Error starting sidekiq in Docker: "Please point sidekiq to a Rails 4/5 application"

Question

Rails 5.2, Docker Compose, Sidekiq, Redis.

This is the docker-compose file:

version: '3.6'

services:
  redis:
    image: 'redis:4.0-alpine'
    command: redis-server
    ports:
      - '6379:6379'
    volumes:
      - 'redis:/data'

  sidekiq:
    depends_on:
      - 'redis'
    build: .
    command: bundle exec sidekiq -C config/sidekiq.yml
    volumes:
      - './:/app'
    env_file:
      - '.env'

  api:
    build: .
    volumes:
      - './:/app'
    working_dir: /app
    command: puma
    ports:
      - 3000:3000
    depends_on:
      - db
      - redis
    environment:
      DATABASE_URL: postgres://postgres@db
  db:
    image: postgres:10.3-alpine

volumes:
  redis:
  postgres:

It seems sidekiq cannot find my Rails app.

If I change sidekiq to start like this:

    command: bundle exec sidekiq -C config/sidekiq.yml -r /app

then I get this error:

Spring was unable to find your config/application.rb file. Your project root was detected at /api, so spring looked for /api/config/application.rb but it doesn't exist. You can configure the root of your application by setting Spring.application_root in config/spring.rb.

If I instead add the working_dir setting to sidekiq:

sidekiq:
    depends_on:
      - 'redis'
    build: .
    command: bundle exec sidekiq -C config/sidekiq.yml
    volumes:
      - './:/app'
    env_file:
      - '.env'
    working_dir: 
      - '/app'

then I get this error:

2019-05-27T20:27:59.770Z 1 TID-gr1e0d7n5 INFO: Booting Sidekiq 5.1.1 with redis options {:url=>"redis://redis:6379/0", :id=>"Sidekiq-server-PID-1"}
sidekiq_1  | could not connect to server: No such file or directory
sidekiq_1  |    Is the server running locally and accepting
sidekiq_1  |    connections on Unix domain socket "/tmp/.s.PGSQL.5432"?

So how do I make sidekiq start correctly in its container?

I have seen these answers, which are similar but not this particular error:

Question 1

Question 2

Question 3

Question 4

Answer 1

It seems sidekiq could not find the Rails app, which is fixed by adding the 'working-dir' setting, and then it could not find postgres, so I had to add the environment setting to point to postgres.

The final compose file is:

version: '3.6'

services:
  db:
    image: postgres:10.3-alpine
    ports:
      - '5432:5432'

  redis:
    image: 'redis:4.0-alpine'
    command: redis-server
    ports:
      - '6379:6379'
    volumes:
      - 'redis:/data'

  sidekiq:
    depends_on:
      - 'db'
      - 'redis'
    build: .
    command: bundle exec sidekiq -C config/sidekiq.yml
    volumes:
      - './:/app'
    env_file:
      - '.env'
    working_dir: /app
    environment:
      DATABASE_URL: postgres://postgres@db

  api:
    build: .
    volumes:
      - './:/app'
    working_dir: /app
    command: puma
    ports:
      - 3000:3000
    depends_on:
      - db
      - redis
    environment:
      DATABASE_URL: postgres://postgres@db

volumes:
  redis:
  postgres: