如何使 Rails.cache（内存缓存）与 Puma 一起工作？

Question

我正在使用 Rails 5.1。我在 Rails 中发生了应用程序范围的 memory_store 缓存。这是在我的 config/environments/development.rb 文件

中设置的

  £ Enable/disable caching. By default caching is disabled.
  if Rails.root.join('tmp/caching-dev.txt').exist?
    config.action_controller.perform_caching = true

    config.cache_store = :memory_store
    config.public_file_server.headers = {
      'Cache-Control' => 'public, max-age=172800'
    }
  else
    config.action_controller.perform_caching = true
    config.cache_store = :memory_store
  end

这让我可以做一些事情

      Rails.cache.fetch(cache_key) do
        msg_data
      end

在我的应用程序的一部分（网络套接字）中，并在我的应用程序的另一部分（控制器）中访问该数据。但是，我注意到的是，如果我用 puma 运行启动我的 Rails 服务器（例如，在 config/puma.rb 中包含以下文件）...

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 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") { 4 }

app_dir = File.expand_path("../..", __FILE__)
shared_dir = "£{app_dir}/shared"

£ Default to production
rails_env = ENV['RAILS_ENV'] || "production"
environment rails_env

£ Set up socket location
bind "unix://£{shared_dir}/sockets/puma.sock"

£ Logging
stdout_redirect "£{shared_dir}/log/puma.stdout.log", "£{shared_dir}/log/puma.stderr.log", true

£ Set master PID and state locations
pidfile "£{shared_dir}/pids/puma.pid"
state_path "£{shared_dir}/pids/puma.state"
activate_control_app





£ 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
  require "active_record"
  ActiveRecord::Base.connection.disconnect! rescue ActiveRecord::ConnectionNotEstablished
  ActiveRecord::Base.establish_connection(YAML.load_file("£{app_dir}/config/database.yml")[rails_env])
end

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

内存缓存不再有效。也就是说

Rails.cache.fetch(cache_key)

总是returns什么都没有。我想要一个多线程 puma 环境（最终）来优雅地处理许多请求。但是我也希望我的缓存能够工作。我怎样才能让他们一起玩？

Answer 1

我不知道你是否可以 - 但无论如何都不要那样做。使用真正的缓存服务。例如内存缓存。

http://guides.rubyonrails.org/caching_with_rails.html

config.cache_store = :mem_cache_store, "localhost" # assuming you run memcached on localhost

然后...就是这样。

Answer 2

您不能在集群模式下（即与多个 worker 一起）将 memory_store 与 puma 运行一起使用。它是这么说的right here in the Rails guide。您不能在不同的进程之间共享内存，所以这显然是有道理的。

如果将 puma workers 减少到 1 个不是一个选项，那么请考虑改用 Redis 或 Memcached。 Rails 指南中的文档在这方面非常完整 - 您需要向 Gemfile 添加一两个 gem，并更新 config.cache_store。您需要在盒子上安装相关服务，或者有很多托管服务提供商会为您管理它（Heroku Redis、Redis To Go、Memcachier 等）

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