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Rails on Docker: ActiveRecord::ConnectionNotEstablished: could not translate host name to address: Try again

June 13, 2022

I’m trying to dockerize my Ruby on Rails API, the output of the command "docker-compose ps" is this:

Since the containers are up, I tried to migrate my database use this command "docker-compose exec app bundle exec rails db:setup db:migrate", the output I got is this:

About my config file, this is my Dockerfile:

FROM ruby:2.7.0-alpine

ENV BUNDLER_VERSION=2.1.2

RUN apk add --update --no-cache \
      binutils-gold \
      build-base \
      curl \
      file \
      g++ \
      gcc \
      git \
      less \
      libstdc++ \
      libffi-dev \
      libc-dev \
      linux-headers \
      libxml2-dev \
      libxslt-dev \
      libgcrypt-dev \
      make \
      netcat-openbsd \
      nodejs \
      openssl \
      pkgconfig \
      postgresql-dev \
      python \
      tzdata \
      yarn

RUN gem install bundler -v 2.1.2

WORKDIR /app

COPY Gemfile Gemfile.lock ./

RUN bundle config build.nokogiri --use-system-libraries

RUN bundle check || bundle install

#COPY package.json yarn.lock ./

RUN yarn install --check-files

COPY . ./

ENTRYPOINT ["./entrypoints/docker-entrypoint.sh"]

And this is my docker-compose.yml:

version: '3.4'

services:
  app:
    build:
      context: .
      dockerfile: Dockerfile
    depends_on:
      - database
    ports:
      - "3000:3000"
    volumes:
      - .:/app
      - gem_cache:/usr/local/bundle/gems
      - node_modules:/app/node_modules
    env_file: .env
    environment:
      RAILS_ENV: production
    networks:
      - letsorder

  database:
    image: postgres:13.7
    env_file:
      - ./.env
    volumes:
      - db_data:/var/lib/postgresql/data
      - ./init.sql:/docker-entrypoint-initdb.d/init.sql
    networks:
      - letsorder


volumes:
  gem_cache:
  db_data:
  node_modules:

networks:
  letsorder:
    driver: bridge

So, I searched this issue, most of them lead to set-up a network adapter in my docker-compose.yml, I did it but I got the same error.

I would like to request your suggestions and comments how to debug and fix this issue; thanks a lot.

>Solution :

It looks like in your database.yml file you have something like

host: rorletsorderdatabase

But in your docker-compose.yml file you have

  database:
    foo

A possible fix is changing the host inside your database.yml file

  host: database

Another option is changing the service name inside your docker-compose.yml file

  rorletsorderdatabase:
    image: postgres:13.7
      env_file:
        - ./.env
      volumes:
        - db_data:/var/lib/postgresql/data
        - ./init.sql:/docker-entrypoint-initdb.d/init.sql
      networks:
        - letsorder

Also in any of the cases, you need to expose the pg port 5432 in the service definition inside docker-compose.yml