Node.JS: Best way to handle max requests per minut

Question

I'm sorry if this question as already been answered and I hope I'm not breaking any SO rule, if so, in advance I apologise... I was wondering what was the best way to handle a request limiter? I've seen a bunch of throttles and rate-limiters online but I'm not sure how or if it could apply in my case.

I'm doing a bunch of [OUTGOING] request-promises based on an Array and on a server I can only make 90 request per minute. My request-promises are generated by this command: return Promise.all(array.map(request)).

I was thinking to handle it like this:

var i = 0;

return rp({
        url: uri,
        json: true,
      }).then((data) => {
        if (i <=90) {
          i ++;
          return data;
        } else {
          return i;
        }
      });

but I'm not sure if it will be a really effective way to handle it plus, I'm not sure how to handle the time relation yet... :S

Thanks in advance for your help and sorry I'm still a huge beginner...

Answer 1

Probably just do 90 requests per minute. You could use a pseudorecursive promise utilizing function:

function multiRequest(urls, maxPerMinute){
 return new Promise(function(cb){
   var result = [];
   //iterate recursively
   (function next(i){
     //if finished resolve promise
     if(i>=urls.length) return cb(result);
      //get all requests
      var requests = Promise.all(urls.slice(i,i+maxPerMinute).map(request));

      //if the requests are done, add them to result
      requests.then(data=>result.push(...data));        

      //if the requests + one minute done, conginue with next
      Promise.all([
        requests,
        new Promise(res=>setTimeout(res,1000*60))    
      ] ).then(_=>next(i+maxPerMinute))
 })(0);
 });
}

Use it like this:

 multiRequests(["google.com","stackoverflow.com"],90)
  .then(([google,so])=>...);

Answer 2

If the requests are started from different code parts, it might be useful to implement sth like a server queue which awaits the request until it is allowed to do so. The general handler:

var fromUrl = new Map();

function Server(url, maxPerMinute){
 if(fromUrl.has(url)) return fromUrl.get(url);
 fromUrl.set(url,this);

  this.tld = url;
  this.maxPerMinute = maxPerMinute;
  this.queue = [];
  this.running = false;

}


  Server.prototype ={
   run(d){
    if(this.running && !d) return;
    var curr = this.queue.shift();
    if(!curr){
      this.running = false;
      return;
    }
   var [url,resolve] = curr;
   Promise.all([
     request(this.tld + url),
     new Promise(res => setTimeout(res, 1000*60/this.maxPerMinute)
    ]).then(([res]) => {
       resolve(res);
       this.run(true);
    });
  },
  request(url){
   return new Promise(res => {
      this.queue.push([url,res]);
      this.run();
    });
  }
};

module.exports = Server;

Usable like this:

 var google = new require("server")("http://google.com");

google.maxPerMinute = 90;

google.request("/api/v3/hidden/service").then(res => ...);

Answer 3

You can use setInterval. Check out the documentation here.

var requestCount = 0;

setInterval(function(){
    // Every 60 seconds, reset the count
    requestCount = 0;
}, 60000);

// There needs to be an additional check before calling rp,
// that checks for requestCount > 90, and returns before starting the request.

rp({
    url: uri,
    json: true,
})
.then((data) => {
    requestCount++;
    return data;
});