110 lines
4.1 KiB
JavaScript
110 lines
4.1 KiB
JavaScript
import { isThrottlingError } from "@smithy/service-error-classification";
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export class DefaultRateLimiter {
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static setTimeoutFn = setTimeout;
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beta;
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minCapacity;
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minFillRate;
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scaleConstant;
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smooth;
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currentCapacity = 0;
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enabled = false;
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lastMaxRate = 0;
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measuredTxRate = 0;
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requestCount = 0;
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fillRate;
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lastThrottleTime;
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lastTimestamp = 0;
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lastTxRateBucket;
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maxCapacity;
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timeWindow = 0;
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constructor(options) {
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this.beta = options?.beta ?? 0.7;
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this.minCapacity = options?.minCapacity ?? 1;
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this.minFillRate = options?.minFillRate ?? 0.5;
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this.scaleConstant = options?.scaleConstant ?? 0.4;
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this.smooth = options?.smooth ?? 0.8;
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const currentTimeInSeconds = this.getCurrentTimeInSeconds();
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this.lastThrottleTime = currentTimeInSeconds;
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this.lastTxRateBucket = Math.floor(this.getCurrentTimeInSeconds());
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this.fillRate = this.minFillRate;
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this.maxCapacity = this.minCapacity;
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}
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getCurrentTimeInSeconds() {
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return Date.now() / 1000;
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}
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async getSendToken() {
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return this.acquireTokenBucket(1);
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}
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async acquireTokenBucket(amount) {
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if (!this.enabled) {
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return;
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}
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this.refillTokenBucket();
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if (amount > this.currentCapacity) {
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const delay = ((amount - this.currentCapacity) / this.fillRate) * 1000;
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await new Promise((resolve) => DefaultRateLimiter.setTimeoutFn(resolve, delay));
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}
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this.currentCapacity = this.currentCapacity - amount;
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}
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refillTokenBucket() {
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const timestamp = this.getCurrentTimeInSeconds();
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if (!this.lastTimestamp) {
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this.lastTimestamp = timestamp;
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return;
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}
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const fillAmount = (timestamp - this.lastTimestamp) * this.fillRate;
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this.currentCapacity = Math.min(this.maxCapacity, this.currentCapacity + fillAmount);
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this.lastTimestamp = timestamp;
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}
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updateClientSendingRate(response) {
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let calculatedRate;
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this.updateMeasuredRate();
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if (isThrottlingError(response)) {
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const rateToUse = !this.enabled ? this.measuredTxRate : Math.min(this.measuredTxRate, this.fillRate);
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this.lastMaxRate = rateToUse;
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this.calculateTimeWindow();
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this.lastThrottleTime = this.getCurrentTimeInSeconds();
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calculatedRate = this.cubicThrottle(rateToUse);
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this.enableTokenBucket();
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}
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else {
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this.calculateTimeWindow();
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calculatedRate = this.cubicSuccess(this.getCurrentTimeInSeconds());
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}
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const newRate = Math.min(calculatedRate, 2 * this.measuredTxRate);
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this.updateTokenBucketRate(newRate);
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}
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calculateTimeWindow() {
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this.timeWindow = this.getPrecise(Math.pow((this.lastMaxRate * (1 - this.beta)) / this.scaleConstant, 1 / 3));
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}
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cubicThrottle(rateToUse) {
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return this.getPrecise(rateToUse * this.beta);
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}
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cubicSuccess(timestamp) {
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return this.getPrecise(this.scaleConstant * Math.pow(timestamp - this.lastThrottleTime - this.timeWindow, 3) + this.lastMaxRate);
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}
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enableTokenBucket() {
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this.enabled = true;
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}
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updateTokenBucketRate(newRate) {
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this.refillTokenBucket();
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this.fillRate = Math.max(newRate, this.minFillRate);
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this.maxCapacity = Math.max(newRate, this.minCapacity);
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this.currentCapacity = Math.min(this.currentCapacity, this.maxCapacity);
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}
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updateMeasuredRate() {
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const t = this.getCurrentTimeInSeconds();
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const timeBucket = Math.floor(t * 2) / 2;
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this.requestCount++;
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if (timeBucket > this.lastTxRateBucket) {
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const currentRate = this.requestCount / (timeBucket - this.lastTxRateBucket);
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this.measuredTxRate = this.getPrecise(currentRate * this.smooth + this.measuredTxRate * (1 - this.smooth));
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this.requestCount = 0;
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this.lastTxRateBucket = timeBucket;
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}
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}
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getPrecise(num) {
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return parseFloat(num.toFixed(8));
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}
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}
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