feat: Process experiment metadata in RC fetch response

Author: Athira M

common/api-review/remote-config.api.md

@@ -41,6 +41,7 @@ export function fetchConfig(remoteConfig: RemoteConfig): Promise<void>;
 export interface FetchResponse {
     config?: FirebaseRemoteConfigObject;
     eTag?: string;
+    experiments?: FirebaseExperimentDescription[];
     status: number;
     templateVersion?: number;
 }
@@ -51,6 +52,22 @@ export type FetchStatus = 'no-fetch-yet' | 'success' | 'failure' | 'throttle';
 // @public
 export type FetchType = 'BASE' | 'REALTIME';
 
+// @public
+export interface FirebaseExperimentDescription {
+    // (undocumented)
+    affectedParameterKeys?: string[];
+    // (undocumented)
+    experimentId: string;
+    // (undocumented)
+    experimentStartTime: string;
+    // (undocumented)
+    timeToLiveMillis: string;
+    // (undocumented)
+    triggerTimeoutMillis: string;
+    // (undocumented)
+    variantId: string;
+}
+
 // @public
 export interface FirebaseRemoteConfigObject {
     // (undocumented)

packages/remote-config/src/api.ts

@@ -102,6 +102,7 @@ export async function activate(remoteConfig: RemoteConfig): Promise<boolean> {
   if (
     !lastSuccessfulFetchResponse ||
     !lastSuccessfulFetchResponse.config ||
+    !lastSuccessfulFetchResponse.experiments ||
     !lastSuccessfulFetchResponse.eTag ||
     !lastSuccessfulFetchResponse.templateVersion ||
     lastSuccessfulFetchResponse.eTag === activeConfigEtag

packages/remote-config/src/client/rest_client.ts

@@ -18,7 +18,8 @@
 import {
   CustomSignals,
   FetchResponse,
-  FirebaseRemoteConfigObject
+  FirebaseRemoteConfigObject,
+  FirebaseExperimentDescription
 } from '../public_types';
 import {
   RemoteConfigFetchClient,
@@ -143,6 +144,7 @@ export class RestClient implements RemoteConfigFetchClient {
     let config: FirebaseRemoteConfigObject | undefined;
     let state: string | undefined;
     let templateVersion: number | undefined;
+    let experiments: FirebaseExperimentDescription[] | undefined;
 
     // JSON parsing throws SyntaxError if the response body isn't a JSON string.
     // Requesting application/json and checking for a 200 ensures there's JSON data.
@@ -158,6 +160,7 @@ export class RestClient implements RemoteConfigFetchClient {
       config = responseBody['entries'];
       state = responseBody['state'];
       templateVersion = responseBody['templateVersion'];
+      experiments = responseBody['experimentDescriptions'];
     }
 
     // Normalizes based on legacy state.
@@ -168,6 +171,7 @@ export class RestClient implements RemoteConfigFetchClient {
     } else if (state === 'NO_TEMPLATE' || state === 'EMPTY_CONFIG') {
       // These cases can be fixed remotely, so normalize to safe value.
       config = {};
+      experiments = [];
     }
 
     // Normalize to exception-based control flow for non-success cases.
@@ -180,6 +184,6 @@ export class RestClient implements RemoteConfigFetchClient {
       });
     }
 
-    return { status, eTag: responseEtag, config, templateVersion };
+    return { status, eTag: responseEtag, config, templateVersion, experiments };
   }
 }

packages/remote-config/src/public_types.ts

@@ -59,6 +59,32 @@ export interface FirebaseRemoteConfigObject {
   [key: string]: string;
 }
 
+/**
+ * Defines experiment and variant attached to a config parameter.
+ */
+export interface FirebaseExperimentDescription {
+  // A string of max length 22 characters and of format: _exp_<experiment_id>
+  experimentId: string;
+
+  // The variant of the experiment assigned to the app instance.
+  variantId: string;
+
+  // When the experiment was started.
+  experimentStartTime: string;
+
+  // How long the experiment can remain in STANDBY state. Valid range from 1 ms
+  // to 6 months.
+  triggerTimeoutMillis: string;
+
+  // How long the experiment can remain in ON state. Valid range from 1 ms to 6
+  // months.
+  timeToLiveMillis: string;
+
+  // A repeated of Remote Config parameter keys that this experiment is
+  // affecting the value of.
+  affectedParameterKeys?: string[];
+}
+
 /**
  * Defines a successful response (200 or 304).
  *
@@ -99,8 +125,12 @@ export interface FetchResponse {
    */
   templateVersion?: number;
 
-  // Note: we're not extracting experiment metadata until
-  // ABT and Analytics have Web SDKs.
+  /**
+   * A/B Test and Rollout experiment metadata.
+   * 
+   * <p>Only defined for 200 responses.
+   */
+  experiments?: FirebaseExperimentDescription[];
 }
 
 /**

packages/remote-config/test/api.test.ts

@@ -68,7 +68,14 @@ describe('Remote Config API', () => {
     status: 200,
     eTag: 'asdf',
     config: { 'foobar': 'hello world' },
-    templateVersion: 1
+    templateVersion: 1,
+    experiments: [{
+      experimentId: "_exp_1",
+      variantId : "1",
+      experimentStartTime : "2025-04-06T14:13:57.597Z",
+      triggerTimeoutMillis : "15552000000",
+      timeToLiveMillis : "15552000000"
+    }]
   };
   let fetchStub: sinon.SinonStub;
 
@@ -106,7 +113,8 @@ describe('Remote Config API', () => {
           Promise.resolve({
             entries: response.config,
             state: 'OK',
-            templateVersion: response.templateVersion
+            templateVersion: response.templateVersion,
+            experimentDescriptions: response.experiments,
           })
       } as Response)
     );

packages/remote-config/test/client/rest_client.test.ts

@@ -78,7 +78,14 @@ describe('RestClient', () => {
         eTag: 'etag',
         state: 'UPDATE',
         entries: { color: 'sparkling' },
-        templateVersion: 1
+        templateVersion: 1,
+        experimentDescriptions: [{
+          experimentId: "_exp_1",
+          variantId : "1",
+          experimentStartTime : "2025-04-06T14:13:57.597Z",
+          triggerTimeoutMillis : "15552000000",
+          timeToLiveMillis : "15552000000"
+        }]
       };
 
       fetchStub.returns(
@@ -90,7 +97,8 @@ describe('RestClient', () => {
             Promise.resolve({
               entries: expectedResponse.entries,
               state: expectedResponse.state,
-              templateVersion: expectedResponse.templateVersion
+              templateVersion: expectedResponse.templateVersion,
+              experimentDescriptions: expectedResponse.experimentDescriptions
             })
         } as Response)
       );
@@ -101,7 +109,8 @@ describe('RestClient', () => {
         status: expectedResponse.status,
         eTag: expectedResponse.eTag,
         config: expectedResponse.entries,
-        templateVersion: expectedResponse.templateVersion
+        templateVersion: expectedResponse.templateVersion,
+        experiments: expectedResponse.experimentDescriptions
       });
     });
 
@@ -191,7 +200,8 @@ describe('RestClient', () => {
         status: 304,
         eTag: 'response-etag',
         config: undefined,
-        templateVersion: undefined
+        templateVersion: undefined,
+        experiments: undefined
       });
     });
 
@@ -230,7 +240,8 @@ describe('RestClient', () => {
         status: 304,
         eTag: 'etag',
         config: undefined,
-        templateVersion: undefined
+        templateVersion: undefined,
+        experiments: undefined
       });
     });
 
@@ -248,7 +259,8 @@ describe('RestClient', () => {
           status: 200,
           eTag: 'etag',
           config: {},
-          templateVersion: undefined
+          templateVersion: undefined,
+          experiments: []
         });
       }
     });

packages/remote-config/test/remote_config.test.ts

@@ -391,6 +391,13 @@ describe('RemoteConfig', () => {
     const CONFIG = { key: 'val' };
     const NEW_ETAG = 'new_etag';
     const TEMPLATE_VERSION = 1;
+    const EXPERIMENTS = [{
+      "experimentId" : "_exp_1",
+      "variantId" : "1",
+      "experimentStartTime" : "2025-04-06T14:13:57.597Z",
+      "triggerTimeoutMillis" : "15552000000",
+      "timeToLiveMillis" : "15552000000"   
+    }];
 
     let getLastSuccessfulFetchResponseStub: sinon.SinonStub;
     let getActiveConfigEtagStub: sinon.SinonStub;
@@ -456,7 +463,8 @@ describe('RemoteConfig', () => {
         Promise.resolve({
           config: CONFIG,
           eTag: NEW_ETAG,
-          templateVersion: TEMPLATE_VERSION
+          templateVersion: TEMPLATE_VERSION,
+          experiments: EXPERIMENTS
         })
       );
       getActiveConfigEtagStub.returns(Promise.resolve(ETAG));
@@ -476,7 +484,8 @@ describe('RemoteConfig', () => {
         Promise.resolve({
           config: CONFIG,
           eTag: NEW_ETAG,
-          templateVersion: TEMPLATE_VERSION
+          templateVersion: TEMPLATE_VERSION,
+          experiments: EXPERIMENTS
         })
       );
       getActiveConfigEtagStub.returns(Promise.resolve());