/*
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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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import { Constants, Logger } from "@azure/msal-common/node";
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import { ExponentialRetryStrategy } from "./ExponentialRetryStrategy.js";
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import { IHttpRetryPolicy } from "./IHttpRetryPolicy.js";
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const HTTP_STATUS_400_CODES_FOR_EXPONENTIAL_STRATEGY: Array<number> = [
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Constants.HTTP_NOT_FOUND,
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Constants.HTTP_REQUEST_TIMEOUT,
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Constants.HTTP_GONE,
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Constants.HTTP_TOO_MANY_REQUESTS,
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];
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const EXPONENTIAL_STRATEGY_NUM_RETRIES = 3;
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const LINEAR_STRATEGY_NUM_RETRIES = 7;
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const MIN_EXPONENTIAL_BACKOFF_MS: number = 1000;
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const MAX_EXPONENTIAL_BACKOFF_MS: number = 4000;
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const EXPONENTIAL_DELTA_BACKOFF_MS: number = 2000;
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const HTTP_STATUS_GONE_RETRY_AFTER_MS: number = 10 * 1000; // 10 seconds
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export class ImdsRetryPolicy implements IHttpRetryPolicy {
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/*
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* these are defined here as static variables despite being defined as constants outside of the
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* class because they need to be overridden in the unit tests so that the unit tests run faster
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*/
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static get MIN_EXPONENTIAL_BACKOFF_MS(): number {
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return MIN_EXPONENTIAL_BACKOFF_MS;
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}
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static get MAX_EXPONENTIAL_BACKOFF_MS(): number {
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return MAX_EXPONENTIAL_BACKOFF_MS;
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}
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static get EXPONENTIAL_DELTA_BACKOFF_MS(): number {
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return EXPONENTIAL_DELTA_BACKOFF_MS;
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}
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static get HTTP_STATUS_GONE_RETRY_AFTER_MS(): number {
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return HTTP_STATUS_GONE_RETRY_AFTER_MS;
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}
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public _isNewRequest: boolean;
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set isNewRequest(value: boolean) {
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this._isNewRequest = value;
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}
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private maxRetries: number;
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private exponentialRetryStrategy: ExponentialRetryStrategy =
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new ExponentialRetryStrategy(
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ImdsRetryPolicy.MIN_EXPONENTIAL_BACKOFF_MS,
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ImdsRetryPolicy.MAX_EXPONENTIAL_BACKOFF_MS,
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ImdsRetryPolicy.EXPONENTIAL_DELTA_BACKOFF_MS
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);
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/**
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* Pauses execution for a calculated delay before retrying a request.
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*
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* @param httpStatusCode - The HTTP status code of the response.
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* @param currentRetry - The current retry attempt number.
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* @param retryAfterHeader - The value of the "retry-after" header from the response.
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* @returns A promise that resolves to a boolean indicating whether a retry should be attempted.
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*/
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async pauseForRetry(
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httpStatusCode: number,
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currentRetry: number,
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logger: Logger
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): Promise<boolean> {
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if (this._isNewRequest) {
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this._isNewRequest = false;
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// calculate the maxRetries based on the status code, once per request
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this.maxRetries =
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httpStatusCode === Constants.HTTP_GONE
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? LINEAR_STRATEGY_NUM_RETRIES
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: EXPONENTIAL_STRATEGY_NUM_RETRIES;
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}
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/**
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* (status code is one of the retriable 400 status code
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* or
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* status code is >= 500 and <= 599)
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* and
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* current count of retries is less than the max number of retries
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*/
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if (
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(HTTP_STATUS_400_CODES_FOR_EXPONENTIAL_STRATEGY.includes(
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httpStatusCode
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) ||
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(httpStatusCode >= Constants.HTTP_SERVER_ERROR_RANGE_START &&
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httpStatusCode <= Constants.HTTP_SERVER_ERROR_RANGE_END &&
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currentRetry < this.maxRetries)) &&
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currentRetry < this.maxRetries
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) {
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const retryAfterDelay: number =
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httpStatusCode === Constants.HTTP_GONE
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? ImdsRetryPolicy.HTTP_STATUS_GONE_RETRY_AFTER_MS
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: this.exponentialRetryStrategy.calculateDelay(
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currentRetry
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);
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logger.verbose(
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`Retrying request in ${retryAfterDelay}ms (retry attempt: ${
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currentRetry + 1
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})`,
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""
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);
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// pause execution for the calculated delay
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await new Promise((resolve) => {
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return setTimeout(resolve, retryAfterDelay);
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});
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return true;
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}
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// if the status code is not retriable or max retries have been reached, do not retry
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return false;
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}
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}
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