chore: confirm getPrecomputedAssignments functionality in node (#89)

* Add test for getPrecomputedAssignments

* Update common dependency version again

* Move precomputed test above bandits tests

* Monkey patch getPrecomputedConfiguration

* Allow salt to be an empty string if provided by the user

* Update common sdk dependency

* Fix lint warnings

* v3.7.0-alpha.0

Author: sameerank

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@eppo/node-server-sdk",
-  "version": "3.6.2",
+  "version": "3.7.0-alpha.0",
   "description": "Eppo node server SDK",
   "main": "dist/index.js",
   "files": [
@@ -29,7 +29,7 @@
   },
   "homepage": "https://github.com/Eppo-exp/node-server-sdk#readme",
   "dependencies": {
-    "@eppo/js-client-sdk-common": "^4.6.3"
+    "@eppo/js-client-sdk-common": "4.8.0-alpha.1"
   },
   "devDependencies": {
     "@google-cloud/storage": "^6.9.3",

src/index.spec.ts

@@ -8,10 +8,14 @@ import {
   VariationType,
   IBanditEvent,
   IBanditLogger,
+  IConfigurationWire,
+  ContextAttributes,
+  Attributes,
+  decodePrecomputedFlag,
+  BanditParameters,
+  BanditVariation,
 } 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 base64 from 'js-base64';
 import * as td from 'testdouble';
 
 import apiServer, { TEST_BANDIT_API_KEY, TEST_SERVER_PORT } from '../test/mockApiServer';
@@ -258,6 +262,49 @@ describe('EppoClient E2E test', () => {
     });
   });
 
+  describe('get precomputed assignments', () => {
+    it('obfuscates assignments', async () => {
+      const client = await init({
+        apiKey,
+        baseUrl: `http://127.0.0.1:${TEST_SERVER_PORT}`,
+        assignmentLogger: mockLogger,
+      });
+      const subjectAttributes = { id: 'zach' };
+      const expectedAssignment = client.getStringAssignment(
+        'new-user-onboarding',
+        'subject',
+        subjectAttributes,
+        'default-value',
+      );
+      expect(expectedAssignment).toBe('purple');
+      const salt = base64.fromUint8Array(new Uint8Array([7, 53, 17, 78]));
+      const encodedPrecomputedWire = client.getPrecomputedConfiguration(
+        'subject',
+        subjectAttributes,
+        {},
+        salt,
+      );
+      const { precomputed } = JSON.parse(encodedPrecomputedWire) as IConfigurationWire;
+      if (!precomputed) {
+        fail('Precomputed data not in Configuration response');
+      }
+      const precomputedResponse = JSON.parse(precomputed.response);
+      expect(precomputedResponse).toBeTruthy();
+      expect(precomputedResponse.salt).toEqual('BzURTg==');
+      const precomputedFlags = precomputedResponse?.flags ?? {};
+      expect(Object.keys(precomputedFlags)).toContain('f0da9e751eb86ad80968df152390fa4f'); // 'new-user-onboarding', md5 hashed
+      const decodedFirstFlag = decodePrecomputedFlag(
+        precomputedFlags['f0da9e751eb86ad80968df152390fa4f'],
+      );
+      expect(decodedFirstFlag.flagKey).toEqual('f0da9e751eb86ad80968df152390fa4f');
+      expect(decodedFirstFlag.variationType).toEqual(VariationType.STRING);
+      expect(decodedFirstFlag.variationKey).toEqual('purple');
+      expect(decodedFirstFlag.variationValue).toEqual('purple');
+      expect(decodedFirstFlag.doLog).toEqual(false);
+      expect(decodedFirstFlag.extraLogging).toEqual({});
+    });
+  });
+
   describe('Shared Bandit Test Cases', () => {
     beforeAll(async () => {
       const dummyBanditLogger: IBanditLogger = {
@@ -367,6 +414,7 @@ describe('EppoClient E2E test', () => {
         client.useExpiringInMemoryBanditAssignmentCache(2);
 
         // Let's say someone is rage refreshing - we want to log assignment only once
+        // eslint-disable-next-line @typescript-eslint/no-unused-vars
         for (const _ of Array(3).keys()) {
           client.getBanditAction(flagKey, bobKey, bobAttributes, bobActions, 'default');
         }

src/index.ts

@@ -1,16 +1,20 @@
 import {
+  Attributes,
+  ContextAttributes,
   EppoClient,
   Flag,
   FlagConfigurationRequestParameters,
   MemoryOnlyConfigurationStore,
   newDefaultEventDispatcher,
 } from '@eppo/js-client-sdk-common';
 import { BanditParameters, BanditVariation } from '@eppo/js-client-sdk-common/dist/interfaces';
-import { Event } from '@eppo/js-client-sdk-common/src/events/event-dispatcher';
+import { BanditActions, FlagKey } from '@eppo/js-client-sdk-common/dist/types';
+import Event from '@eppo/js-client-sdk-common/src/events/event';
 
 import FileBackedNamedEventQueue from './events/file-backed-named-event-queue';
 import { IClientConfig } from './i-client-config';
 import { sdkName, sdkVersion } from './sdk-data';
+import { generateSalt } from './util';
 
 export {
   IAssignmentDetails,
@@ -87,6 +91,23 @@ export async function init(config: IClientConfig): Promise<EppoClient> {
   // Fetch configurations (which will also start regular polling per requestConfiguration)
   await clientInstance.fetchFlagConfigurations();
 
+  // Monkey patch the function to use a generated salt if none is provided
+  const originalGetPrecomputedConfiguration = clientInstance.getPrecomputedConfiguration;
+  clientInstance.getPrecomputedConfiguration = (
+    subjectKey: string,
+    subjectAttributes: Attributes | ContextAttributes = {},
+    banditActions: Record<FlagKey, BanditActions> = {},
+    salt?: string,
+  ) => {
+    return originalGetPrecomputedConfiguration.call(
+      clientInstance,
+      subjectKey,
+      subjectAttributes,
+      banditActions,
+      salt ?? generateSalt(),
+    );
+  };
+
   return clientInstance;
 }
 

src/util.ts

@@ -1,3 +1,7 @@
+import { randomBytes } from 'crypto';
+
+import * as base64 from 'js-base64';
+
 /* Returns elements from arr until the predicate returns false. */
 export function takeWhile<T>(arr: T[], predicate: (item: T) => boolean): T[] {
   const result = [];
@@ -9,3 +13,8 @@ export function takeWhile<T>(arr: T[], predicate: (item: T) => boolean): T[] {
   }
   return result;
 }
+
+export function generateSalt(length = 16): string {
+  const getRandomValues = (length: number) => new Uint8Array(randomBytes(length));
+  return base64.fromUint8Array(getRandomValues(length));
+}

test/testHelpers.ts

@@ -1,7 +1,6 @@
 import * as fs from 'fs';
 
-import { VariationType, AttributeType } from '@eppo/js-client-sdk-common';
-import { ContextAttributes } from '@eppo/js-client-sdk-common/dist/types';
+import { VariationType, AttributeType, ContextAttributes } from '@eppo/js-client-sdk-common';
 
 export const TEST_DATA_DIR = './test/data/ufc/';
 export const ASSIGNMENT_TEST_DATA_DIR = TEST_DATA_DIR + 'tests/';

yarn.lock

@@ -460,10 +460,10 @@
   resolved "https://registry.npmjs.org/@bcoe/v8-coverage/-/v8-coverage-0.2.3.tgz"
   integrity sha512-0hYQ8SB4Db5zvZB4axdMHGwEaQjkZzFjQiN9LVYvIFB2nSUHW9tYpxWriPrWDASIxiaXax83REcLxuSdnGPZtw==
 
-"@eppo/js-client-sdk-common@^4.6.3":
-  version "4.6.3"
-  resolved "https://registry.yarnpkg.com/@eppo/js-client-sdk-common/-/js-client-sdk-common-4.6.3.tgz#89267a1c247bc04725b7701cdfb573613c133ddc"
-  integrity sha512-e2nSvzONjqUiAYUjBMIIk1jWuKPOmBl5AlbiNjsoJAd6dZKN1RWpTmy83hNk6ff/syjAEWTcplls2cU37VbyiQ==
+"@eppo/js-client-sdk-common@4.8.0-alpha.1":
+  version "4.8.0-alpha.1"
+  resolved "https://registry.yarnpkg.com/@eppo/js-client-sdk-common/-/js-client-sdk-common-4.8.0-alpha.1.tgz#3c5c5f9fad5aa4ba582f0f9ea09b5ee60456e4cf"
+  integrity sha512-sB/3D/aj4TvTw44mxb2hWNGB22FrJzvHrQxQ6eGGeTBZkrBJz4wnl3WcvVjiiNPKBJpKxYGs5C0kM/++IHfH6A==
   dependencies:
     buffer "npm:@eppo/[email protected]"
     js-base64 "^3.7.7"