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requestScheduler.js
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requestScheduler.js
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let axios = require("axios");
class RequestScheduler {
/**
* Create a RequestScheduler that sends performs web requests in line with a delay specified.
* @param {number} delay delay in ms
* @param {number} [priorityLevels=3] number of priority levels
*/
constructor(delay,priorityLevels = 3) {
this.delay = delay;
this.extraRequests = 0;
this.reqsRemaining = 120;
setInterval(() => {this.makeRequest()}, delay);
this.reqs = Array.from({length: 3}, () => []);
}
async makeRequest() {
if (this.extraRequests < 0) { //if the extra-requests system over-corrected
this.extraRequests++;
return;
}
let req = this.reqs.flat()[0]; //flatten this.reqs and grab the first one
if (req) {
this.reqs[req.priority].splice(this.reqs[req.priority].indexOf(req),1); //remove the req from the queue
if (this.reqs.flat().length > 0 && this.extraRequests > 1) { //check to see if we want to do it again
this.extraRequests--;
this.makeRequest();
}
try {
let axiosResp = await axios[req.method](req.url);
if (this.reqsRemaining == 0 || Number(axiosResp.headers["ratelimit-remaining"]) <= this.reqsRemaining) {
this.reqsRemaining = Number(axiosResp.headers["ratelimit-remaining"]);
this.extraRequests = Math.floor(this.reqsRemaining - axiosResp.headers["ratelimit-reset"] * 1000 / this.delay);
}
req.res(axiosResp); //request from the url and resolve the promise returned from .get with the data from the web request
} catch (err) {
req.timeout *= 2;
setTimeout(() => {
this.reqs[req.priority].push(req);
},req.timeout)
console.log("error requesting to url " + req.url)
}
}
}
/**
*
*/
async get(url,priority=0) { //make an axios-like request that adheres to the delay specified in the constructor
let resolutionFunction;
let promise = new Promise((res,rej) => { //make a promise to return
resolutionFunction = res; //put the resolution function into a wider scope
})
this.reqs[priority].push({
priority: priority,
method: "get",
url: url,
res: resolutionFunction,
timeout: 2000
})
return promise;
}
async getFirst(url,priority=0) { //same as get but unshift instead of push
let resolutionFunction;
let promise = new Promise((res,rej) => { //make a promise to return
resolutionFunction = res; //put the resolution function into a wider scope
})
this.reqs[priority].unshift({
priority: priority,
method: "get",
url: url,
res: resolutionFunction,
timeout: 2000
})
return promise;
}
}
exports.RequestScheduler = RequestScheduler;