Docker: TCP/IP connections on port 5342? connect to server: Connection refused Is the server running on host

Question

I am using rails 3.0.0 with rails 7.

My dockerfile is as:

FROM ruby:3.0.0-alpine

RUN apk add --update --virtual \
    runtime-deps \
    postgresql-client\
    build-base \
    libxml2-dev \
    libxslt-dev \
    yarn \
    libffi-dev \
    readline \
    build-base \
    postgresql-dev \
    libc-dev \
    linux-headers \
    readline-dev \
    file \
    imagemagick \
    git \
    tzdata \
    && rm -rf /var/cache/apk*

WORKDIR /app
COPY . /app/
ENV BUNDLE_PATH /gems
RUN yarn install
RUN bundle install

ENTRYPOINT ["bin/rails"]
CMD ["s", "-b", "0.0.0.0"]

EXPOSE 3000

docker-compose.yml is as:

version: '3.8'
services:
  db:
    image: postgres:latest
    environment:
      - POSTGRES_PASSWORD=password
    ports:
      - "5433:5432"
    volumes:
      - "dbdata:/var/lib/postgresql/data"

  redis:
    image: redis:latest
    ports:
      - "6380:6379"

  web:
    build: .
    ports:
      - "3000:3000"
    depends_on:
      - db
      - redis
    environment:
      - DATABASE_URL=postgres://postgres:password@db:5433/postgres
      - REDIS_URL=redis://redis:6380
    volumes:
      - .:/app

volumes:
  dbdata:

database.yml file is as:

default: &default
  adapter: postgresql
  encoding: unicode
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
  port: 5432

development:
  <<: *default
  database: my_app_development
  username: postgres
  password: password

test:
  <<: *default
  database: my_app_test

#   production:
#     url: <%= ENV["MY_APP_DATABASE_URL"] %>

production:
  <<: *default
  database: my_app_production
  username: my_app
  password: <%= ENV["MY_APP_DATABASE_PASSWORD"] %>

using ubunut 20.04 LTS. getting error as: ActiveRecord::ConnectionNotEstablished could not connect to server: Connection refused Is the server running on host "172.22.0.3" and accepting TCP/IP connections on port 5433?

How to resolve this issue, any suggestion would help, thanks in advance.

Answer 1

reached to solution from above shared suggestions:

docker-compose.yml

 version: '3.8'
    services:
      db:
        image: postgres:latest
        environment:
          POSTGRES_PASSWORD: password
          command: -p 5000
          ports: "5000:5432"
        volumes:
          - "dbdata:/var/lib/postgresql/data"
    
      redis:
        image: redis:latest
        ports:
          - "6380:6379"
    
      web:
        build: .
        ports:
          - "3000:3000"
        depends_on:
          - db
          - redis
        environment:
          - DATABASE_URL=postgres://postgres:password@db:5432/postgres
          - REDIS_URL=redis://redis:6379
        volumes:
          - .:/app
    
    volumes:
      dbdata:

database.yml:

default: &default
  adapter: postgresql
  encoding: unicode
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>

development:
  <<: *default
  database: my_app_development
  username: postgres
  password: password

test:
  <<: *default
  database: my_app_test

#   production:
#     url: <%= ENV["MY_APP_DATABASE_URL"] %>

production:
  <<: *default
  database: my_app_production
  username: my_app
  password: <%= ENV["MY_APP_DATABASE_PASSWORD"] %>

Dockerfile:

FROM ruby:3.0.0-alpine

RUN apk add --update --virtual \
    runtime-deps \
    postgresql-client\
    build-base \
    libxml2-dev \
    libxslt-dev \
    yarn \
    libffi-dev \
    readline \
    build-base \
    postgresql-dev \
    libc-dev \
    linux-headers \
    readline-dev \
    file \
    imagemagick \
    git \
    tzdata \
    && rm -rf /var/cache/apk*

WORKDIR /app
COPY . /app/
ENV BUNDLE_PATH /gems
RUN yarn install
RUN bundle install

ENTRYPOINT ["bin/rails"]
CMD ["s", "-b", "0.0.0.0"]

EXPOSE 3000

Now with these configurations rails app is running. please update how to do it better, thanks.

Answer 2

Your web service is connecting with the db (postgresql) service using the internal docker network; when doing so, it connects directly to the IP address of the container, which (for postgresql) is listening on port 5432. Connections over the docker network does not require ports to be published / exposed, so the 5433:5432 port-mapping is not used for that.

I should add that your compose file is publishing (port-mapping) both the db and redis services; publishing them means that they'll be publicly accessible on the host's network interface (which, if you're not on an internal network, may be publicly accessible on the internet).

Make sure to only publish ports for services that must be publicly accessible (or are protected through other ways); as described above, connections between containers / services does not require those ports to be published.