Compose: Services cannot see each other. PG::ConnectionBad could not translate host name “pg” to address: No address associated with hostname

Created on 29 Apr 2018 · 8Comments · Source: docker/compose

Description of the issue

One service cannot see another in a composer file. While following this guide
https://docs.docker.com/compose/rails/
I get

C:\Users\Chloe\workspace\project\src>docker-compose run web rake db:create
Starting src_pg_1 ... done
could not translate host name "pg" to address: No address associated with hostname
Couldn't create database for {"adapter"=>"postgresql", "encoding"=>"unicode", "pool"=>5, "timeout"=>5000, "host"=>"pg", "username"=>"postgres", "password"=>nil, "database"=>"project"}
rake aborted!
PG::ConnectionBad: could not translate host name "pg" to address: No address associated with hostname

Context information (for bug reports)

docker-compose version 1.20.1, build 5d8c71b2

Docker version 18.03.0-ce, build 0520e24302

C:\Users\Chloe\workspace\fortuneempire\src>docker-compose config
services:
  cms:
    environment:
      JOOMLA_DB_HOST: mysql
      JOOMLA_DB_PASSWORD: example
    image: joomla
    links:
    - mysql:joomladb
    ports:
    - 8080:80/tcp
    restart: always
  mysql:
    environment:
      MYSQL_ROOT_PASSWORD: example
    image: mysql:5.6
    restart: always
  pg:
    image: postgres
    volumes:
    - /c/Users/Chloe/workspace/project/src/tmp/db:/var/lib/postgresql/data:rw
  web:
    build:
      context: C:\Users\Chloe\workspace\project\src
    command: bundle exec rails server -p 3000 -b '0.0.0.0'
    depends_on:
    - pg
    links:
    - pg
    ports:
    - 3000:3000/tcp
    volumes:
    - /c/Users/Chloe/workspace/project/src:/app:rw
version: '3.0'

Steps to reproduce the issue

Follow the guide here https://docs.docker.com/compose/rails/ except name db to pg.

Observed result

could not translate host name "pg" to address: No address associated with hostname

Expected result

Expected it to work without errors.

Stacktrace / full error message

Additional information

https://stackoverflow.com/questions/50090012/how-do-i-run-rails-in-docker-pgconnectionbad-could-not-translate-host-name-p

`docker-compose.yml`

version: '3'
services:
  pg:                                     ######### LOOK HERE!
    image: postgres
    volumes:
      - ./tmp/db:/var/lib/postgresql/data
  web:
    build: .
    command: bundle exec rails server -p 3000 -b '0.0.0.0'
    volumes:
      - .:/app
    ports:
      - "3000:3000"
    depends_on:
      - pg
    links:
      - pg                                     ######### LOOK HERE!
  cms:
    image: joomla
    restart: always
    links:
      - mysql:joomladb
    ports:
      - 8080:80
    environment:
      JOOMLA_DB_HOST: mysql
      JOOMLA_DB_PASSWORD: example
  mysql:
    image: mysql:5.6
    restart: always
    environment:
      MYSQL_ROOT_PASSWORD: example

`config/database.yml`

# SQLite version 3.x
#   gem install sqlite3
#
#   Ensure the SQLite 3 gem is defined in your Gemfile
#   gem 'sqlite3'
#
default: &default
  adapter: postgresql
  encoding: unicode
  pool: 5
  timeout: 5000
  host: pg                                     ######### LOOK HERE!
  username: postgres
  password:

development:
  <<: *default
  database: project

# Warning: The database defined as "test" will be erased and
# re-generated from your development database when you run "rake".
# Do not set this db to the same as development or production.
test:
  <<: *default
  database: project_test

production:
  <<: *default
  database: project

Windows 8.1.
docker-compose install method via chocolatey install docker-toolbox.

Source