Add support for configuration cache using Web::Cache

docs/js-client-sdk.iclientconfigsync.configfetchedat.md

@@ -0,0 +1,11 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [@eppo/js-client-sdk](./js-client-sdk.md) &gt; [IClientConfigSync](./js-client-sdk.iclientconfigsync.md) &gt; [configFetchedAt](./js-client-sdk.iclientconfigsync.configfetchedat.md)
+
+## IClientConfigSync.configFetchedAt property
+
+**Signature:**
+
+```typescript
+configFetchedAt?: string;
+```

docs/js-client-sdk.iclientconfigsync.configpublishedat.md

@@ -0,0 +1,11 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [@eppo/js-client-sdk](./js-client-sdk.md) &gt; [IClientConfigSync](./js-client-sdk.iclientconfigsync.md) &gt; [configPublishedAt](./js-client-sdk.iclientconfigsync.configpublishedat.md)
+
+## IClientConfigSync.configPublishedAt property
+
+**Signature:**
+
+```typescript
+configPublishedAt?: string;
+```

docs/js-client-sdk.iclientconfigsync.md

@@ -72,6 +72,44 @@ IBanditLogger
 _(Optional)_
 
 
+</td></tr>
+<tr><td>
+
+[configFetchedAt?](./js-client-sdk.iclientconfigsync.configfetchedat.md)
+
+
+</td><td>
+
+
+</td><td>
+
+string
+
+
+</td><td>
+
+_(Optional)_
+
+
+</td></tr>
+<tr><td>
+
+[configPublishedAt?](./js-client-sdk.iclientconfigsync.configpublishedat.md)
+
+
+</td><td>
+
+
+</td><td>
+
+string
+
+
+</td><td>
+
+_(Optional)_
+
+
 </td></tr>
 <tr><td>
 

js-client-sdk.api.md

@@ -172,6 +172,10 @@ export interface IClientConfigSync {
     // (undocumented)
     banditLogger?: IBanditLogger;
     // (undocumented)
+    configFetchedAt?: string;
+    // (undocumented)
+    configPublishedAt?: string;
+    // (undocumented)
     enableOverrides?: boolean;
     // (undocumented)
     flagsConfiguration: Record<string, Flag | ObfuscatedFlag>;

package.json

@@ -62,5 +62,9 @@
     "@types/chrome": "^0.0.313",
     "@eppo/js-client-sdk-common": "4.15.1"
   },
-  "packageManager": "[email protected]+sha512.a6b2f7906b721bba3d67d4aff083df04dad64c399707841b7acf00f6b133b7ac24255f2652fa22ae3534329dc6180534e98d17432037ff6fd140556e2bb3137e"
+  "packageManager": "[email protected]+sha512.a6b2f7906b721bba3d67d4aff083df04dad64c399707841b7acf00f6b133b7ac24255f2652fa22ae3534329dc6180534e98d17432037ff6fd140556e2bb3137e",
+  "volta": {
+    "node": "22.18.0",
+    "yarn": "1.22.22"
+  }
 }

src/configuration-factory.spec.ts

@@ -55,6 +55,37 @@ describe('configurationStorageFactory', () => {
     expect(result).toBeInstanceOf(HybridConfigurationStore);
   });
 
+  it('is a HybridConfigurationStore with Web Cache API when hasWebCacheAPI is true', () => {
+    // Mock caches API
+    const mockCache = {
+      match: jest.fn(),
+      put: jest.fn(),
+    };
+    const mockCaches = {
+      open: jest.fn().mockResolvedValue(mockCache),
+      delete: jest.fn(),
+    };
+    global.caches = mockCaches;
+
+    const mockLocalStorage = {
+      clear: jest.fn(),
+      getItem: jest.fn(),
+      setItem: jest.fn(),
+      removeItem: jest.fn(),
+      key: jest.fn(),
+      length: 0,
+    };
+
+    const result = configurationStorageFactory(
+      { hasWebCacheAPI: true },
+      { windowLocalStorage: mockLocalStorage },
+    );
+    expect(result).toBeInstanceOf(HybridConfigurationStore);
+
+    // Clean up
+    delete global.caches;
+  });
+
   it('is a HybridConfigurationStore with a LocalStorageBackedAsyncStore persistentStore when window local storage is available', () => {
     const mockLocalStorage = {
       clear: jest.fn(),
@@ -72,6 +103,37 @@ describe('configurationStorageFactory', () => {
     expect(result).toBeInstanceOf(HybridConfigurationStore);
   });
 
+  it('prefers Web Cache API over localStorage when both are available', () => {
+    // Mock caches API
+    const mockCache = {
+      match: jest.fn(),
+      put: jest.fn(),
+    };
+    const mockCaches = {
+      open: jest.fn().mockResolvedValue(mockCache),
+      delete: jest.fn(),
+    };
+    global.caches = mockCaches;
+
+    const mockLocalStorage = {
+      clear: jest.fn(),
+      getItem: jest.fn(),
+      setItem: jest.fn(),
+      removeItem: jest.fn(),
+      key: jest.fn(),
+      length: 0,
+    };
+
+    const result = configurationStorageFactory(
+      { hasWebCacheAPI: true, hasWindowLocalStorage: true },
+      { windowLocalStorage: mockLocalStorage },
+    );
+    expect(result).toBeInstanceOf(HybridConfigurationStore);
+
+    // Clean up
+    delete global.caches;
+  });
+
   it('falls back to MemoryOnlyConfigurationStore when no persistence options are available', () => {
     const result = configurationStorageFactory({});
     expect(result).toBeInstanceOf(MemoryOnlyConfigurationStore);

src/configuration-factory.ts

@@ -12,13 +12,16 @@
 
 import ChromeStorageAsyncMap from './cache/chrome-storage-async-map';
 import { ChromeStorageEngine } from './chrome-storage-engine';
+import { ConfigurationAsyncStore } from './configuration-store';
 import {
   IsolatableHybridConfigurationStore,
   ServingStoreUpdateStrategy,
 } from './isolatable-hybrid.store';
 import { LocalStorageEngine } from './local-storage-engine';
 import { OVERRIDES_KEY } from './storage-key-constants';
+import { StorageMigration } from './storage-migration';
 import { StringValuedAsyncStore } from './string-valued.store';
+import { WebCacheStorageEngine } from './web-cache-storage-engine';
 
 export function precomputedFlagsStorageFactory(): IConfigurationStore<PrecomputedFlag> {
   return new MemoryOnlyConfigurationStore();
@@ -33,13 +36,15 @@
     maxAgeSeconds = 0,
     servingStoreUpdateStrategy = 'always',
     hasChromeStorage = false,
+    hasWebCacheAPI = false,
     hasWindowLocalStorage = false,
     persistentStore = undefined,
     forceMemoryOnly = false,
   }: {
     maxAgeSeconds?: number;
     servingStoreUpdateStrategy?: ServingStoreUpdateStrategy;
     hasChromeStorage?: boolean;
+    hasWebCacheAPI?: boolean;
     hasWindowLocalStorage?: boolean;
     persistentStore?: IAsyncStore<Flag>;
     forceMemoryOnly?: boolean;
@@ -73,6 +78,24 @@
       new StringValuedAsyncStore<Flag>(chromeStorageEngine, maxAgeSeconds),
       servingStoreUpdateStrategy,
     );
+  } else if (hasWebCacheAPI) {
+    // Web Cache API is available and preferred for better storage limits
+    // Run migration from localStorage to Cache API only if localStorage exists
+    if (windowLocalStorage) {
+      const migration = new StorageMigration(windowLocalStorage);
+      if (!migration.isMigrationCompleted()) {
+        migration.migrate().catch((error) =>
+          console.warn('Storage migration failed:', error),
+        );
+      }
+    }
+
+    const webCacheEngine = new WebCacheStorageEngine(storageKeySuffix ?? '');
+    return new IsolatableHybridConfigurationStore(
+      new MemoryStore<Flag>(),
+      new ConfigurationAsyncStore<Flag>(webCacheEngine, maxAgeSeconds),
+      servingStoreUpdateStrategy,
+    );
   } else if (hasWindowLocalStorage && windowLocalStorage) {
     // window.localStorage is available, use it as a fallback
     const localStorageEngine = new LocalStorageEngine(windowLocalStorage, storageKeySuffix ?? '');
@@ -135,3 +158,13 @@
 export function localStorageIfAvailable(): Storage | undefined {
   return hasWindowLocalStorage() ? window.localStorage : undefined;
 }
+
+/** Returns whether Web Cache API is available */
+export function hasWebCacheAPI(): boolean {
+  try {
+    return typeof caches !== 'undefined' && typeof caches.open === 'function';
+  } catch {
+    // Some environments may throw when accessing caches
+    return false;
+  }
+}

src/configuration-store.ts

@@ -0,0 +1,67 @@
+import { IAsyncStore } from '@eppo/js-client-sdk-common';
+
+/**
+ * Simplified storage engine interface for configuration data with built-in timestamps.
+ * Unlike IStringStorageEngine, this doesn't require separate metadata storage since
+ * configuration responses include createdAt timestamps.
+ */
+export interface IConfigurationStorageEngine {
+  getContentsJsonString: () => Promise<string | null>;
+  setContentsJsonString: (configurationJsonString: string) => Promise<void>;
+}
+
+/**
+ * Configuration store that works with storage engines optimized for configuration data.
+ * Uses the configuration response's built-in createdAt timestamp for expiration logic
+ * instead of maintaining separate metadata.
+ */
+export class ConfigurationAsyncStore<T> implements IAsyncStore<T> {
+  private initialized = false;
+
+  public constructor(
+    private storageEngine: IConfigurationStorageEngine,
+    private cooldownSeconds = 0,
+  ) {}
+
+  public isInitialized(): boolean {
+    return this.initialized;
+  }
+
+  public async isExpired(): Promise<boolean> {
+    if (!this.cooldownSeconds) {
+      return true;
+    }
+
+    try {
+      const contentsJsonString = await this.storageEngine.getContentsJsonString();
+      if (!contentsJsonString) {
+        return true;
+      }
+
+      const contents = JSON.parse(contentsJsonString);
+
+      // Check if this is a configuration response with createdAt
+      if (contents.createdAt) {
+        const createdAtMs = new Date(contents.createdAt).getTime();
+        return Date.now() - createdAtMs > this.cooldownSeconds * 1000;
+      }
+
+      // Fallback: if no createdAt, consider expired
+      return true;
+    } catch (error) {
+      console.warn('Failed to check expiration:', error);
+      return true;
+    }
+  }
+
+  public async entries(): Promise<Record<string, T>> {
+    const contentsJsonString = await this.storageEngine.getContentsJsonString();
+    return contentsJsonString ? JSON.parse(contentsJsonString) : {};
+  }
+
+  public async setEntries(entries: Record<string, T>): Promise<void> {
+    // Store the entire configuration response as-is
+    await this.storageEngine.setContentsJsonString(JSON.stringify(entries));
+    this.initialized = true;
+  }
+}

src/index.ts

@@ -37,6 +37,7 @@ import {
   chromeStorageIfAvailable,
   configurationStorageFactory,
   hasChromeStorage,
+  hasWebCacheAPI,
   hasWindowLocalStorage,
   localStorageIfAvailable,
   overrideStorageFactory,
@@ -330,6 +331,7 @@ export class EppoJSClient extends EppoClient {
           servingStoreUpdateStrategy: updateOnFetch,
           persistentStore,
           hasChromeStorage: hasChromeStorage(),
+          hasWebCacheAPI: hasWebCacheAPI(),
           hasWindowLocalStorage: hasWindowLocalStorage(),
         },
         {