使用 Capistrano 来部署应用

使用 Capistrano 部署应用

前言

由于 Mina 一直以简单好用为著称，因此一直都是用 Mina 来部署应用。但是 Mina 也有局限性，之前的多机部署就遇到了难题，于是学习下如何用 Capistrano 来部署 Rails 应用

使用环境

  1. Capistrano 3.x
  2. Rails4.1
  3. Ruby2.0
  4. RVM

安装

在gemfile中添加支持的 gem

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group :development do
  gem 'capistrano'
  gem 'capistrano-bundler'
  gem 'capistrano-rails'
  gem 'capistrano-rvm'
end

初始化

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$ cap install

其中有几个比较重要的文件：

  1. Capfile用来配置Capistrano
  2. deploy.rb是一些共用task的定义
  3. production.rb / staging.rb用来定义具体的stage的tasks。

通过 cap -vT 可以查看当前可用的 task

配置

capfile

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# Load DSL and Setup Up Stages
require 'capistrano/setup'

# Includes default deployment tasks
require 'capistrano/deploy'

# 配置支持的插件
require 'capistrano/rvm'
require 'capistrano/bundler'
require 'capistrano/rails/assets'
require 'capistrano/rails/migrations'

# Loads custom tasks from `lib/capistrano/tasks' if you have any defined.
Dir.glob('lib/capistrano/tasks/*.rake').each { |r| import r }

deploy.rb

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# config valid only for Capistrano 3.1
lock '3.2.1'

set :application, 'student_lottery'
set :repo_url, 'git@bitbucket.org:linjunzhugg/student_lottery.git'

# Default branch is :master
# ask :branch, proc { `git rev-parse --abbrev-ref HEAD`.chomp }.call

# Default deploy_to directory is /var/www/my_app
set :deploy_to, '/home/deploy/student_lottery'

# Default value for :scm is :git
set :scm, :git

# Default value for :format is :pretty
# set :format, :pretty

# Default value for :log_level is :debug
# set :log_level, :debug

# Default value for :pty is false
# set :pty, true

# Default value for :linked_files is []
set :linked_files, %w{config/database.yml}

# Default value for linked_dirs is []
set :linked_dirs, %w{bin log tmp/pids tmp/cache tmp/sockets vendor/bundle public/system}

set :rvm_ruby_version, 'ruby-2.0.0-p481@rails4.0.4'

# Default value for default_env is {}
# set :default_env, { path: "/opt/ruby/bin:$PATH" }

# Default value for keep_releases is 5
# set :keep_releases, 5

namespace :deploy do

  desc 'Restart application'
  task :restart do
    on roles(:app), in: :sequence, wait: 5 do
      # Your restart mechanism here, for example:
      # execute :touch, release_path.join('tmp/restart.txt')
    end
  end

  # 就是这里插入的任务
  after :publishing, :restart

  after :restart, :clear_cache do
    on roles(:web), in: :groups, limit: 3, wait: 10 do
      # Here we can do anything such as:
      # within release_path do
      #   execute :rake, 'cache:clear'
      # end
    end
  end

end

config/production.rb

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set :branch, 'master'
# roles 的存在是方便我们针对某个 role 来执行相应的 task
server '192.168.0.13', user: 'deploy', roles: %w{app, web}
set :rails_env, :production

开始部署

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$ cap production deploy  # 开始部署

这时有人疑惑了，咦？这条命令的 task 在哪呢？我要如何定义自己的task 呢？

根据官方文档：一旦运行 cap production deploy ，就默认有以下这些任务：

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deploy:starting    - start a deployment, make sure everything is ready
deploy:started     - started hook (for custom tasks)
deploy:updating    - update server(s) with a new release
deploy:updated     - updated hook
deploy:publishing  - publish the new release
deploy:published   - published hook
deploy:finishing   - finish the deployment, clean up everything
deploy:finished    - finished hook

而我们之前在 capfile 中添加了以下的代码：

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# 配置支持的插件
require 'capistrano/rvm'
require 'capistrano/bundler'
require 'capistrano/rails/assets'
require 'capistrano/rails/migrations'

这些会自动在 starting updating 等任务中插入 before after 任务，例如：

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deploy
  deploy:starting
    [before]
      deploy:ensure_stage
      deploy:set_shared_assets
    deploy:check
  deploy:started
  deploy:updating
    git:create_release
    deploy:symlink:shared
  deploy:updated
    [before]
      deploy:bundle
    [after]
      deploy:migrate
      deploy:compile_assets
      deploy:normalize_assets
  deploy:publishing
    deploy:symlink:release
  deploy:published
  deploy:finishing
    deploy:cleanup
  deploy:finished
    deploy:log_revision

从中我们可以看到里面有 bundle migrate 等任务。

其他插件

比如 sidekiq 的自动重启，可以加上 capistrano-sidekiq gem