Docker: Docker-compose ruby + postgres - PG::ConnectionBadcould not connect to server

Question

I created Dockerfile to ruby from official docker-compose website. I used docker compose to integrate this with Postgres. When docker-compose up, then PostgreSQL starts but I cannot connect to this. The main problem is in ruby database config because I can't change to listen to another host and set the default user. I don't know how to connect these two containers without changing the ruby database config.

Dockerfile

FROM ruby:2.3.4
RUN apt-get update -qq && apt-get install -y build-essential libpq-dev nodejs
RUN mkdir /myapp
WORKDIR /myapp
ADD Gemfile /myapp/Gemfile
ADD Gemfile.lock /myapp/Gemfile.lock
RUN bundle install
ADD . /myapp

Docker-compose

version: '3'
services:
  db:
    image: postgres:9.6
    ports:
      - "5432:5432"
  web:
    build: .
    ports:
      - "4000:4000"
    depends_on:
      - db

Ruby database.yml

default: &default
  adapter: postgresql
  encoding: unicode
  pool: 5

development:
  <<: *default
  database: project_development

If i run inside web conatiner "bundle exec rake db:create I get error:

psql: could not connect to server: No such file or directory
Is the server running locally and accepting
connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?

I don't know what env set that will connect together.

Bartosz Bonisławski · Accepted Answer · 2017-07-04 09:45:44Z

3

You didn't specify database host in your database.yml. Set it to db or just try this database.yml

development: &default
  adapter: postgresql
  encoding: unicode
  database: project_development
  pool: 5
  username: postgres
  password:
  host: db

test:
  <<: *default
  database: project_test

answered Jul 4, 2017 at 9:45

Bartosz Bonisławski

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2 Comments

Michał Niedziela Over a year ago

I used similar database.yml and everything work, but I can't change database.yml. So this solution doesn't solve problem. I don't know what I must add to docker config, that will be help to connect.

Promise Preston Over a year ago

Thank you so much for this. It saved me a lot of stress. My host is database but I didn't have a host defined in my database.yml file. After defining it , everything worked fine.

nattfodd · Accepted Answer · 2017-07-04 09:43:47Z

1

You should update your database.yml with the following:

  database: ENV['DB_NAME']
  username: ENV['DB_USERNAME']
  password: ENV['DB_PASSWORD']

There's no such thing as "default PG user", so you have to create your own user with a proper permissions.

So, once you have a PG user created inside of container, you can update your docker-compose.yml file with a proper DB settings:

web:
  environment:
    - DB_NAME=rails_development
    - DB_USERNAME=rails_user
    - DB_PASSWORD=rails_password

Also, you probably want to mount local storage of postgres in your docker-compose.yml to keep data when container restarts:

volumes:
  - /var/lib/postgresql/data

answered Jul 4, 2017 at 9:43

nattfodd

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1 Comment

Bartosz Bonisławski Over a year ago

There is default user named postgres with empty password in docker images of postgres, so you don't have to create it. Your solution doesn't solve problem mentioned by author of question

Promise Preston · Accepted Answer · 2020-11-01 06:09:08Z

Just to add to Bartosz Bonisławski's answer.

I encountered this issue when building a Rails application on Ubuntu 18.04.

My Dockerfile for my development environment which was located in docker/development/Dockerfile directory of my project was defined like this:

version: '3'

services:
  app:
    build:
      context: .
      dockerfile: ./docker/${RAILS_ENV}/Dockerfile
    depends_on:
      - database
      - redis
    ports:
      - "3000:3000"
    restart: always
    volumes:
      - .:/app
      - gem-cache:/usr/local/bundle/gems
      - node-modules:/app/node_modules
    env_file:
      - .env
    environment:
      RAILS_ENV: ${RAILS_ENV}
      RACK_ENV: ${RACK_ENV}

  database:
    image: postgres:12.1
    expose:
      - "5432"
    restart: always
    env_file:
      - .env
    environment:
      POSTGRES_USER: ${DATABASE_USER}
      POSTGRES_PASSWORD: ${DATABASE_PASSWORD}
      POSTGRES_DB: ${DATABASE_NAME}
      POSTGRES_HOST_AUTH_METHOD: ${DATABASE_HOST}

    volumes:
      - postgres-data:/var/lib/postgresql/data
volumes:
  gem-cache:
    driver: local
  node-modules:
    driver: local
  postgres-data:
    driver: local

While my .env file was defined as this:

DATABASE_USER=myapp_user
DATABASE_PASSWORD=myapp_password
DATABASE_NAME=myapp_development
DATABASE_HOST=database
DATABASE_PORT=5432

RAILS_ENV=development
RACK_ENV=development

The issue I had was that I did not add host config to my database.yml file of my project. So I was encountering the error:

psql: could not connect to server: No such file or directory Is the server running locally and accepting connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?

Here's how I solved:

I simply added it like this and it worked perfectly fine:

default: &default
  adapter: postgresql
  encoding: unicode
  # For details on connection pooling, see Rails configuration guide
  # https://guides.rubyonrails.org/configuring.html#database-pooling
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>

development:
  <<: *default
  database: <%= ENV['DATABASE_NAME'] %>
  username: <%= ENV['DATABASE_USER'] %>
  password: <%= ENV['DATABASE_PASSWORD'] %>
  host: <%= ENV['DATABASE_HOST'] %>
  port: <%= ENV['DATABASE_PORT'] %>

That's all.

I hope this helps

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