fix: Akamai data is fetched for the lifetime of the SDK connection

When the SDK retrieves data from the EdgeKV, it does so using a single
sub-request per call to `variation`, `variationDetail`, or
`allFlagsState`. The problem is that Akamai imposes a limit of 4
sub-requests per handler event.

If a customer evaluates more than 4 distinct flags during the handling
of a single event, subsequent flag lookups would fail. To combat this,
we now cache the flag values the first time an evaluation is requested,
and we keep that cache in memory for the full duration of the EdgeWorker
execution.

packages/shared/akamai-edgeworker-sdk/src/api/LDClient.ts

@@ -46,7 +46,6 @@ class LDClient extends LDClientImpl {
     defaultValue: LDFlagValue,
     callback?: (err: any, res: LDFlagValue) => void,
   ): Promise<LDFlagValue> {
-    await this._cacheableStoreProvider.prefetchPayloadFromOriginStore();
     return super.variation(key, context, defaultValue, callback);
   }
 
@@ -56,7 +55,6 @@ class LDClient extends LDClientImpl {
     defaultValue: LDFlagValue,
     callback?: (err: any, res: LDEvaluationDetail) => void,
   ): Promise<LDEvaluationDetail> {
-    await this._cacheableStoreProvider.prefetchPayloadFromOriginStore();
     return super.variationDetail(key, context, defaultValue, callback);
   }
 
@@ -65,7 +63,6 @@ class LDClient extends LDClientImpl {
     options?: LDFlagsStateOptions,
     callback?: (err: Error | null, res: LDFlagsState) => void,
   ): Promise<LDFlagsState> {
-    await this._cacheableStoreProvider.prefetchPayloadFromOriginStore();
     return super.allFlagsState(context, options, callback);
   }
 }

packages/shared/akamai-edgeworker-sdk/src/featureStore/cacheableStoreProvider.ts

@@ -2,14 +2,13 @@ import { EdgeProvider } from '.';
 
 /**
  * Wraps around an edge provider to cache a copy of the sdk payload locally an explicit request is made to refetch data from the origin.
- * The wrapper is neccessary to ensure that we dont make redundant sub-requests from Akamai to fetch an entire environment payload.
+ * The wrapper is necessary to ensure that we dona make redundant sub-requests from Akamai to fetch an entire environment payload.
  */
 export default class CacheableStoreProvider implements EdgeProvider {
   cache: string | null | undefined;
 
   constructor(
     private readonly _edgeProvider: EdgeProvider,
-    private readonly _rootKey: string,
   ) {}
 
   /**
@@ -24,16 +23,4 @@ export default class CacheableStoreProvider implements EdgeProvider {
 
     return this.cache;
   }
-
-  /**
-   * Invalidates cache and fetch environment payload data from origin. The result of this data is cached in memory.
-   * You should only call this function within a feature store to pre-fetch and cache payload data in environments
-   * where its expensive to make multiple outbound requests to the origin
-   * @param rootKey
-   * @returns
-   */
-  async prefetchPayloadFromOriginStore(rootKey?: string): Promise<string | null | undefined> {
-    this.cache = undefined; // clear the cache so that new data can be fetched from the origin
-    return this.get(rootKey || this._rootKey);
-  }
 }

packages/shared/akamai-edgeworker-sdk/src/index.ts

@@ -37,10 +37,7 @@ export const init = (params: BaseSDKParams): LDClient => {
 
   const logger = options.logger ?? BasicLogger.get();
 
-  const cachableStoreProvider = new CacheableStoreProvider(
-    featureStoreProvider,
-    buildRootKey(sdkKey),
-  );
+  const cachableStoreProvider = new CacheableStoreProvider(featureStoreProvider);
   const featureStore = new EdgeFeatureStore(cachableStoreProvider, sdkKey, 'Akamai', logger);
 
   const ldOptions: LDOptionsCommon = {