[FSSDK-11965] add retry for cmab fetch

Author: raju-opti

lib/client_factory.ts

@@ -21,12 +21,13 @@ import { extractEventProcessor } from "./event_processor/event_processor_factory
 import { extractOdpManager } from "./odp/odp_manager_factory";
 import { extractVuidManager } from "./vuid/vuid_manager_factory";
 import { RequestHandler } from "./utils/http_request_handler/http";
-import { CLIENT_VERSION, DEFAULT_CMAB_CACHE_SIZE, DEFAULT_CMAB_CACHE_TIMEOUT, JAVASCRIPT_CLIENT_ENGINE } from "./utils/enums";
+import { CLIENT_VERSION, DEFAULT_CMAB_BACKOFF_MS, DEFAULT_CMAB_CACHE_SIZE, DEFAULT_CMAB_CACHE_TIMEOUT_MS, DEFAULT_CMAB_RETRIES, JAVASCRIPT_CLIENT_ENGINE } from "./utils/enums";
 import Optimizely from "./optimizely";
 import { DefaultCmabClient } from "./core/decision_service/cmab/cmab_client";
 import { CmabCacheValue, DefaultCmabService } from "./core/decision_service/cmab/cmab_service";
 import { InMemoryLruCache } from "./utils/cache/in_memory_lru_cache";
 import { transformCache, CacheWithRemove } from "./utils/cache/cache";
+import { ConstantBackoff, ExponentialBackoff } from "./utils/repeater/repeater";
 
 export type OptimizelyFactoryConfig = Config & {
   requestHandler: RequestHandler;
@@ -53,13 +54,17 @@ export const getOptimizelyInstance = (config: OptimizelyFactoryConfig): Optimize
 
   const cmabClient = new DefaultCmabClient({
     requestHandler,
+    retryConfig: {
+      maxRetries: DEFAULT_CMAB_RETRIES,
+      backoffProvider: () => new ConstantBackoff(DEFAULT_CMAB_BACKOFF_MS),
+    }
   });
 
   const cmabCache: CacheWithRemove<CmabCacheValue> = config.cmab?.cache ?
     transformCache(config.cmab.cache, (value) => JSON.parse(value), (value) => JSON.stringify(value)) :
     (() => {
       const cacheSize = config.cmab?.cacheSize || DEFAULT_CMAB_CACHE_SIZE;
-      const cacheTtl = config.cmab?.cacheTtl || DEFAULT_CMAB_CACHE_TIMEOUT;
+      const cacheTtl = config.cmab?.cacheTtl || DEFAULT_CMAB_CACHE_TIMEOUT_MS;
       return new InMemoryLruCache<CmabCacheValue>(cacheSize, cacheTtl);      
     })();
 

lib/utils/enums/index.ts

@@ -102,5 +102,7 @@ export const DECISION_MESSAGES = {
  */
 export const REQUEST_TIMEOUT_MS = 60 * 1000; // 1 minute
 
-export const DEFAULT_CMAB_CACHE_TIMEOUT = 30 * 60 * 1000; // 30 minutes
+export const DEFAULT_CMAB_CACHE_TIMEOUT_MS = 30 * 60 * 1000; // 30 minutes
 export const DEFAULT_CMAB_CACHE_SIZE = 1000;
+export const DEFAULT_CMAB_RETRIES = 1;
+export const DEFAULT_CMAB_BACKOFF_MS = 100; // 100 milliseconds

lib/utils/repeater/repeater.spec.ts

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 import { expect, vi, it, beforeEach, afterEach, describe } from 'vitest';
-import { ExponentialBackoff, IntervalRepeater } from './repeater';
+import { ConstantBackoff, ExponentialBackoff, IntervalRepeater } from './repeater';
 import { advanceTimersByTime } from '../../tests/testUtils';
 import { resolvablePromise } from '../promise/resolvablePromise';
 
@@ -88,6 +88,23 @@ describe("ExponentialBackoff", () => {
 });
 
 
+describe("ConstantBackoff", () => {
+  it("should always return the same backoff time", () => {
+    const constantBackoff = new ConstantBackoff(3000);
+    for(let i = 0; i < 5; i++) {
+      const time = constantBackoff.backoff();
+      expect(time).toEqual(3000);
+    }
+
+    // Reset to verify it still returns the same value
+    constantBackoff.reset();
+    for(let i = 0; i < 5; i++) {
+      const time = constantBackoff.backoff();
+      expect(time).toEqual(3000);
+    }
+  });
+});
+
 describe("IntervalRepeater", () => {
   beforeEach(() => {
     vi.useFakeTimers();

lib/utils/repeater/repeater.ts

@@ -63,6 +63,21 @@ export class ExponentialBackoff implements BackoffController {
   }
 }
 
+export class ConstantBackoff implements BackoffController {
+  private value: number;
+
+  constructor(value: number) {
+    this.value = value;
+  }
+
+  backoff(): number {
+    return this.value;
+  }
+  
+  reset(): void {
+  }
+}
+
 // IntervalRepeater is a Repeater that invokes the task at a fixed interval 
 // after the completion of the previous task invocation. If a backoff controller
 // is provided, the repeater will use the backoff controller to determine the