Fetch and store precomputed flags

Author: sameerank

src/api-endpoints.ts

@@ -1,4 +1,9 @@
-import { BASE_URL as DEFAULT_BASE_URL, UFC_ENDPOINT, BANDIT_ENDPOINT } from './constants';
+import {
+  BASE_URL as DEFAULT_BASE_URL,
+  UFC_ENDPOINT,
+  BANDIT_ENDPOINT,
+  PRECOMPUTED_FLAGS_ENDPOINT,
+} from './constants';
 import { IQueryParams } from './http-client';
 
 interface IApiEndpointsParams {
@@ -27,4 +32,8 @@ export default class ApiEndpoints {
   banditParametersEndpoint(): URL {
     return this.endpoint(BANDIT_ENDPOINT);
   }
+
+  precomputedFlagsEndpoint(): URL {
+    return this.endpoint(PRECOMPUTED_FLAGS_ENDPOINT);
+  }
 }

src/configuration-requestor.ts

@@ -1,8 +1,14 @@
 import { IConfigurationStore } from './configuration-store/configuration-store';
 import { IHttpClient } from './http-client';
-import { BanditVariation, BanditParameters, Flag, Environment } from './interfaces';
+import {
+  BanditVariation,
+  BanditParameters,
+  Flag,
+  Environment,
+  PrecomputedFlag,
+} from './interfaces';
 
-type Entry = Flag | BanditVariation[] | BanditParameters;
+type Entry = Flag | BanditVariation[] | BanditParameters | PrecomputedFlag;
 
 // Requests AND stores flag configurations
 export default class ConfigurationRequestor {
@@ -12,6 +18,7 @@ export default class ConfigurationRequestor {
     private readonly banditVariationConfigurationStore: IConfigurationStore<
       BanditVariation[]
     > | null,
+    private readonly precomputedFlagStore: IConfigurationStore<PrecomputedFlag>,
     private readonly banditModelConfigurationStore: IConfigurationStore<BanditParameters> | null,
   ) {}
 
@@ -91,4 +98,17 @@ export default class ConfigurationRequestor {
     });
     return banditVariationsByFlagKey;
   }
+
+  async fetchAndStorePrecomputedFlags(): Promise<void> {
+    const precomputedResponse = await this.httpClient.getPrecomputedFlags();
+    if (!precomputedResponse?.flags) {
+      return;
+    }
+
+    await this.hydrateConfigurationStore(this.precomputedFlagStore, {
+      entries: precomputedResponse.flags,
+      environment: precomputedResponse.environment,
+      createdAt: precomputedResponse.createdAt,
+    });
+  }
 }

src/constants.ts

@@ -7,6 +7,7 @@ export const DEFAULT_POLL_CONFIG_REQUEST_RETRIES = 7;
 export const BASE_URL = 'https://fscdn.eppo.cloud/api';
 export const UFC_ENDPOINT = '/flag-config/v1/config';
 export const BANDIT_ENDPOINT = '/flag-config/v1/bandits';
+export const PRECOMPUTED_FLAGS_ENDPOINT = '/flag-config/v1/precomputed';
 export const SESSION_ASSIGNMENT_CONFIG_LOADED = 'eppo-session-assignment-config-loaded';
 export const NULL_SENTINEL = 'EPPO_NULL';
 // number of logging events that may be queued while waiting for initialization

src/http-client.ts

@@ -45,6 +45,7 @@ export interface IPrecomputedFlagsResponse {
 export interface IHttpClient {
   getUniversalFlagConfiguration(): Promise<IUniversalFlagConfigResponse | undefined>;
   getBanditParameters(): Promise<IBanditParametersResponse | undefined>;
+  getPrecomputedFlags(): Promise<IPrecomputedFlagsResponse | undefined>;
   rawGet<T>(url: URL): Promise<T | undefined>;
 }
 
@@ -61,6 +62,11 @@ export default class FetchHttpClient implements IHttpClient {
     return await this.rawGet<IBanditParametersResponse>(url);
   }
 
+  async getPrecomputedFlags(): Promise<IPrecomputedFlagsResponse | undefined> {
+    const url = this.apiEndpoints.precomputedFlagsEndpoint();
+    return await this.rawGet<IPrecomputedFlagsResponse>(url);
+  }
+
   async rawGet<T>(url: URL): Promise<T | undefined> {
     try {
       // Canonical implementation of abortable fetch for interrupting when request takes longer than desired.