl-z
• To escape from docker compose attach without stopping containers, the sequence is Ctrl-p Ctrl-q

If we went with your proposal, that would mean that tutor ... start would have different escape sequences depending on whether you provided zero/multiple argument versus 1 argument. Perhaps we could mitigate the confusion with good docs and by printing a helpful message, like: ℹ️ To detach without stopping the platform, type: .....

What do you think @regisb , go forward with modifying tutor ... start, or stick with tutor dev attach?

[regisb]

Perhaps we could mitigate the confusion with good docs and by printing a helpful message, like: ℹ️ To detach without stopping the platform, type: .....

Yes, I think we should do that. I honestly didn't know about escape commands, as I just ctrl+c all the time. In the process I just discovered that we also need to ctrl+p+q on tutor dev run.

So my vote goes to changing the "start" command. Especially since it's so easy to run tutor dev dc attach, I don't really see a point of adding another command.