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// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT License. See License.txt in the project root for license information.
import {
BaseRequestPolicy,
RequestPolicy,
RequestPolicyOptionsLike,
RequestPolicyFactory,
} from "./requestPolicy";
import { WebResourceLike } from "../webResource";
import { HttpOperationResponse } from "../httpOperationResponse";
import { Constants } from "../util/constants";
import { delay } from "../util/utils";
const StatusCodes = Constants.HttpConstants.StatusCodes;
const DEFAULT_RETRY_COUNT = 3;
/**
* Options that control how to retry on response status code 429.
*/
export interface ThrottlingRetryOptions {
/**
* The maximum number of retry attempts. Defaults to 3.
*/
maxRetries?: number;
}
export function throttlingRetryPolicy(
maxRetries: number = DEFAULT_RETRY_COUNT
): RequestPolicyFactory {
return {
create: (nextPolicy: RequestPolicy, options: RequestPolicyOptionsLike) => {
return new ThrottlingRetryPolicy(nextPolicy, options, maxRetries);
},
};
}
/**
* To learn more, please refer to
* https://docs.microsoft.com/en-us/azure/azure-resource-manager/resource-manager-request-limits,
* https://docs.microsoft.com/en-us/azure/azure-subscription-service-limits and
* https://docs.microsoft.com/en-us/azure/virtual-machines/troubleshooting/troubleshooting-throttling-errors
*/
export class ThrottlingRetryPolicy extends BaseRequestPolicy {
private retryLimit: number;
constructor(nextPolicy: RequestPolicy, options: RequestPolicyOptionsLike, retryLimit: number) {
super(nextPolicy, options);
this.retryLimit = retryLimit;
}
public async sendRequest(httpRequest: WebResourceLike): Promise<HttpOperationResponse> {
return this._nextPolicy.sendRequest(httpRequest.clone()).then((response) => {
return this.retry(httpRequest, response, 0);
});
}
private async retry(
httpRequest: WebResourceLike,
httpResponse: HttpOperationResponse,
retryCount: number
): Promise<HttpOperationResponse> {
if (httpResponse.status !== StatusCodes.TooManyRequests) {
return httpResponse;
}
const retryAfterHeader: string | undefined = httpResponse.headers.get(
Constants.HeaderConstants.RETRY_AFTER
);
if (retryAfterHeader && retryCount < this.retryLimit) {
const delayInMs: number | undefined = ThrottlingRetryPolicy.parseRetryAfterHeader(
retryAfterHeader
);
if (delayInMs) {
await delay(delayInMs);
const res = await this._nextPolicy.sendRequest(httpRequest);
return this.retry(httpRequest, res, retryCount + 1);
}
}
return httpResponse;
}
public static parseRetryAfterHeader(headerValue: string): number | undefined {
const retryAfterInSeconds = Number(headerValue);
if (Number.isNaN(retryAfterInSeconds)) {
return ThrottlingRetryPolicy.parseDateRetryAfterHeader(headerValue);
} else {
return retryAfterInSeconds * 1000;
}
}
public static parseDateRetryAfterHeader(headerValue: string): number | undefined {
try {
const now: number = Date.now();
const date: number = Date.parse(headerValue);
const diff = date - now;
return Number.isNaN(diff) ? undefined : diff;
} catch (error) {
return undefined;
}
}
}