Expiring bandit cache

Author: maya-the-mango

src/index.spec.ts

@@ -11,6 +11,7 @@ import {
 } from '@eppo/js-client-sdk-common';
 import { BanditParameters, BanditVariation } from '@eppo/js-client-sdk-common/dist/interfaces';
 import { ContextAttributes } from '@eppo/js-client-sdk-common/dist/types';
+import {Attributes} from "@eppo/js-client-sdk-common/src/types";
 import * as td from 'testdouble';
 
 import apiServer, { TEST_BANDIT_API_KEY, TEST_SERVER_PORT } from '../test/mockApiServer';
@@ -27,6 +28,8 @@ import {
 
 import { getInstance, IAssignmentEvent, IAssignmentLogger, init } from '.';
 
+import SpyInstance = jest.SpyInstance;
+
 const { DEFAULT_POLL_INTERVAL_MS, POLL_JITTER_PCT } = constants;
 
 describe('EppoClient E2E test', () => {
@@ -189,12 +192,12 @@ describe('EppoClient E2E test', () => {
     it('returns the default value when ufc config is absent', () => {
       const mockConfigStore = td.object<IConfigurationStore<Flag>>();
       td.when(mockConfigStore.get(flagKey)).thenReturn(null);
-      const client = new EppoClient(
-        mockConfigStore,
-        mockBanditVariationStore,
-        mockBanditModelStore,
-        requestParamsStub,
-      );
+      const client = new EppoClient({
+        flagConfigurationStore: mockConfigStore,
+        banditVariationConfigurationStore: mockBanditVariationStore,
+        banditModelConfigurationStore: mockBanditModelStore,
+        configurationRequestParameters: requestParamsStub,
+      });
       const assignment = client.getStringAssignment(flagKey, 'subject-10', {}, 'default-value');
       expect(assignment).toEqual('default-value');
     });
@@ -203,12 +206,12 @@ describe('EppoClient E2E test', () => {
       const mockConfigStore = td.object<IConfigurationStore<Flag>>();
       td.when(mockConfigStore.get(flagKey)).thenReturn(mockUfcFlagConfig);
       const subjectAttributes = { foo: 3 };
-      const client = new EppoClient(
-        mockConfigStore,
-        mockBanditVariationStore,
-        mockBanditModelStore,
-        requestParamsStub,
-      );
+      const client = new EppoClient({
+        flagConfigurationStore: mockConfigStore,
+        banditVariationConfigurationStore: mockBanditVariationStore,
+        banditModelConfigurationStore: mockBanditModelStore,
+        configurationRequestParameters: requestParamsStub,
+      });
       const mockLogger = td.object<IAssignmentLogger>();
       client.setAssignmentLogger(mockLogger);
       const assignment = client.getStringAssignment(
@@ -233,12 +236,12 @@ describe('EppoClient E2E test', () => {
       const mockConfigStore = td.object<IConfigurationStore<Flag>>();
       td.when(mockConfigStore.get(flagKey)).thenReturn(mockUfcFlagConfig);
       const subjectAttributes = { foo: 3 };
-      const client = new EppoClient(
-        mockConfigStore,
-        mockBanditVariationStore,
-        mockBanditModelStore,
-        requestParamsStub,
-      );
+      const client = new EppoClient({
+        flagConfigurationStore: mockConfigStore,
+        banditVariationConfigurationStore: mockBanditVariationStore,
+        banditModelConfigurationStore: mockBanditModelStore,
+        configurationRequestParameters: requestParamsStub,
+      });
       const mockLogger = td.object<IAssignmentLogger>();
       td.when(mockLogger.logAssignment(td.matchers.anything())).thenThrow(
         new Error('logging error'),
@@ -312,6 +315,131 @@ describe('EppoClient E2E test', () => {
       // Ensure that this test case correctly checked some test assignments
       expect(numAssignmentsChecked).toBeGreaterThan(0);
     });
+
+
+    describe('Bandit assignment cache', () => {
+      const flagKey = 'banner_bandit_flag'; // piggyback off a shared test data flag
+      const bobKey = 'bob';
+      const bobAttributes: Attributes = { age: 25, country: 'USA', gender_identity: 'female' };
+      const bobActions: Record<string, Attributes> = {
+        nike: { brand_affinity: 1.5, loyalty_tier: 'silver' },
+        adidas: { brand_affinity: -1.0, loyalty_tier: 'bronze' },
+        reebok: { brand_affinity: 0.5, loyalty_tier: 'gold' },
+      };
+
+      const aliceKey = 'alice';
+      const aliceAttributes: Attributes = {age: 25, country: 'USA', gender_identity: 'female' };
+      const aliceActions: Record<string, Attributes> = {
+        nike: { brand_affinity: 1.5, loyalty_tier: 'silver' },
+        adidas: {brand_affinity: -1.0, loyalty_tier: 'bronze' },
+        reebok: {brand_affinity: 0.5, loyalty_tier: 'gold' },
+      }
+      const charlieKey = 'charlie';
+      const charlieAttributes: Attributes = {age: 25, country: 'USA', gender_identity: 'female' };
+      const charlieActions: Record<string, Attributes> = {
+        nike: { brand_affinity: 1.0, loyalty_tier: 'gold' },
+        adidas: {brand_affinity: 1.0, loyalty_tier: 'silver' },
+        puma: {},
+      }
+
+      let banditLoggerSpy: SpyInstance<void, [banditEvent: IBanditEvent]>;
+      const defaultBanditCacheTTL = 600_000
+
+      beforeAll(async () => {
+        const dummyBanditLogger: IBanditLogger = {
+          logBanditAction(banditEvent: IBanditEvent) {
+            console.log(
+              `Bandit ${banditEvent.bandit} assigned ${banditEvent.subject} the action ${banditEvent.action}`,
+            );
+          },
+        };
+        banditLoggerSpy = jest.spyOn(dummyBanditLogger, 'logBanditAction');
+        await init({
+          apiKey: TEST_BANDIT_API_KEY, // Flag to dummy test server we want bandit-related files
+          baseUrl: `http://127.0.0.1:${TEST_SERVER_PORT}`,
+          assignmentLogger: mockLogger,
+          banditLogger: dummyBanditLogger,
+        });
+      });
+
+      it('Should not log bandit assignment if cached version is still valid', async () => {
+        const client = getInstance();
+        client.useExpiringInMemoryBanditAssignmentCache(2);
+
+        // Let's say someone is rage refreshing - we want to log assignment only once
+        for (const _ of Array(3).keys()) {
+          client.getBanditAction(
+            flagKey,
+            bobKey,
+            bobAttributes,
+            bobActions,
+            'default',
+          );
+        }
+        expect(banditLoggerSpy).toHaveBeenCalledTimes(1)
+      });
+      it('Should log bandit assignment if cached entry is expired', async () => {
+        jest.useFakeTimers();
+
+        const client = getInstance();
+        client.useExpiringInMemoryBanditAssignmentCache(2);
+
+        client.getBanditAction(
+          flagKey,
+          bobKey,
+          bobAttributes,
+          bobActions,
+          'default',
+        );
+        jest.advanceTimersByTime(defaultBanditCacheTTL);
+        client.getBanditAction(
+          flagKey,
+          bobKey,
+          bobAttributes,
+          bobActions,
+          'default',
+        );
+        expect(banditLoggerSpy).toHaveBeenCalledTimes(2)
+      })
+
+      it('Should invalidate least used cache entry if cache reaches max size', async () => {
+        const client = getInstance();
+        client.useExpiringInMemoryBanditAssignmentCache(2);
+
+        client.getBanditAction(
+          flagKey,
+          bobKey,
+          bobAttributes,
+          bobActions,
+          'default',
+        );
+        client.getBanditAction(
+          flagKey,
+          aliceKey,
+          aliceAttributes,
+          aliceActions,
+          'default',
+        );
+        client.getBanditAction(
+          flagKey,
+          charlieKey,
+          charlieAttributes,
+          charlieActions,
+          'default'
+        );
+        // even though bob was called 2nd time within cache validity time
+        // we expect assignment to be logged because max cache size is 2
+        // and currently storing alice and charlie
+        client.getBanditAction(
+          flagKey,
+          bobKey,
+          bobAttributes,
+          bobActions,
+          'default',
+        );
+        expect(banditLoggerSpy).toHaveBeenCalledTimes(4);
+      });
+    });
   });
 
   describe('initialization errors', () => {

src/index.ts

@@ -92,7 +92,7 @@ let clientInstance: EppoClient;
 export async function init(config: IClientConfig): Promise<EppoClient> {
   validation.validateNotBlank(config.apiKey, 'API key required');
 
-  const requestConfiguration: FlagConfigurationRequestParameters = {
+  const configurationRequestParameters: FlagConfigurationRequestParameters = {
     apiKey: config.apiKey,
     sdkName,
     sdkVersion,
@@ -110,12 +110,12 @@ export async function init(config: IClientConfig): Promise<EppoClient> {
   const banditVariationConfigurationStore = new MemoryOnlyConfigurationStore<BanditVariation[]>();
   const banditModelConfigurationStore = new MemoryOnlyConfigurationStore<BanditParameters>();
 
-  clientInstance = new EppoClient(
+  clientInstance = new EppoClient({
     flagConfigurationStore,
     banditVariationConfigurationStore,
     banditModelConfigurationStore,
-    requestConfiguration,
-  );
+    configurationRequestParameters,
+  });
   clientInstance.setAssignmentLogger(config.assignmentLogger);
   if (config.banditLogger) {
     clientInstance.setBanditLogger(config.banditLogger);