feat: assignment cache to dedupe logging by the precomputed client (#164)

* Add assignment cache to precomputed init methods

* Add test to confirm that it dedups assignment logging for the precomputedInit client

* Add test for offlinePrecomputedInit

* Switch test to useNonExpiringInMemoryAssignmentCache

* v3.9.8

* Update docs

Author: sameerank

docs/js-client-sdk.init.md

@@ -4,7 +4,7 @@
 
 ## init() function
 
-Initializes the Eppo client with configuration parameters. This method should be called once on application startup.
+Initializes the Eppo client with configuration parameters. This method should be called once on application startup. If an initialization is in process, calling `init` will return the in-progress `Promise<EppoClient>`<!-- -->. Once the initialization completes, calling `init` again will kick off the initialization routine (if `forceReinitialization` is `true`<!-- -->).
 
 **Signature:**
 

docs/js-client-sdk.md

@@ -120,7 +120,7 @@ Used to access a singleton SDK precomputed client instance. Use the method after
 
 </td><td>
 
-Initializes the Eppo client with configuration parameters. This method should be called once on application startup.
+Initializes the Eppo client with configuration parameters. This method should be called once on application startup. If an initialization is in process, calling `init` will return the in-progress `Promise<EppoClient>`<!-- -->. Once the initialization completes, calling `init` again will kick off the initialization routine (if `forceReinitialization` is `true`<!-- -->).
 
 
 </td></tr>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@eppo/js-client-sdk",
-  "version": "3.9.7",
+  "version": "3.9.8",
   "description": "Eppo SDK for client-side JavaScript applications",
   "main": "dist/index.js",
   "files": [

src/index.spec.ts

@@ -1282,6 +1282,8 @@ describe('EppoPrecomputedJSClient E2E test', () => {
   });
 
   it('logs assignments correctly', () => {
+    const mockAssignmentCache = td.object<AssignmentCache>();
+    globalClient.useCustomAssignmentCache(mockAssignmentCache);
     // Reset the mock logger before this test
     mockLogger = td.object<IAssignmentLogger>();
     globalClient.setAssignmentLogger(mockLogger);
@@ -1310,6 +1312,24 @@ describe('EppoPrecomputedJSClient E2E test', () => {
       format: 'PRECOMPUTED',
     });
   });
+
+  it('deduplicates assignment logging', () => {
+    // Reset the mock logger and assignment cache before this test
+    const mockLogger = td.object<IAssignmentLogger>();
+    globalClient.useNonExpiringInMemoryAssignmentCache();
+    globalClient.setAssignmentLogger(mockLogger);
+
+    expect(td.explain(mockLogger.logAssignment).callCount).toEqual(0);
+    globalClient.getStringAssignment('string-flag', 'default');
+    expect(td.explain(mockLogger.logAssignment).callCount).toEqual(1);
+    globalClient.getStringAssignment('string-flag', 'default');
+    expect(td.explain(mockLogger.logAssignment).callCount).toEqual(1);
+
+    expect(td.explain(mockLogger.logAssignment).calls[0]?.args[0]).toMatchObject({
+      featureFlag: 'string-flag',
+      subject: 'test-subject',
+    });
+  });
 });
 
 describe('offlinePrecomputedInit', () => {
@@ -1396,6 +1416,22 @@ describe('offlinePrecomputedInit', () => {
       { times: 1 },
     );
   });
+
+  it('deduplicates assignment logging', () => {
+    const client = offlinePrecomputedInit({
+      precomputedConfiguration,
+      assignmentLogger: mockLogger,
+    });
+    expect(td.explain(mockLogger.logAssignment).callCount).toBe(0);
+    client.getStringAssignment('string-flag', 'default');
+    expect(td.explain(mockLogger.logAssignment).callCount).toBe(1);
+    client.getStringAssignment('string-flag', 'default');
+    expect(td.explain(mockLogger.logAssignment).callCount).toBe(1);
+    expect(td.explain(mockLogger.logAssignment).calls[0]?.args[0]).toMatchObject({
+      subject: 'test-subject-key',
+      featureFlag: 'string-flag',
+    });
+  });
 });
 
 describe('EppoClient config', () => {

src/index.ts

@@ -694,6 +694,16 @@ export async function precomputedInit(
     skipInitialRequest = false,
   } = config;
 
+  // Add assignment cache initialization
+  const storageKeySuffix = buildStorageKeySuffix(apiKey);
+  const assignmentCache = assignmentCacheFactory({
+    chromeStorage: chromeStorageIfAvailable(),
+    storageKeySuffix,
+  });
+  if (assignmentCache instanceof HybridAssignmentCache) {
+    await assignmentCache.init();
+  }
+
   // Set up parameters for requesting updated configurations
   const requestParameters: PrecomputedFlagsRequestParameters = {
     apiKey,
@@ -724,6 +734,7 @@ export async function precomputedInit(
   if (config.banditLogger) {
     EppoPrecomputedJSClient.instance.setBanditLogger(config.banditLogger);
   }
+  EppoPrecomputedJSClient.instance.useCustomAssignmentCache(assignmentCache);
   await EppoPrecomputedJSClient.instance.fetchPrecomputedFlags();
 
   EppoPrecomputedJSClient.initialized = true;
@@ -804,6 +815,13 @@ export function offlinePrecomputedInit(
     };
 
     shutdownEppoPrecomputedClient();
+
+    // Add memory-only assignment cache for offline mode
+    const assignmentCache = assignmentCacheFactory({
+      storageKeySuffix: 'offline',
+      forceMemoryOnly: true,
+    });
+
     EppoPrecomputedJSClient.instance = new EppoPrecomputedJSClient({
       precomputedFlagStore: memoryOnlyPrecomputedStore,
       precomputedBanditStore: memoryOnlyPrecomputedBanditStore,
@@ -816,6 +834,7 @@ export function offlinePrecomputedInit(
     if (config.banditLogger) {
       EppoPrecomputedJSClient.instance.setBanditLogger(config.banditLogger);
     }
+    EppoPrecomputedJSClient.instance.useCustomAssignmentCache(assignmentCache);
   } catch (error) {
     applicationLogger.warn(
       '[Eppo SDK] Encountered an error initializing precomputed client, assignment calls will return the default value and not be logged',