Question 82465 in Docker Question posted in
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Docker conditionally exposing port for debugger

I would like to conditionally open a debug port on one of the services in our docker-compose.yml file when we want to run the debugger.

services:
  service-one:
    ports:
      - "3000:3000"
      - "1234:1234" # debugger port - conditionally allow based on env var or cmd line

  service- two:
    ...
  service-three:
    ...

We are running all of these services but for service-one we want to conditionally open 1234 if it’s debug mode.

Can that be done by passing a command line in docker-compose up ?
docker-compose up --env-file .env.debug

Or can we do it some other way like using build stages in our Dockerfile and somehow targeting debugging vs non-debugging ?

Tags:

2

Answers


  1. 0

    You could achieve it using docker-compose profiles. Here’s an excerpt from compose documentation

    version: "3.9"
services:
  frontend:
    image: frontend
    profiles: ["frontend"]

  phpmyadmin:
    image: phpmyadmin
    depends_on:
      - db
    profiles:
      - debug

  backend:
    image: backend

  db:
    image: mysql

    Here the services frontend and phpmyadmin are assigned to the profiles frontend and debug respectively and as such are only started when their respective profiles are enabled.

    Services without a profiles attribute will always be enabled, i.e. in this case running docker-compose up would only start backend and db.

    Valid profile names follow the regex format of [a-zA-Z0-9][a-zA-Z0-9_.-]+.

    Note

    The core services of your application should not be assigned profiles so they will always be enabled and automatically started.

    Enabling profiles
    To enable a profile supply the –profile command-line option or use the COMPOSE_PROFILES environment variable:

    $ docker-compose –profile debug up
    $ COMPOSE_PROFILES=debug docker-compose up
    The above command would both start your application with the debug profile enabled. Using the docker-compose.yml file above, this would start the services backend, db and phpmyadmin.

    So essentially have 2 containers for the same service with desired number of ports and start docker-compose using appropriate profiles

    Reference: https://docs.docker.com/compose/profiles/

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  2. 0

    You could probably do this with multiple Compose files. You can have a normal docker-compose.yml that sets up the service as you’d normally run it:

    version: '3.8'
services:
  service-one:
    image: registry.example.com/service/one:${SERVICE_ONE_TAG:latest}
    ports:
      - '3000:3000'
    environment:
      - SERVICE_TWO_URL=http://service-two:3000/
  service-two: { ... }

    And then a second docker-compose.debug.yml that has only the settings specific to the debugger setup.

    version: '3.8'
services:
  service-one:
    ports:
      - '1234:1234'
    environment:
      - DEBUG_PORT=1234

    Now if you run

    docker-compose -f docker-compose.yml -f docker-compose.debug.yml up

    (and you need both -f options, with every docker-compose command, while you’re using this setup) then it will take the image: from the first file, and combine the ports: and environment: from both files. When you don’t need the debugger, remove the -f docker-compose.debug.yml option and it will only use the settings from the base file.

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