Use the command keyword in docker-compose

Question

Im trying to figure out how to properly use the command key word in a docker-compose.yml

Im trying to execute the following commands:

cd ./wait-for-it
wait-for-it.sh postgres:5432
cd
cd ./api
yarn start

I can structure it like this

command: ["./wait-for-it/wait-for-it.sh", "postgres:5432", "--", "yarn", "start"]

However I don't know how to cd into api before doing yarn

Any thoughts on how to structure the command properly?

nop that brings me back to the home directory modifying to make clearer — lucas rodriguez, Apr 25 '20 at 15:43
Ah interesting, TIL. Do you know which *part* of that command fails then? What container is it running in? You could also try the `--cwd` flag to Yarn. — jonrsharpe, Apr 25 '20 at 15:45
Further edit, Its no currently failing im just missing a part of the command, executing the `yarn` from `./api` instead of the woking directory — lucas rodriguez, Apr 25 '20 at 15:49
Does this answer your question? [Run yarn in a different path](https://stackoverflow.com/questions/46891622/run-yarn-in-a-different-path) — jonrsharpe, Apr 25 '20 at 15:51
This doesnt seem to work unfotunately, I get an error saying the directory doesn't exist but running: `command: ["./wait-for-it/wait-for-it.sh", "postgres:5432", "--", "./api","yarn", "start"]` returns `./api is a directory` — lucas rodriguez, Apr 25 '20 at 15:59

score 1 · Accepted Answer · answered Apr 25 '20 at 17:48

The absolute best way to manage complex startup commands like this is to (a) write them as shell scripts and (b) bake them into your Docker image.

For instance, I can reinterpret the startup procedure that you wrote as pseudocode like:

1. cd into the wait-for-it directory and run the wait-for-it script
2. Do the thing the container was originally going to do

I can translate that into a shell script:

#!/bin/sh
(cd /app/wait-for-it && ./wait-for-it.sh "$DB_HOST_PORT")
exec "$@"

Then I can use that script as an ENTRYPOINT in my image. It runs the cd command in a subshell so it returns back to the original directory on the next line; the exec "$@" line runs what was passed as a command. The end of your Dockerfile would look like:

COPY entrypoint.sh /app
RUN chmod +x entrypoint.sh

WORKDIR /app/api
ENTRYPOINT ["/app/entrypoint.sh"]
CMD ["yarn", "start"]

Then I don't need to manually override these settings in the docker-compose.yml at all; the only thing I need to do is to provide the database location as an environment variable.

version: '3'
services:
  myapp:
    build: .
    environment:
      - DB_HOST_PORT=postgres:5432
    ports:
      - '3000:3000'
  postgres:
    image: postgres:12

If I wanted to run some other command:

docker-compose run myapp yarn migrate

It would still wait for the database to be available, but then run the alternate command.

Use the command keyword in docker-compose

1 Answers1