Docker: Is the server running on host "localhost" (::1) and accepting TCP/IP connections on port 5432?

Question

I am getting issues while setup and run the docker instance on my local system with Ruby on Rail. Please see my docker configuration files:-

Dockerfile

FROM ruby:2.3.1

RUN useradd -ms /bin/bash web
RUN apt-get update -qq && apt-get install -y build-essential
RUN apt-get -y install nginx
RUN apt-get -y install sudo
# for postgres
RUN apt-get install -y libpq-dev

# for nokogiri
RUN apt-get install -y libxml2-dev libxslt1-dev

# for a JS runtime
RUN apt-get install -y nodejs
RUN apt-get update

# For docker cache
WORKDIR /tmp 
ADD ./Gemfile Gemfile
ADD ./Gemfile.lock Gemfile.lock
ENV BUNDLE_PATH /bundle
RUN gem install bundler --no-rdoc --no-ri
RUN bundle install
# END
ENV APP_HOME /home/web/cluetap_app
RUN mkdir -p $APP_HOME
WORKDIR $APP_HOME
ADD . $APP_HOME
RUN chown -R web:web $APP_HOME
ADD ./nginx/nginx.conf /etc/nginx/
RUN unlink /etc/nginx/sites-enabled/default
ADD ./nginx/cluetap_nginx.conf /etc/nginx/sites-available/
RUN ln -s /etc/nginx/sites-available/cluetap_nginx.conf /etc/nginx/sites-enabled/cluetap_nginx.conf
RUN usermod -a -G sudo web

docker-compose.yml

version: '2'
services:
  postgres:
    image: 'postgres:9.6'
    environment:
      - PGDATA=/var/lib/postgresql/data/pgdata
      - POSTGRES_PASSWORD=
      - POSTGRES_USER=postgres
      - POSTGRES_HOST=cluetapapi_postgres_1
    networks:
      - default
      - service-proxy
    ports:
      - '5432:5432'
    volumes:
      - 'postgres:/var/lib/postgresql/data'
    labels:
      description: "Postgresql Database"
      service: "postgresql"
  web:
    container_name: cluetap_api
    build: .
    command: bash -c "thin start -C config/thin/development.yml && nginx -g 'daemon off;'"
    volumes:
      - .:/home/web/cluetap_app
    ports:
      - "80:80"
    depends_on:
      - 'postgres'
networks:
  service-proxy:
volumes:
  postgres:

When I have run docker-compose build and docker-compose up -d these two commands it run succesfully but when I have hit from the url the it thorught internal server error and the error is

Unexpected error while processing request: could not connect to server: Connection refused
    Is the server running on host "localhost" (127.0.0.1) and accepting
    TCP/IP connections on port 5432?
could not connect to server: Cannot assign requested address
    Is the server running on host "localhost" (::1) and accepting
    TCP/IP connections on port 5432?

I have applied some solution but it did not work for me, please guide me I am new to docker and AWS.

Answer 1

The issue is that you are trying to connect to localhost inside the container for DB. The port mapping that you do 5432:5432 for postgres map 5432 to localhost of your host machine.

Now your web container code is running inside the container. And there is nothing on its localhost:5432.

So you need to change your connection details in the config to connect to postgres:5432 and this is because you named the postgres DB service as postgres

Change that and it should work.

Answer 2

By default the postgres image is already exposing to 5432 so you can just remove that part in your yml.

Then if you would like to check if web service can connect to your postgres service you can run this docker-compose exec web curl postgres:5432 then it should return:

curl: (52) Empty reply from server

If it cannot connect it will return:

curl: (6) Could not resolve host: postgres or curl: (7) Failed to connect to postgres port 5432: Connection refused

UPDATE:

I know the problem now. It's because you are trying to connect on the localhost you should connect to the postgres service.

Answer 3

I had this same issue when working on a Rails 6 application in Ubuntu 20.04 using Docker and Traefik.

In my case I was trying to connect the Ruby on Rails application running in a docker container to the PostgreSQL database running on the host.

So each time I try to connect to the database I get the error:

Unexpected error while processing request: could not connect to server: Connection refused
    Is the server running on host "localhost" (127.0.0.1) and accepting
    TCP/IP connections on port 5432?
could not connect to server: Cannot assign requested address
    Is the server running on host "localhost" (::1) and accepting
    TCP/IP connections on port 5432?

Here's how I fixed it:

So first the applications running in the container are exposed to the host via Traefik which maps to the host on port 80.

Firstly, I had to modify my PostgreSQL database configuration file to accept remote connections from other IP addresses. This Stack Overflow answer can help with that - PostgreSQL: FATAL - Peer authentication failed for user (PG::ConnectionBad)

Secondly, I had to create a docker network that Traefik and other applications that will proxy through it will use:

docker network create traefik_default

Thirdly, I setup the applications in the docker-compose.yml file to use the same network that I just created:

version: "3"

services:
  app:
    build:
      context: .
      dockerfile: Dockerfile
    env_file:
      - .env
    environment:
      RAILS_ENV: ${RAILS_ENV}
      RACK_ENV: ${RACK_ENV}
      POSTGRES_USER: ${DATABASE_USER}
      POSTGRES_PASSWORD: ${DATABASE_PASSWORD}
      POSTGRES_DB: ${DATABASE_NAME}
      POSTGRES_HOST_AUTH_METHOD: ${DATABASE_HOST}
      POSTGRES_PORT: ${DATABASE_PORT}
    expose:
      - ${RAILS_PORT}
    networks:
      - traefik_default
    labels:
      - traefik.enable=true
      - traefik.http.routers.my_app.rule=Host(`${RAILS_HOST}`)
      - traefik.http.services.my_app.loadbalancer.server.port=${NGINX_PORT}
      - traefik.docker.network=traefik_default
    restart: always
    volumes:
      - .:/app
      - gem-cache:/usr/local/bundle/gems
      - node-modules:/app/node_modules
  web-server:
    build:
      context: .
      dockerfile: ./nginx/Dockerfile
    depends_on:
    - app
    expose:
      - ${NGINX_PORT}
    restart: always
    volumes:
      - .:/app
networks:
  traefik_default:
    external: true
volumes:
  gem-cache:
  node-modules:

Finally, in my .env file, I specified the private IP address of my host machine as the DATABASE_HOST as an environment variable this way:

DATABASE_NAME=my_app_development
DATABASE_USER=my-username
DATABASE_PASSWORD=passsword1
DATABASE_HOST=192.168.0.156
DATABASE_PORT=5432

RAILS_HOST=my_app.localhost
NGINX_PORT=80

RAILS_ENV=development
RACK_ENV=development
RAILS_MASTER_KEY=e879cbg21ff58a9c50933fe775a74d00
RAILS_PORT=3000