How to debug a rails app in docker with pry?

ruby-on-rails docker pry
fey picture fey · Feb 4, 2016 · Viewed 19.8k times · Source

I have a rails app running in a docker container in development environment.

When I try to debug it with placing binding.pry somewhere in the code and attaching to the container I can see the pry prompt in the output but it doesn't pause on it and I can't interact with it like it was without docker container.

So how do I debug a containerized app?

Answer

Gabe Kopley picture Gabe Kopley · May 17, 2016

If you're using docker-compose, you can add these flags to docker-compose.yml:

app:
  tty: true
  stdin_open: true

And then attach to your process with docker attach project_app_1. pry-rails works here now. Ensure less is installed on your container for the optimal pry experience.

cf. https://github.com/docker/compose/issues/423#issuecomment-141995398

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