Rails 服务器是否在主机“localhost”（127.0.0.1）上运行并接受端口 5432 上的 TCP/IP 连接？

Question

I'm building a rails app and I'm having trouble installing docker.

The build works, but when I try to create the DB with this command:

docker-compose run web bundle exec rails db:create

it throws this error:

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: Address not available
        Is the server running on host "localhost" (::1) and accepting
        TCP/IP connections on port 5432?

I've try to rename the host from localhost to db, it didn't work and I also tried to edit my etc/hosts.

docker-compose.yml

version: '3'
services:
  localhost:
    image: postgres
    volumes:
      - ./tmp/db:/var/lib/postgresql/data
  web:
    build: .
    command: bash -c "rm -f tmp/pids/server.pid && bundle exec rails s -p 3000 -b '0.0.0.0'"
    volumes:
      - .:/myapp
    ports:
      - "3000:3000"
    depends_on:
      - localhost
    working_dir: /myapp

Dockerfile

FROM ruby:2.6.2-alpine

RUN apk add --no-cache build-base postgresql-dev tzdata libxml2-dev libxslt-dev nodejs yarn

RUN mkdir /myapp
WORKDIR /myapp

COPY Gemfile /myapp/Gemfile
COPY Gemfile.lock /myapp/Gemfile.lock
COPY package.json /myapp/package.json

RUN gem install bundler:2.1.2
RUN bundle install

COPY . /myapp

RUN yarn install --check-files

database.yml

default: &default
  adapter: postgresql
  encoding: unicode
  host: localhost
  username: postgres
  password:
  # 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: myapp_development

/etc/hosts

# Host Database
#
# localhost is used to configure the loopback interface
# when the system is booting.  Do not change this entry.
##
127.0.0.1       localhost
255.255.255.255 broadcasthost
::1             localhost
# Added by Docker Desktop
# To allow the same kube context to work on the host and the container:
127.0.0.1 kubernetes.docker.internal
# End of section
127.0.0.1 postgres

How can I fix this issue? I'm not sure what I'm missing!

Answer 1

In Docker each "service" runs in its own container. So you would have the Rails app and the database in different containers. Each service is conceptually speaking a different server.

Your error ( Is the server running on host "localhost" (127.0.0.1).. ) suggests that your Rails application is looking for a database engine on the same machine. That DB is running on a separate server.

In a docker-compose file each service is addressable by its name. So change the connection string or setting in your Rails app from localhost to db or something.

Edit: I just now see that you named your DB server localhost , that's asking for trouble. Change that to db or something? :)