update naming

Author: zhiyuanliang-ms

src/AzureAppConfigurationImpl.ts

@@ -62,7 +62,7 @@ import { FeatureFlagTracingOptions } from "./requestTracing/FeatureFlagTracingOp
 import { AIConfigurationTracingOptions } from "./requestTracing/AIConfigurationTracingOptions.js";
 import { KeyFilter, LabelFilter, SettingSelector } from "./types.js";
 import { ConfigurationClientManager } from "./ConfigurationClientManager.js";
-import { ETAG_LOOKUP_HEADER } from "./EtagUrlPipelinePolicy.js";
+import { CDN_TOKEN_LOOKUP_HEADER } from "./CdnTokenPipelinePolicy.js";
 import { getFixedBackoffDuration, getExponentialBackoffDuration } from "./common/backoffUtils.js";
 import { InvalidOperationError, ArgumentError, isFailoverableError, isInputError } from "./common/error.js";
 
@@ -507,7 +507,7 @@ export class AzureAppConfigurationImpl implements AzureAppConfiguration {
                     if (this.#isCdnUsed && selectorCollection.cdnToken) {
                         listOptions = {
                             ...listOptions,
-                            requestOptions: { customHeaders: { [ETAG_LOOKUP_HEADER]: selectorCollection.cdnToken }}
+                            requestOptions: { customHeaders: { [CDN_TOKEN_LOOKUP_HEADER]: selectorCollection.cdnToken }}
                         };
                     }
                     const pageEtags: string[] = [];
@@ -618,7 +618,7 @@ export class AzureAppConfigurationImpl implements AzureAppConfiguration {
                 // If CDN is used, add etag to request header so that the pipeline policy can retrieve and append it to the request URL
                 let getOptions: GetConfigurationSettingOptions = {};
                 if (this.#isCdnUsed && this.#kvSelectorCollection.cdnToken) {
-                    getOptions = { requestOptions: { customHeaders: { [ETAG_LOOKUP_HEADER]: this.#kvSelectorCollection.cdnToken } } };
+                    getOptions = { requestOptions: { customHeaders: { [CDN_TOKEN_LOOKUP_HEADER]: this.#kvSelectorCollection.cdnToken } } };
                 }
                 const response = await this.#getConfigurationSetting(sentinel, getOptions);
                 sentinel.etag = response?.etag;
@@ -680,7 +680,7 @@ export class AzureAppConfigurationImpl implements AzureAppConfiguration {
             if (this.#isCdnUsed && this.#kvSelectorCollection.cdnToken) {
                 // if CDN is used, add etag to request header so that the pipeline policy can retrieve and append it to the request URL
                 getOptions = {
-                    requestOptions: { customHeaders: { [ETAG_LOOKUP_HEADER]: this.#kvSelectorCollection.cdnToken ?? "" } },
+                    requestOptions: { customHeaders: { [CDN_TOKEN_LOOKUP_HEADER]: this.#kvSelectorCollection.cdnToken ?? "" } },
                 };
             }
             // send conditional request only when CDN is not used
@@ -754,7 +754,7 @@ export class AzureAppConfigurationImpl implements AzureAppConfiguration {
                     // If CDN is used, add etag to request header so that the pipeline policy can retrieve and append it to the request URL
                     listOptions = {
                         ...listOptions,
-                        requestOptions: { customHeaders: { [ETAG_LOOKUP_HEADER]: selectorCollection.cdnToken } }
+                        requestOptions: { customHeaders: { [CDN_TOKEN_LOOKUP_HEADER]: selectorCollection.cdnToken } }
                     };
                 }
 

src/CdnTokenPipelinePolicy.ts

@@ -0,0 +1,29 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT license.
+
+import { PipelinePolicy } from "@azure/core-rest-pipeline";
+
+export const CDN_TOKEN_LOOKUP_HEADER = "cdn-token-lookup";
+
+/**
+ * The pipeline policy that retrieves the CDN token from the request header and appends it to the request URL. After that the lookup header is removed from the request.
+ * @remarks
+ * The policy position should be perCall.
+ * The App Configuration service will not recognize the CDN token query parameter in the url, but this can help to break the CDN cache as the cache entry is based on the URL.
+ */
+export class CdnTokenPipelinePolicy implements PipelinePolicy {
+    name: string = "AppConfigurationCdnTokenPolicy";
+
+    async sendRequest(request, next) {
+        if (request.headers.has(CDN_TOKEN_LOOKUP_HEADER)) {
+            const token = request.headers.get(CDN_TOKEN_LOOKUP_HEADER);
+            request.headers.delete(CDN_TOKEN_LOOKUP_HEADER);
+
+            const url = new URL(request.url);
+            url.searchParams.append("_", token); // _ is a dummy query parameter to break the CDN cache
+            request.url = url.toString();
+        }
+
+        return next(request);
+    }
+}

src/EtagUrlPipelinePolicy.ts

@@ -6,7 +6,7 @@ import { AzureAppConfiguration } from "./AzureAppConfiguration.js";
 import { AzureAppConfigurationImpl } from "./AzureAppConfigurationImpl.js";
 import { AzureAppConfigurationOptions } from "./AzureAppConfigurationOptions.js";
 import { ConfigurationClientManager } from "./ConfigurationClientManager.js";
-import { EtagUrlPipelinePolicy } from "./EtagUrlPipelinePolicy.js";
+import { CdnTokenPipelinePolicy } from "./CdnTokenPipelinePolicy.js";
 import { instanceOfTokenCredential } from "./common/utils.js";
 import { ArgumentError } from "./common/error.js";
 
@@ -93,7 +93,7 @@ export async function loadFromCdn(
         // Add etag url policy to append etag to the request url for breaking CDN cache
         additionalPolicies: [
             ...(appConfigOptions.clientOptions?.additionalPolicies || []),
-            { policy: new EtagUrlPipelinePolicy(), position: "perCall" }
+            { policy: new CdnTokenPipelinePolicy(), position: "perCall" }
         ]
     };