问：

我正在使用 rails 5.1.0

我想创建同一应用程序的多个映像， 每个图像的域和数据库会有所不同，

image_1示例

• 域 example.app.com
• 数据库 - example_production

image_2示例

• 域 example1.app.com
• 数据库 - example1_production

image_3示例

• 域 example3.app.com
• 数据库 - example3_production

#application_controller.rb

class ApplicationRecord < ActiveRecord::Base
  self.abstract_class = true

  connects_to database: { writing: "#{request.base_url}_production", reading: "#{request.base_url}_production" }
end

语法 = docker/dockerfile：1.2

FROM ruby:2.3

RUN apt-get update -qq && apt-get install -y build-essential libpq-dev nodejs

# Set an environment variable where the Rails app is installed to inside of Docker image:
ENV RAILS_ROOT /var/www
RUN mkdir -p $RAILS_ROOT/app
RUN mkdir -p $RAILS_ROOT/shared
RUN mkdir -p $RAILS_ROOT/shared/tmp/sockets
RUN mkdir -p $RAILS_ROOT/shared/tmp/pids

# Set working directory, where the commands will be ran:
WORKDIR $RAILS_ROOT/app

# Setting env up
ENV RAILS_ENV='production'
ENV RACK_ENV='production'

COPY Gemfile Gemfile
COPY Gemfile.lock Gemfile.lock
RUN bundle install --jobs 20 --retry 5

# Adding project files
COPY . .
RUN ["chmod", "+x", "./docker-entrypoint.sh"]

EXPOSE 9292

ENTRYPOINT ["./docker-entrypoint.sh"]