有一个聪明的方式给消息不同的优先级？ [英] Is there a clever way to give messages different priorities?

问题描述

我一直在想，我可以在与erlang进程交谈时，分配不同的消息不同的优先级。

我希望能够先处理高优先级的邮件，然后再优先处理一次。

我尝试过不同的方法，方法1：

  loop（） - > 
收到
 {high，Msg}  - > 
使用消息执行某些操作，
 loop（）
在0之后 - > 
 ok 
 end，
 receive 
 {low，Msg}  - > 
使用消息执行某些操作，
 loop（）
在0之后 - > 
 loop（）
结束。 
  

这样做是很安静的。我想接收者必须查看所有消息，看看每次运行时是否有一个高消息。

方法2：

我也尝试做一个调解器类型的方法，其中首先将消息设置为前台，前台，然后将消息发送到高队列或低队列，然后最后一个工作者线程请求firsk的高队列作业，如果该队列没有任何内容，那么从低队列中，如下所示：

这有缺点必须等待请求到达不同队列的前端，也许某种优先级系统可以工作： - ）

有更聪明的方式做这样的东西

解决方案

我认为这篇文章回答了你的问题：

https://www.erlang-solutions.com/upload/docs/9 /erlang11-nystrom.pdf

基本上你想收到如下：

 收到
 {hi_priority，Msg}  - >消息
 0  - > 
收到
 Msg  - > Msg 
 end 
 end 
  

由于Erlang的文档说0之后表示如果邮箱中没有匹配的（优先级）消息，则会立即发生超时。

我不知道有什么更聪明的方法：）

I've been thinking, I would like to able to assign different messages different priorities when talking to an erlang process.

I would like to be able to first handling high-priority messages, and then low-priority once.

I've tried different approaches, approach 1:

loop() ->
    receive 
        {high, Msg} ->
            Do something with the message, 
            loop()
        after 0 -> 
            ok
    end,
    receive 
        {low, Msg} ->
            Do something with the message, 
            loop()
        after 0 ->
            loop()
    end.

This does the job, but it is quiet slow. I guess the receive has to look through all the messages to see if there is a 'high' message everytime it runs.

Approach 2:

I've also tried doing a mediator type approach where a message was first set to a 'front-desk' the 'front-desk' then sent the message to either high-queue or low-queue, and then finally a 'worker' thread requested jobs from firsk the high-queue, and if that queue has nothing, then from the low-queue, as ilustrated here:

This had the downside of having to wait for the request to get to the front of the different queues, perhaps some sort of priority system would work :-)

Is there a smarter way of doing something like this?

解决方案

I think this paper answers your question:

https://www.erlang-solutions.com/upload/docs/9/erlang11-nystrom.pdf

Basically you want to have a receive as follows:

receive
  {hi_priority, Msg} -> Msg
after 0 ->
  receive
    Msg -> Msg
  end
end

As Erlang's documentation says "after 0" means that the timeout will occur immediately if there are no matching (priority) messages in the mailbox.

I am not aware of any smarter way of doing it:)

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