Rails 资产在 Heroku 上没有 Puma 的缓存控制标头答案

【问题标题】：Rails assets don't have Cache Control headers with Puma on HerokuRails 资产在 Heroku 上没有 Puma 的缓存控制标头
【发布时间】：2017-11-12 14:34:26
【问题描述】：

由于某种原因，当我使用 Puma 服务器从 Heroku 提供它们时，我的 Rails 资产不会发送缓存控制标头。

我在我的production.rb 中设置了config.public_file_server.headers = { 'Cache-Control' => 'public, max-age=172800' }，当我在本地机器上运行该应用程序时，一切正常：

Cache-Control: public, max-age=31536000
Etag: "fdffdae515ab907046e7deed6a567968ab3e689f8505a281988bf6892003ff92"
X-Request-Id: 065e704c-1bea-428c-9c40-3cd6b6e4330a
X-Runtime: 0.002411

但是，当我部署到 Heroku 时，我得到以下标头：

Server: Cowboy
Date: Sat, 10 Jun 2017 18:56:26 GMT
Content-Length: 0
Connection: keep-alive
strict-transport-security: max-age=15552000; includeSubDomains
Via: 1.1 vegur

这似乎有点奇怪，令人惊讶。我真的很不明白为什么会这样。我正在使用 Heroku 自己推荐的 Puma Web 服务器 - 这是我的 Procfile：

web: bundle exec puma -C config/puma.rb

这是我在配置中的 puma.rb：

# Puma can serve each request in a thread from an internal thread pool.
# The `threads` method setting takes two numbers a minimum and maximum.
# Any libraries that use thread pools should be configured to match
# the maximum value specified for Puma. Default is set to 5 threads for minimum
# and maximum, this matches the default thread size of Active Record.
#
threads_count = ENV.fetch("RAILS_MAX_THREADS") { 5 }.to_i
threads threads_count, threads_count

# Specifies the `port` that Puma will listen on to receive requests, default is 3000.
#
port        ENV.fetch("PORT") { 3000 }

# Specifies the `environment` that Puma will run in.
#
environment ENV.fetch("RAILS_ENV") { "development" }

# Specifies the number of `workers` to boot in clustered mode.
# Workers are forked webserver processes. If using threads and workers together
# the concurrency of the application would be max `threads` * `workers`.
# Workers do not work on JRuby or Windows (both of which do not support
# processes).

workers ENV.fetch("WEB_CONCURRENCY") {2}

# Use the `preload_app!` method when specifying a `workers` number.
# This directive tells Puma to first boot the application and load code
# before forking the application. This takes advantage of Copy On Write
# process behavior so workers use less memory. If you use this option
# you need to make sure to reconnect any threads in the `on_worker_boot`
# block.

preload_app!

# The code in the `on_worker_boot` will be called if you are using
# clustered mode by specifying a number of `workers`. After each worker
# process is booted this block will be run, if you are using `preload_app!`
# option you will want to use this block to reconnect to any threads
# or connections that may have been created at application boot, Ruby
# cannot share connections between processes.

on_worker_boot do
  ActiveRecord::Base.establish_connection if defined?(ActiveRecord)
end

# Allow puma to be restarted by `rails restart` command.
plugin :tmp_restart

有人有什么想法吗？顺便说一句，与this post 不同，所服务的文件是哪种文件类型没有任何区别——它们都没有设置缓存控制。

【问题讨论】：

标签： ruby-on-rails caching heroku cache-control puma

【解决方案1】：

找到问题了！

事实证明，如果 Heroku 没有明确告诉您，如果您想在资产管道中使用缓存，您需要将 rails_12factor gem 添加到您的 Gemfile：

group :production do
  gem 'rails_12factor'
end

只要我添加了rails_12factor gem，一切就开始正常了:)

【讨论】：

【解决方案2】：

使用 Rails 5，您可以简单地利用 ActionDispatch::Static 设置自定义 HTTP 标头来提供资产：

# config/environments/production.rb

config.public_file_server.headers = {
  'Cache-Control' => 'public, s-maxage=31536000, max-age=15552000',
  'Expires' => "#{1.year.from_now.to_formatted_s(:rfc822)}"
}

来源：https://blog.bigbinary.com/2015/10/31/rails-5-allows-setting-custom-http-headers-for-assets.html#rails-5-saves-the-day

【讨论】：