/*
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* Copyright (c) Microsoft Corporation. All rights reserved.
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* Licensed under the MIT License.
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*/
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export class ExponentialRetryStrategy {
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// Minimum backoff time in milliseconds
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private minExponentialBackoff: number;
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// Maximum backoff time in milliseconds
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private maxExponentialBackoff: number;
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// Maximum backoff time in milliseconds
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private exponentialDeltaBackoff: number;
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constructor(
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minExponentialBackoff: number,
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maxExponentialBackoff: number,
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exponentialDeltaBackoff: number
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) {
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this.minExponentialBackoff = minExponentialBackoff;
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this.maxExponentialBackoff = maxExponentialBackoff;
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this.exponentialDeltaBackoff = exponentialDeltaBackoff;
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}
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/**
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* Calculates the exponential delay based on the current retry attempt.
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*
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* @param {number} currentRetry - The current retry attempt number.
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* @returns {number} - The calculated exponential delay in milliseconds.
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*
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* The delay is calculated using the formula:
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* - If `currentRetry` is 0, it returns the minimum backoff time.
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* - Otherwise, it calculates the delay as the minimum of:
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* - `(2^(currentRetry - 1)) * deltaBackoff`
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* - `maxBackoff`
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*
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* This ensures that the delay increases exponentially with each retry attempt,
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* but does not exceed the maximum backoff time.
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*/
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public calculateDelay(currentRetry: number): number {
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// Attempt 1
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if (currentRetry === 0) {
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return this.minExponentialBackoff;
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}
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// Attempt 2+
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const exponentialDelay = Math.min(
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Math.pow(2, currentRetry - 1) * this.exponentialDeltaBackoff,
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this.maxExponentialBackoff
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);
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return exponentialDelay;
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}
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}
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