试图从 Rails 上的 Ruby 连接到 postgres（在 docker 容器中）

Question

I am playing around with Docker and wanted to setup postgreSQL in a docker container and then connect to it from a (non dockerized) Ruby on Rails app. Here's the docker compose file - I am following this approach here .

version: "3"
services:
  db:
    image: "postgres:13"
    container_name: "postgres_dev"
    environment:
      POSTGRES_PASSWORD: "pgdev2021"
    ports:
      - "54320:5432"
    volumes:
      - pgdata://Users/thomas/Documents/Production/PostgreSQL/dbstorage

volumes:
  pgdata:

But when I then try to eg run "Rails db:prepare", I get this error:

rails aborted!
ActiveRecord::ConnectionNotEstablished: could not connect to server: No such file or directory
        Is the server running locally and accepting
        connections on Unix domain socket "/var/pgsql_socket/.s.PGSQL.54320"?
/Users/thomas/Documents/Websites/rails-frontend/bin/rails:5:in `<top (required)>'
/Users/thomas/Documents/Websites/rails-frontend/bin/spring:10:in `block in <top (required)>'
/Users/thomas/Documents/Websites/rails-frontend/bin/spring:7:in `<top (required)>'

Caused by:
PG::ConnectionBad: could not connect to server: No such file or directory
        Is the server running locally and accepting
        connections on Unix domain socket "/var/pgsql_socket/.s.PGSQL.54320"?
/Users/thomas/Documents/Websites/rails-frontend/bin/rails:5:in `<top (required)>'
/Users/thomas/Documents/Websites/rails-frontend/bin/spring:10:in `block in <top (required)>'
/Users/thomas/Documents/Websites/rails-frontend/bin/spring:7:in `<top (required)>'
Tasks: TOP => db:prepare
(See full trace by running task with --trace)

When I check, the container IS running

EDIT: database.yml

default: &default
  adapter: postgresql
  encoding: unicode
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
  port: 54320
  user: postgres

development:
  <<: *default
  database: db_development
test:
  <<: *default
  database: db_test
production:
  <<: *default
  database: db_production
  username: postgres
  password: <%= ENV['MY_DB_PASSWORD'] %>

Answer 1

If I want to start Postgres I always provide a user, password and initial db.

Are you trying to do inter-container networking or do you access from the host system? If it is intern-container networking, keep in mind by default the hostname of a service equals the service name.

Example compose file:

version: "3.9"
services:
  postgres:
    image: "postgres:13"
    container_name: "postgres_dev"
  ports:
    - 5432:5432
  environment:
    POSTGRES_USER: root
    POSTGRES_PASSWORD: password
    POSTGRES_DB: my-database

You can now connect with postgres:5432 from any other service specified in your docker-compose.yml . Or connect with http://localhost:5432 from your host machine. More about docker compose networking .

Verify by access the container and run something:

docker exec -it postgres_dev bash
psql -h localhost -p 5432 -U root -P password -d my-database