I have a request-promise function that makes a request to an API. I'm rate-limited by this API and I keep getting the error message:
Exceeded 2 calls per second for api client. Reduce request rates to resume uninterrupted service.
I'm running a couple of Promise.each
loops in parallel which is causing the issue, if I run just one instance of Promise.each
everything runs fine. Within these Promise.each
calls they lead to the same function a with a request-promise call. I want to wrap this function with another queue
function and set the interval to 500
milliseconds so that a request
isn't made after one another, or parallel, but set to that time, on queue. The thing is I still need these promises to get their contents even if it takes a rather long time to get a response.
Is there anything that will do this for me? Something I can wrap a function in and it will respond at a set interval and not in parallel or fire functions one after another?
Update: Perhaps it does need to be promise specific, I tried to use underscore's throttle function
var debug = require("debug")("throttle")
var _ = require("underscore")
var request = require("request-promise")
function requestSite(){
debug("request started")
function throttleRequest(){
return request({
"url": "https://www.google.com"
}).then(function(response){
debug("request finished")
})
}
return _.throttle(throttleRequest, 100)
}
requestSite()
requestSite()
requestSite()
And all I got back was this:
$ DEBUG=* node throttle.js
throttle request started +0ms
throttle request started +2ms
throttle request started +0ms
Update
The last answer was wrong, this works but I still think I can do better:
// call fn at most count times per delay.
const debounce = function (fn, delay, count) {
let working = 0, queue = [];
function work() {
if ((queue.length === 0) || (working === count)) return;
working++;
Promise.delay(delay).tap(() => working--).then(work);
let {context, args, resolve} = queue.shift();
resolve(fn.apply(context, args));
}
return function debounced() {
return new Promise(resolve => {
queue.push({context: this, args: arguments, resolve});
if (working < count) work();
});
};
};
function mockRequest() {
console.log("making request");
return Promise.delay(Math.random() * 100);
}
var bounced = debounce(mockRequest, 800, 5);
for (var i = 0; i < 5; i++) bounced();
setTimeout(function(){
for (var i = 0; i < 20; i++) bounced();
},2000);
So you need to make the requests throttle function-wide - that's fine. Promises have queueing pretty much built in.
var p = Promise.resolve(); // our queue
function makeRequest(){
p = p.then(function(){ // queue the promise, wait for the queue
return request("http://www.google.com");
});
var p2 = p; // get a local reference to the promise
// add 1000 ms delay to queue so the next caller has to wait
p = p.delay(1000);
return p2;
};
Now makeRequest calls will be at least 1000ms apart.
jfriend has pointed out that you need two requests per second and not a single one - this is just as easily solvable with a second queue:
var p = Promise.resolve(1); // our first queue
var p2 = Promise.resolve(2); // our second queue
function makeRequest(){
var turn = Promise.any([p, p2]).then(function(val){
// add 1000 ms delay to queue so the next caller has to wait
// here we wait for the request too although that's not really needed,
// check both options out and decide which works better in your case
if(val === 1){
p = p.return(turn).delay(1, 1000);
} else {
p2 = p2.return(turn).delay(1, 1000);
}
return request("http://www.google.com");
});
return turn; // return the actual promise
};
This can be generalized to n
promises using an array similarly
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