限制事件驱动的Node.js HTTP请求

Question

I have a Node net.Server that listens to a legacy system on a TCP socket. When a message is received, it sends an http request to another http server. Simplified, it looks like this:

var request = require('request-promise');

...

socket.on('readable', function () {
  var msg = parse(socket.read());
  var postOptions = {
    uri: 'http://example.com/go',
    method: 'POST',
    json: msg,
    headers: {
      'Content-Type': 'application/json'
    }
  };

  request(postOptions);
})

The problem is that the socket is readable about 1000 times per second. The requests then overload the http server. Almost immediately, we get multiple-second response times.

In running Apache benchmark, it's clear that the http server can handle well over 1000 requests per second in under 100ms response time - if we limit the number of concurrent requests to about 100.

So my question is, what is the best way to limit the concurrent requests outstanding using the request-promise (by extension, request , and core.http.request ) library when each request is fired separately within an event callback?

Request's documentation says:

Note that if you are sending multiple requests in a loop and creating multiple new pool objects, maxSockets will not work as intended. To work around this, either use request.defaults with your pool options or create the pool object with the maxSockets property outside of the loop.

I'm pretty sure that this paragraph is telling me the answer to my problem, but I can't make sense of it. I've using defaults to limit the number of sockets open:

var rp = require('request-promise');
var request = rp.defaults({pool: {maxSockets: 50}});

Which doesn't help. My only thought at the moment is to manually manage a queue, but I expect that would be unnecessary if I only knew the conventional way to do it.

Answer 1

Well you need to throttle your request right? I have workaround this in two ways, but let me show you one patter I always use. I often use throttle-exec and Promise to make wrapper for request . You could install it with npm install throttle-exec and use Promise natively or third-party. Here is my gist for this wrapper https://gist.github.com/ans-4175/d7faec67dc6374803bbc

How do you use it? It's simple, just like ordinary request.

var Request = require("./Request")
Request({
    url:url_endpoint,
    json:param,
    method:'POST'
})
.then(function(result){
    console.log(result)
})
.catch(reject)

Tell me after you implement it. Either way I have another wrapper :)