init project
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/*
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* Copyright 2019 gRPC authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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*/
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import { LogVerbosity } from './constants';
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import * as logging from './logging';
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const TRACER_NAME = 'backoff';
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const INITIAL_BACKOFF_MS = 1000;
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const BACKOFF_MULTIPLIER = 1.6;
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const MAX_BACKOFF_MS = 120000;
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const BACKOFF_JITTER = 0.2;
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/**
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* Get a number uniformly at random in the range [min, max)
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* @param min
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* @param max
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*/
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function uniformRandom(min: number, max: number) {
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return Math.random() * (max - min) + min;
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}
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export interface BackoffOptions {
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initialDelay?: number;
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multiplier?: number;
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jitter?: number;
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maxDelay?: number;
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}
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export class BackoffTimeout {
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/**
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* The delay time at the start, and after each reset.
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*/
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private readonly initialDelay: number = INITIAL_BACKOFF_MS;
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/**
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* The exponential backoff multiplier.
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*/
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private readonly multiplier: number = BACKOFF_MULTIPLIER;
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/**
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* The maximum delay time
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*/
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private readonly maxDelay: number = MAX_BACKOFF_MS;
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/**
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* The maximum fraction by which the delay time can randomly vary after
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* applying the multiplier.
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*/
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private readonly jitter: number = BACKOFF_JITTER;
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/**
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* The delay time for the next time the timer runs.
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*/
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private nextDelay: number;
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/**
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* The handle of the underlying timer. If running is false, this value refers
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* to an object representing a timer that has ended, but it can still be
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* interacted with without error.
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*/
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private timerId: NodeJS.Timeout;
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/**
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* Indicates whether the timer is currently running.
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*/
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private running = false;
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/**
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* Indicates whether the timer should keep the Node process running if no
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* other async operation is doing so.
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*/
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private hasRef = true;
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/**
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* The time that the currently running timer was started. Only valid if
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* running is true.
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*/
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private startTime: Date = new Date();
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/**
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* The approximate time that the currently running timer will end. Only valid
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* if running is true.
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*/
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private endTime: Date = new Date();
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private id: number;
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private static nextId = 0;
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constructor(private callback: () => void, options?: BackoffOptions) {
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this.id = BackoffTimeout.getNextId();
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if (options) {
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if (options.initialDelay) {
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this.initialDelay = options.initialDelay;
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}
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if (options.multiplier) {
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this.multiplier = options.multiplier;
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}
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if (options.jitter) {
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this.jitter = options.jitter;
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}
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if (options.maxDelay) {
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this.maxDelay = options.maxDelay;
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}
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}
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this.trace('constructed initialDelay=' + this.initialDelay + ' multiplier=' + this.multiplier + ' jitter=' + this.jitter + ' maxDelay=' + this.maxDelay);
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this.nextDelay = this.initialDelay;
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this.timerId = setTimeout(() => {}, 0);
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clearTimeout(this.timerId);
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}
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private static getNextId() {
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return this.nextId++;
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}
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private trace(text: string) {
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logging.trace(LogVerbosity.DEBUG, TRACER_NAME, '{' + this.id + '} ' + text);
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}
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private runTimer(delay: number) {
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this.trace('runTimer(delay=' + delay + ')');
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this.endTime = this.startTime;
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this.endTime.setMilliseconds(
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this.endTime.getMilliseconds() + delay
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);
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clearTimeout(this.timerId);
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this.timerId = setTimeout(() => {
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this.trace('timer fired');
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this.running = false;
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this.callback();
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}, delay);
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if (!this.hasRef) {
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this.timerId.unref?.();
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}
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}
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/**
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* Call the callback after the current amount of delay time
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*/
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runOnce() {
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this.trace('runOnce()');
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this.running = true;
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this.startTime = new Date();
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this.runTimer(this.nextDelay);
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const nextBackoff = Math.min(
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this.nextDelay * this.multiplier,
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this.maxDelay
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);
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const jitterMagnitude = nextBackoff * this.jitter;
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this.nextDelay =
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nextBackoff + uniformRandom(-jitterMagnitude, jitterMagnitude);
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}
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/**
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* Stop the timer. The callback will not be called until `runOnce` is called
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* again.
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*/
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stop() {
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this.trace('stop()');
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clearTimeout(this.timerId);
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this.running = false;
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}
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/**
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* Reset the delay time to its initial value. If the timer is still running,
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* retroactively apply that reset to the current timer.
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*/
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reset() {
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this.trace('reset() running=' + this.running);
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this.nextDelay = this.initialDelay;
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if (this.running) {
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const now = new Date();
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const newEndTime = this.startTime;
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newEndTime.setMilliseconds(newEndTime.getMilliseconds() + this.nextDelay);
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clearTimeout(this.timerId);
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if (now < newEndTime) {
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this.runTimer(newEndTime.getTime() - now.getTime());
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} else {
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this.running = false;
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}
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}
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}
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/**
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* Check whether the timer is currently running.
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*/
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isRunning() {
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return this.running;
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}
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/**
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* Set that while the timer is running, it should keep the Node process
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* running.
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*/
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ref() {
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this.hasRef = true;
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this.timerId.ref?.();
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}
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/**
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* Set that while the timer is running, it should not keep the Node process
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* running.
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*/
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unref() {
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this.hasRef = false;
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this.timerId.unref?.();
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}
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/**
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* Get the approximate timestamp of when the timer will fire. Only valid if
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* this.isRunning() is true.
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*/
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getEndTime() {
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return this.endTime;
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}
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}
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