从 zmq 套接字返回值 [英] return value from zmq socket

问题描述

我正在使用 Socket.IO 让客户端网页从我的 Node.JS 服务器动态获取数据.在服务器端，我使用 zeromq 套接字库(REQ/REP 结构，请参阅 zguide 中的 rrclient.js 示例)将请求转发到 Python 后端.

I am using Socket.IO to have a client webpage fetch data dynamically from my Node.JS server. On the server-side, I am forwarding the request to a Python backend using the zeromq socket library (REQ/REP structure, see the rrclient.js example from zguide).

但是，由于我的服务器充当 socket.io 服务器，因此我必须按如下方式包装响应才能将其发送回特定客户端:

However, since my server is acting as the socket.io server, I have to wrap my response as follows in order to send it back to the specific client:

socket.on('app_request',function(appRequest){
      //route this request to the backend.
      var results = fetch_data(appRequest);
      //return it to the client
      socket.emit('app_results',results);
  });

因此 fetch_data 函数使用 zmq 套接字(socket.send)将请求推送到服务器.

so the fetch_data function uses a zmq socket (socket.send) to push a request to the server.

但是节点 ZMQ 套接字使用 socket.on('message',function(){}); 响应请求.listener 并且实际上不返回任何内容.

But the Node ZMQ socket responds to request using a socket.on('message',function(){}); listener and doesn't actually return anything.

如何使用 socket.on('message',function(){});向发起 socket.send() 请求的特定函数返回一个值?

换句话说，我怎样才能获得客户端的 socket.io 请求，让 Node.JS 使用 ZMQ 从 python 后端获取相关数据，然后将其返回给 socket.io 客户端?(当然以非阻塞方式)

In other words, how can I get a client's socket.io request to have Node.JS fetch relevant data from a python backend using ZMQ, then return it back to the socket.io client? (in a non-blocking fashion of course)

推荐答案

我做过类似的事情，你会想像这样重做；

I've done something similar, you'll want to rework it like so;

socket.on('app_request',function(appRequest){
  //route this request to the backend.
  fetch_data(appRequest, function(err, results) {
       socket.emit('app_results',results);
  });
});

zmq 是非阻塞的，因此在您将其发送到 socket.io 之前不会收到响应，使用此方法您可以调整 fetch_data 方法来存储回调，直到返回响应然后触发它.

zmq is non-blocking so the response is not received before your sending it down to socket.io, using this method you can adjust your fetch_data method to store the callback until the response is returned and then fire it.

粗略的 fetch_data 仅供参考，未测试；

Rough fetch_data for inspiration only not tested;

var zmq = require('zmq'),
    req = zmq.socket('req'),
    count = 0,
    jobs = {};


req.on('message', function(response) {
    var args  = JSON.parse(response),
        reply = args[0],
        id    = args[i];

    if (id && jobs[id]) {
         jobs[id].apply(null, Array.isArray(reply) ? reply : [reply]);

         delete jobs[id];
    }
}

function fetch_data(appRequest, callback) {
    var data = JSON.stringify([appRequest, count]);

    jobs[count] = callback;

    req.send(data);

    ++count;
}

然后在另一端解析 json 并保留 id 并将其与响应一起发回.

Then on the other side parse the json and keep the id and send it back with the response.

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