服务器发事件(SSE)需要数据库操作时，Rails应用程序挂起

我正在学习&第一次在铁轨上做SSE！我的控制器代码:

I'm learning & doing SSE for the first time in rails! My controller code:

  def update
    response.headers['Content-Type'] = 'text/event-stream'
    sse = SSE.new(response.stream, event: 'notice')
    begin
      User.listen_to_creation do |user_id|
        sse.write({id: user_id})
      end
    rescue ClientDisconnected
    ensure
      sse.close
    end
  end

前端:

  var source = new EventSource('/site_update');
  source.addEventListener('notice', function(event) {
    var data = JSON.parse(event.data)
    console.log(data)
  });

模型发布/订阅

class User
  after_commit :notify_creation, on: :create

  def notify_creation
      ActiveRecord::Base.connection_pool.with_connection do |connection|
        self.class.execute_query(connection, ["NOTIFY user_created, '?'", id])
      end
  end

  def self.listen_to_creation
    ActiveRecord::Base.connection_pool.with_connection do |connection|
      begin
        execute_query(connection, ["LISTEN user_created"])
        connection.raw_connection.wait_for_notify do |event, pid, id|
          yield id
        end
      ensure
        execute_query(connection, ["UNLISTEN user_created"])
      end
    end
  end

  def self.clean_sql(query)
    sanitize_sql(query)
  end

  private

  def self.execute_query(connection, query)
    sql = self.clean_sql(query)
    connection.execute(sql)
  end
end

我注意到，如果我正在写SSE，就像在sse.write({time_now: Time.now})这样的教程中那样微不足道，那么一切都很好.在命令行中，CTRL+C成功关闭了本地服务器.

I've noticed that if I'm writing to SSE, something trivial like in a tutorial like... sse.write({time_now: Time.now}), everything works great. In command line, CTRL+C successfully shuts down the local server.

但是，每当我需要编写需要某种数据库操作的东西时，例如当我在进行postgres pub/sub时，例如

However, whenever I need to write something that requires some kind of database action, for example when I'm doing a postgres pub/sub as in this tutorial, then CTRL+C doesn't shut down the local server, it's just stuck and hangs and requires me to manually kill the PID.

在实际启动的服务器上，有时页面刷新也将永远挂起.其他时候，它将引发超时错误:

On the actual spun up server, sometimes a page refresh will hang forever as well. Other times, it will throw a timeout error:

ActiveRecord::ConnectionTimeoutError (could not obtain a connection from the pool within 5.000 seconds (waited 5.001 seconds); all pooled connections were in use):

不幸的是，这个问题在我使用Heroku的生产环境中也仍然存在.我只是收到很多超时错误.但是我想我已经正确配置了Heroku，还配置了本地设置……我的理解是，我只需要有一个较大的池(我有5)来拉连接并允许多个线程.在下面，您将找到一些配置代码.

Unfortunately this issue persists in production as well, where i'm using Heroku. I just get lots of timeout errors. But I think I have Heroku properly configured, and also local settings... my understanding is I just need to have a sizable pool (I have 5) to pull connections from and allow multiple threads. Below you'll find some config code.

没有环境变量，已使用默认值！

# config/database.yml
default: &default
  adapter: postgresql
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
  timeout: 5000

development:
  <<: *default
  database: proper_development


# config/puma.rb
workers Integer(ENV['WEB_CONCURRENCY'] || 1)

threads_count = Integer(ENV['MAX_THREADS'] || 5)
threads threads_count, threads_count

preload_app!

rackup      DefaultRackup
port        ENV['PORT']     || 3000
environment ENV['RACK_ENV'] || 'development'

on_worker_boot do
  # Worker specific setup for Rails 4.1+
  # See: https://devcenter.heroku.com/articles/deploying-rails-applications-with-the-puma-web-server#on-worker-boot
  ActiveRecord::Base.establish_connection
end

如果有帮助，这是我运行rails s

If it's helpful here's the output when I run rails s

=> Booting Puma
=> Rails 5.0.2 application starting in development on http://localhost:3000
=> Run `rails server -h` for more startup options
Puma starting in single mode...
* Version 4.3.3 (ruby 2.4.0-p0), codename: Mysterious Traveller
* Min threads: 0, max threads: 16
* Environment: development
* Listening on tcp://127.0.0.1:3000
* Listening on tcp://[::1]:3000
Use Ctrl-C to stop