@aws-amplify/core/src/clients/middleware/retry/amzSdkRequestHeaderMiddleware.ts

Core category of aws-amplify

// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0

import { HttpRequest, HttpResponse, Middleware } from '../../types';

import { RetryOptions } from './retryMiddleware';
import { AMZ_SDK_REQUEST_HEADER, DEFAULT_RETRY_ATTEMPTS } from './constants';

export type AmzSdkRequestHeaderMiddlewareOptions = Pick<
	RetryOptions,
	'maxAttempts'
>;

/**
 * Middleware injects `amz-sdk-request` header to indicate the retry state at the time an HTTP request is made.
 * This middleware should co-exist with retryMiddleware as it relies on the retryAttempts value in middleware context
 * set by the retry middleware.
 *
 * Example header: `amz-sdk-request: attempt=1; max=3`.
 *
 * This middleware is standalone because of extra headers may conflict with custom endpoint settings(e.g. CORS), we will
 * NOT use this middleware for API categories.
 */
export const amzSdkRequestHeaderMiddlewareFactory: Middleware<
	HttpRequest,
	HttpResponse,
	AmzSdkRequestHeaderMiddlewareOptions
> =
	({ maxAttempts = DEFAULT_RETRY_ATTEMPTS }) =>
	(next, context) => {
		return async function amzSdkRequestHeaderMiddleware(request) {
			const attemptsCount: number = context.attemptsCount ?? 0;
			request.headers[AMZ_SDK_REQUEST_HEADER] =
				`attempt=${attemptsCount + 1}; max=${maxAttempts}`;

			return next(request);
		};
	};