How to limit API calls Per User? Leaky bucket algorithm

Question

I am trying to limit API calls on my app to shopify, the calls are limited at 2 calls each second for each user. I have a domain which i can use to identify each user but I'm trying to use a common node library to do this - I have already built the backend WITHOUT using the shopify official npm package so I am trying to accomplish it with a node library or with a manual bit of code, I really am unsure how I can identify the limits per domain value, I havent seen much resources for this strangely.

heres what it looks like and the library im using:

I'm trying to use this library:

https://www.npmjs.com/package/leaky-bucket

const LeakyBucket = require('leaky-bucket');


var bucket = new LeakyBucket({
     capacity: 2,          // items per interval, defaults to 60
     interval: 1,          // seconds, defaults to 60
     maxWaitingTime: 60
      // seconds, defaults to 300
});


var exports = module.exports = {

    getAllOrders: (req, res) => {
        const domain = req.params.domain;
        console.log(domain)
        bucket.throttle(function(domain) {
        db.getStoreTocken(domain, (result) => {
            const shopRequestUrl = 'https://' + domain + '/admin/orders.json';
            const shopRequestHeaders = { 'X-Shopify-Access-Token': result, };
            console.log(shopRequestUrl)
            console.log(result)
            request.get(shopRequestUrl, { headers: shopRequestHeaders }).then((shopResponse) => {
                res.status(200).end(shopResponse);
                console.log(shopResponse)           
            }).catch((error) => {
                res.status(error.statusCode).send(error.error.error_description);
            });     
        });
    })
    }

As you can see i parse the domain in this library although it doesnt mention anywhere it can identify it, can i add some domain identifier and mix it with this library or do i have to write my own code and somehow do it, OR just rewrite the damn thing with the official shopify library?

thanks very much if you can help.

Answer 1

You could create an object that holds a list of buckets per domain:

//buckets.js
const LeakyBucket = require('leaky-bucket');

let domains = {};
module.exports = (domain) => {
  if(domains[domain]) {
    return domains[domain]
   }
   domains[domain] = new LeakyBucket({
     capacity: 2,          // items per interval, defaults to 60
     interval: 1,          // seconds, defaults to 60
     maxWaitingTime: 60
      // seconds, defaults to 300
  });
  return domains[domain];
}

That way you create buckets per domain, at the expense of having a cache of buckets. I don't know if this fits your need and also beware that if you have 2 or more Node.js process running, each process will have a copy in memory of the buckets.