ruby-on-rails - 如何在 Docker 中运行 Rails？ PG::ConnectionBad 无法将主机名 "pg"转换为地址:没有与主机名关联的地址

Question

我尝试按照此处的指南进行操作:https://docs.docker.com/compose/rails/

docker-compose.yml

version: '3'
services:
  pg:                                     ######### LOOK HERE!
    image: postgres
    volumes:
      - ./tmp/db:/var/lib/postgresql/data
  web:
    build: .
    command: bundle exec rails server -p 3000 -b '0.0.0.0'
    volumes:
      - .:/app
    ports:
      - "3000:3000"
    depends_on:
      - pg
    links:
      - pg                                     ######### LOOK HERE!
  cms:
    image: joomla
    restart: always
    links:
      - mysql:joomladb
    ports:
      - 8080:80
    environment:
      JOOMLA_DB_HOST: mysql
      JOOMLA_DB_PASSWORD: example
  mysql:
    image: mysql:5.6
    restart: always
    environment:
      MYSQL_ROOT_PASSWORD: example

config/database.yml

# SQLite version 3.x
#   gem install sqlite3
#
#   Ensure the SQLite 3 gem is defined in your Gemfile
#   gem 'sqlite3'
#
default: &default
  adapter: postgresql
  encoding: unicode
  pool: 5
  timeout: 5000
  host: pg                                     ######### LOOK HERE!
  username: postgres
  password:

development:
  <<: *default
  database: project

# Warning: The database defined as "test" will be erased and
# re-generated from your development database when you run "rake".
# Do not set this db to the same as development or production.
test:
  <<: *default
  database: project_test

production:
  <<: *default
  database: project

控制台

C:\Users\Chloe\workspace\project\src>docker-compose run web rake db:create
Starting src_pg_1 ... done
could not translate host name "pg" to address: No address associated with hostname
Couldn't create database for {"adapter"=>"postgresql", "encoding"=>"unicode", "pool"=>5, "timeout"=>5000, "host"=>"pg", "username"=>"postgres", "password"=>nil, "database"=>"project"}
rake aborted!
PG::ConnectionBad: could not translate host name "pg" to address: No address associated with hostname

docker-compose 版本 1.20.1，内部版本 5d8c71b2，Docker 版本 18.03.0-ce，内部版本 0520e24302

Answer 1

好的，我会尝试回答这个问题:

通常，当出现此错误时，可能意味着运行 db 容器返回了一些错误并停止了。

我遇到了同样的问题，经过一番挖掘后发现我有

LANG='en_US.UTF-8'
LANGUAGE='en_US:en'
LC_ALL='en_US.UTF-8'

在我的环境变量中设置，这导致db容器停止。因此，由于容器没有运行，我没有 db 主机。

这是我的 docker-compose.yml 文件的样子:

version: '3'

services:
  db:
    image: postgres
    volumes:
      - ./tmp/db:/var/lib/postgresql/data
    env_file: .env
  app:
    build: .
    command: bundle exec puma -p 3000 -C config/puma.rb
    env_file: .env
    volumes:
      - .:/app
    ports:
      - "3031:3000"
    depends_on:
      - db

这里是config/database.yml

default: &default
  adapter: postgresql
  encoding: unicode
  host: db
  pool: 5
  username: <%= ENV['POSTGRES_USER'] %>
  password: <%= ENV['POSTGRES_PASSWORD'] %>

development:
  <<: *default
  database: driggl_dev

test:
  <<: *default
  database: driggl_test

production:
  <<: *default
  database: driggl_prod

...以及用于开发的 .env 文件:

POSTGRES_USER=driggl
POSTGRES_PASSWORD=driggl

由于我有数据库数据的共享卷，因此为了确定起见，我从存储库中删除了 tmp/db 文件夹。

rm -rf tmp/*

然后我删除了所有容器和图像

docker rm $(docker ps -q -a) -f
docker rmi $(docker images -q) -f

最后我再次启动容器:

docker-compose up --build

一切终于顺利了。

摘要

1. 确保系统中某处没有缓存任何内容
2. 确保您的数据库容器在启动时不会返回错误。

我希望这会对遇到该问题的任何人有所帮助。