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Action Controller Live

将此模块混合到您的控制器中，该控制器中的所有操作都能够在写入时将数据流式传输到客户端。

class MyController < ActionController::Base
  include ActionController::Live

  def stream
    response.headers['Content-Type'] = 'text/event-stream'
    100.times {
      response.stream.write "hello world\n"
      sleep 1
    }
  ensure
    response.stream.close
  end
end

此模块有一些注意事项。您**不能**在响应已提交后写入标头（Response#committed? 将返回真值）。在响应流上调用write或close将导致响应对象被提交。确保在您的流上调用 write 或 close 之前设置所有标头。

您**必须**在完成时在您的流上调用 close，否则套接字可能会永远保持打开状态。

最后一个注意事项是您的操作在与主线程不同的线程中执行。确保您的操作是线程安全的，这应该没问题（不要跨线程共享状态等）。

请注意，Rails 默认情况下包含 Rack::ETag，它将缓冲您的响应。因此，流式响应可能无法与 Rack 2.2.x 正确配合，您可能需要在您的应用程序中实现变通方法。您可以设置ETag或Last-Modified响应标头，或者从中间件堆栈中删除Rack::ETag来解决此问题。

以下是如何在 Rack 版本为 2.2.x 时设置 Last-Modified 标头的示例

def stream
  response.headers["Content-Type"] = "text/event-stream"
  response.headers["Last-Modified"] = Time.now.httpdate # Add this line if your Rack version is 2.2.x
  ...
end
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类公共方法

live_thread_pool_executor()

来源：显示 | 在 GitHub 上

# File actionpack/lib/action_controller/metal/live.rb, line 385
def self.live_thread_pool_executor
  @live_thread_pool_executor ||= Concurrent::CachedThreadPool.new(name: "action_controller.live")
end

实例公共方法

process(name)

来源：显示 | 在 GitHub 上

# File actionpack/lib/action_controller/metal/live.rb, line 276
def process(name)
  t1 = Thread.current
  locals = t1.keys.map { |key| [key, t1[key]] }

  error = nil
  # This processes the action in a child thread. It lets us return the response
  # code and headers back up the Rack stack, and still process the body in
  # parallel with sending data to the client.
  new_controller_thread {
    ActiveSupport::Dependencies.interlock.running do
      t2 = Thread.current

      # Since we're processing the view in a different thread, copy the thread locals
      # from the main thread to the child thread. :'(
      locals.each { |k, v| t2[k] = v }
      ActiveSupport::IsolatedExecutionState.share_with(t1)

      begin
        super(name)
      rescue => e
        if @_response.committed?
          begin
            @_response.stream.write(ActionView::Base.streaming_completion_on_exception) if request.format == :html
            @_response.stream.call_on_error
          rescue => exception
            log_error(exception)
          ensure
            log_error(e)
            @_response.stream.close
          end
        else
          error = e
        end
      ensure
        # Ensure we clean up any thread locals we copied so that the thread can reused.
        ActiveSupport::IsolatedExecutionState.clear
        locals.each { |k, _| t2[k] = nil }

        @_response.commit!
      end
    end
  }

  ActiveSupport::Dependencies.interlock.permit_concurrent_loads do
    @_response.await_commit
  end

  raise error if error
end

response_body=(body)

来源：显示 | 在 GitHub 上

# File actionpack/lib/action_controller/metal/live.rb, line 326
def response_body=(body)
  super
  response.close if response
end

send_stream(filename:, disposition: "attachment", type: nil)

将流发送到浏览器，这在您生成导出或其他运行数据时很有用，您不希望将整个文件首先缓存在内存中。类似于 send_data，但数据是实时生成的。

选项：* :filename - 为浏览器建议使用的文件名。* :type - 指定 HTTP 内容类型。您可以指定字符串或使用Mime::Type.register注册的类型的符号，例如：json。如果省略，类型将从:filename中指定的文件扩展名推断出来。如果未为扩展名注册内容类型，则将使用默认类型“application/octet-stream”。* :disposition - 指定文件将内联显示还是下载。有效值为“inline”和“attachment”（默认值）。

生成 csv 导出的示例

send_stream(filename: "subscribers.csv") do |stream|
  stream.write "email_address,updated_at\n"

  @subscribers.find_each do |subscriber|
    stream.write "#{subscriber.email_address},#{subscriber.updated_at}\n"
  end
end

来源：显示 | 在 GitHub 上

# File actionpack/lib/action_controller/metal/live.rb, line 355
def send_stream(filename:, disposition: "attachment", type: nil)
  payload = { filename: filename, disposition: disposition, type: type }
  ActiveSupport::Notifications.instrument("send_stream.action_controller", payload) do
    response.headers["Content-Type"] =
      (type.is_a?(Symbol) ? Mime[type].to_s : type) ||
      Mime::Type.lookup_by_extension(File.extname(filename).downcase.delete("."))&.to_s ||
      "application/octet-stream"

    response.headers["Content-Disposition"] =
      ActionDispatch::Http::ContentDisposition.format(disposition: disposition, filename: filename)

    yield response.stream
  end
ensure
  response.stream.close
end