构建简易Rails应用失败：rake等命令无法找到

问题概述 #

拉取极简Rails应用并修改后本地运行正常，但Docker构建时执行bundle exec rake assets:precompile报错找不到rake；注释该命令构建成功后，启动容器仍报rake缺失、无法加载rails组件；切换为Passenger启动后，又出现rack依赖缺失的错误。

关键报错信息 #

• rake缺失报错：

  bundler: failed to load command: rake (/minirails/vendor/bundle/ruby/2.7.0/bin/rake)         
  Gem::Exception: can't find executable rake for gem rake. rake is not currently included in the bundle, perhaps you meant to add it to your Gemfile?
  

• Passenger启动报错：

  App 97 output: Error: The application encountered the following error: cannot load such file -- rack (LoadError)
  

现有配置文件片段 #

Gemfile:

source 'https://rubygems.org'
git_source(:github) { |repo| "https://github.com/#{repo}.git" }

ruby '2.7.6'

gem 'rails', '~> 6.1'
gem 'sqlite3', '~> 1.4'
gem 'puma', '~> 4.1'
gem 'sass-rails', '>= 6'

group :development, :test do
  gem 'byebug', platforms: [:mri, :mingw, :x64_mingw]
end

group :development do
  gem 'listen', '~> 3.2'
end

Dockerfile核心步骤:

ADD Gemfile Gemfile.lock /minirails/
WORKDIR minirails
COPY ./ /minirails
RUN bundle config set deployment 'true'
RUN bundle config set without 'development test'
RUN bundle install

问题根源 #

1. 核心依赖缺失：Rails 6.x中rake默认属于development组依赖，Docker构建时通过without 'development test'排除了该组，导致production环境未安装rake；rack作为Rails核心依赖，若Gemfile.lock未包含production环境的完整依赖，也会出现缺失。
2. 构建顺序不合理：先添加Gemfile再复制整个项目，可能覆盖Gemfile/Gemfile.lock，且未利用Docker缓存，导致依赖安装基于不匹配的配置。
3. 启动脚本环境不兼容：原脚本未正确加载bundle环境，Passenger启动时未关联bundle安装的gem。

修复步骤 #

1. 调整Gemfile，确保核心依赖全局可用 #

在Gemfile中显式添加rake到全局（非分组），确保production环境能安装：

source 'https://rubygems.org'
git_source(:github) { |repo| "https://github.com/#{repo}.git" }

ruby '2.7.6'

gem 'rails', '~> 6.1'
gem 'sqlite3', '~> 1.4'
gem 'puma', '~> 4.1'
gem 'sass-rails', '>= 6'
gem 'rake' # 显式添加，确保production环境安装

group :development, :test do
  gem 'byebug', platforms: [:mri, :mingw, :x64_mingw]
end

group :development do
  gem 'listen', '~> 3.2'
end

本地执行bundle install更新Gemfile.lock，确保rake被纳入依赖列表。

2. 优化Docker构建流程 #

修改Dockerfile的文件复制顺序，优先处理Gemfile以利用缓存，避免文件覆盖：

FROM ruby:2.7.6-bullseye
LABEL maintainer="Me"

EXPOSE 3000
ENTRYPOINT ["/docker-entrypoint.sh"]

ENV PATH=/root/.yarn/bin:$PATH RAILS_ENV=production SECRET_KEY_BASE=c1f89d98........d47bc66fdcd417
ENV TZ=Europe/Berlin

# 合并系统依赖安装命令，减少分层
RUN apt-get update && apt-get upgrade -y && \
    apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 561F9B9CAC40B2F7 && \
    apt-get install -y apt-transport-https ca-certificates && \
    sh -c 'echo deb https://oss-binaries.phusionpassenger.com/apt/passenger bullseye main > /etc/apt/sources.list.d/passenger.list' && \
    apt-get update && apt-get install -y nginx-extras passenger curl certbot python3-certbot-nginx yarn nano cron tzdata && \
    ln -snf /usr/share/zoneinfo/$TZ /etc/localtime && echo $TZ > /etc/timezone

WORKDIR /minirails

# 先复制Gemfile相关文件，利用Docker缓存
COPY Gemfile Gemfile.lock ./

# 配置bundle并安装依赖
RUN bundle config --global silence_root_warning 1 && \
    bundle config set deployment 'true' && \
    bundle config set without 'development test' && \
    bundle install

# 复制项目其余文件
COPY ./ ./

RUN mkdir -p vendor
RUN echo "Rails.application.config.app_version = '$(date +%d.%m.%Y)'" > ./config/initializers/version.rb

# 取消注释预编译命令，此时rake已安装
RUN bundle exec rake assets:precompile

ADD ./docker-entrypoint.sh /

3. 修复启动脚本 #

修改docker-entrypoint.sh，确保bundle环境正确加载，推荐使用Rails默认的Puma服务器：

#!/usr/bin/env bash
set -e

# 执行数据库迁移
bundle exec rake db:migrate

# 启动Rails服务器，绑定0.0.0.0以支持外部访问
bundle exec rails server -b 0.0.0.0 -p 3000

若坚持使用Passenger，需添加--bundle-exec参数关联bundle依赖：

#!/usr/bin/env bash
set -e

bundle exec rake db:migrate
passenger start --port 3000 --environment production --bundle-exec

4. 调试验证 #

• 构建时添加RUN bundle list命令，查看已安装的gem，确认rake、rack、rails等核心组件存在；
• 启动容器前进入调试模式：

  docker run -it --entrypoint bash minirails
  

  在容器内执行bundle exec rake -v验证rake可用性，bundle exec rails -v验证rails命令是否正常。

内容的提问来源于stack exchange，提问作者MDickten