Capistrano的部署Rails应用程序 - 如何处理长迁移？ [英] Capistrano to deploy rails application - how to handle long migrations?

问题描述

所以我使用Capistrano的部署Rails应用程序到我的生产服务器（Apache +乘客），并在目前部署通常沿线有云：

So I am using Capistrano to deploy a rails application to my production server (apache+passenger) and at the moment deployment usually goes along the lines:

$cap deploy
$cap deploy:migrations

这让我想知道，比方说我的分贝：迁移花了很长的时间来生产服务器（DB模式的一大重构）上执行 - 在这种情况下，什么是Capistrano的最佳做法？如果用户在部署时连接到我的应用程序会发生什么？我应该摆好用户发送到静态预留页在数据库正在更新？是否Capistrano的自动的处理呢？我需要code一个配方，以帮助吗？还是轨/乘客的内部机制意味着我不必在所有担心这种特殊情况下？

It got me wondering, let's say my db:migrations took a long time to execute on the production server (a big refactor of the db schema) - in this case what is best practice with Capistrano? What happens if users are connected to my application at the time of deployment? Should I gracefully send users to a static placeholder page while the database is being updated? Does Capistrano handle this automagically? Do I need to code up a recipe to help with this? Or does the internal mechanisms of rails / passenger mean that I don't have to worry at all about this particular case?

感谢。

推荐答案

您应该如果应用程序不会是可用于同时提出了一个维护页面。我用这个Capistrano的任务：

You should put up a maintenance page if the application is not going to be available for a while. I use this Capistrano task:

namespace :deploy do
  namespace :web do
    desc <<-DESC
      Present a maintenance page to visitors. Disables your application's web \
      interface by writing a "maintenance.html" file to each web server. The \
      servers must be configured to detect the presence of this file, and if \
      it is present, always display it instead of performing the request.

      By default, the maintenance page will just say the site is down for \
      "maintenance", and will be back "shortly", but you can customize the \
      page by specifying the REASON and UNTIL environment variables:

        $ cap deploy:web:disable \\
              REASON="a hardware upgrade" \\
              UNTIL="12pm Central Time"

      Further customization will require that you write your own task.
    DESC
    task :disable, :roles => :web do
      require 'erb'
      on_rollback { run "rm #{shared_path}/system/maintenance.html" }

      reason = ENV['REASON']
      deadline = ENV['UNTIL']      
      template = File.read('app/views/admin/maintenance.html.erb')
      page = ERB.new(template).result(binding)

      put page, "#{shared_path}/system/maintenance.html", :mode => 0644
    end
  end
end

的应用程序/视图/管理/ maintenance.html.erb 文件应包含：

<p>We’re currently offline for <%= reason ? reason : 'maintenance' %> as of <%= Time.now.utc.strftime('%H:%M %Z') %>.</p>
<p>Sorry for the inconvenience. We’ll be back <%= deadline ? "by #{deadline}" : 'shortly' %>.</p>

最后一步是配置一些指令Apache的虚拟主机来寻找 maintenance.html 文件重定向到的所有请求，如果它是present：

The final step is to configure the Apache virtual host with some directives to look for the maintenance.html file and redirect all requests to it if it's present:

<IfModule mod_rewrite.c>
  RewriteEngine On

  # Redirect all requests to the maintenance page if present
  RewriteCond %{REQUEST_URI} !\.(css|gif|jpg|png)$
  RewriteCond %{DOCUMENT_ROOT}/system/maintenance.html -f
  RewriteCond %{SCRIPT_FILENAME} !maintenance.html
  RewriteRule ^.*$ /system/maintenance.html [L]
</IfModule>

要应用进入维护模式，运行上限部署：网址：禁用，并使其重新生活做上限部署：网络：启用。

To put the application into maintenance mode, run cap deploy:web:disable and to make it live again do cap deploy:web:enable.

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