feat: [FFM-12306]: Enhance caching key (#153)

* apply security audit fix

* feat: [FFM-12306]: Add config to allow target attributes to be used when creating cache key

README.md

@@ -314,6 +314,14 @@ interface CacheOptions {
   // storage mechanism to use, conforming to the Web Storage API standard, can be either synchronous or asynchronous
   // defaults to localStorage
   storage?: AsyncStorage | SyncStorage
+  /**
+   * use target attributes when deriving the cache key
+   * when set to `false` or omitted, the key will be formed using only the target identifier and SDK key
+   * when set to `true`, all target attributes with be used in addition to the target identifier and SDK key
+   * can be set to an array of target attributes to use a subset in addition to the target identifier and SDK key
+   * defaults to false
+   */
+  deriveKeyFromTargetAttributes?: boolean | string[]
 }
 ```
 
@@ -355,7 +363,7 @@ If the request is aborted due to this timeout the SDK will fail to initialize an
 
 The default value if not specified is `0` which means that no timeout will occur.
 
-**This only applies to the authentiaction request. If you wish to set a read timeout on the remaining requests made by the SDK, you may register [API Middleware](#api-middleware)
+**This only applies to the authentication request. If you wish to set a read timeout on the remaining requests made by the SDK, you may register [API Middleware](#api-middleware)
 
 ```typescript
 const options = {

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@harnessio/ff-javascript-client-sdk",
-  "version": "1.29.0",
+  "version": "1.30.0",
   "author": "Harness",
   "license": "Apache-2.0",
   "main": "dist/sdk.cjs.js",

src/__tests__/cache.test.ts

@@ -1,5 +1,5 @@
-import type { AsyncStorage, Evaluation, SyncStorage } from '../types'
-import { getCache } from '../cache'
+import type { AsyncStorage, Evaluation, SyncStorage, Target } from '../types'
+import { createCacheIdSeed, getCache } from '../cache'
 
 const sampleEvaluations: Evaluation[] = [
   { flag: 'flag1', value: 'false', kind: 'boolean', identifier: 'false' },
@@ -149,3 +149,38 @@ describe('getCache', () => {
     })
   })
 })
+
+describe('createCacheIdSeed', () => {
+  const apiKey = 'abc123'
+  const target: Target = {
+    name: 'Test Name',
+    identifier: 'test-identifier',
+    attributes: {
+      a: 'bcd',
+      b: 123,
+      c: ['x', 'y', 'z']
+    }
+  }
+
+  test('it should return the target id and api key when deriveKeyFromTargetAttributes is omitted', async () => {
+    expect(createCacheIdSeed(target, apiKey)).toEqual(target.identifier + apiKey)
+  })
+
+  test('it should return the target id and api key when deriveKeyFromTargetAttributes is false', async () => {
+    expect(createCacheIdSeed(target, apiKey, { deriveKeyFromTargetAttributes: false })).toEqual(
+      target.identifier + apiKey
+    )
+  })
+
+  test('it should return the target id and api key with all attributes when deriveKeyFromTargetAttributes is true', async () => {
+    expect(createCacheIdSeed(target, apiKey, { deriveKeyFromTargetAttributes: true })).toEqual(
+      '{"a":"bcd","b":123,"c":["x","y","z"]}test-identifierabc123'
+    )
+  })
+
+  test('it should return the target id and api key with a subset of attributes when deriveKeyFromTargetAttributes is an array', async () => {
+    expect(createCacheIdSeed(target, apiKey, { deriveKeyFromTargetAttributes: ['a', 'c'] })).toEqual(
+      '{"a":"bcd","c":["x","y","z"]}test-identifierabc123'
+    )
+  })
+})

src/cache.ts

@@ -1,4 +1,5 @@
-import type { AsyncStorage, CacheOptions, Evaluation, SyncStorage } from './types'
+import type { AsyncStorage, CacheOptions, Evaluation, SyncStorage, Target } from './types'
+import { sortEvaluations } from './utils'
 
 export interface GetCacheResponse {
   loadFromCache: () => Promise<Evaluation[]>
@@ -48,7 +49,7 @@ async function clearCachedEvaluations(cacheId: string, storage: AsyncStorage): P
 }
 
 async function saveToCache(cacheId: string, storage: AsyncStorage, evaluations: Evaluation[]): Promise<void> {
-  await storage.setItem(cacheId, JSON.stringify(evaluations))
+  await storage.setItem(cacheId, JSON.stringify(sortEvaluations(evaluations)))
   await storage.setItem(cacheId + '.ts', Date.now().toString())
 }
 
@@ -76,6 +77,28 @@ async function removeCachedEvaluation(cacheId: string, storage: AsyncStorage, fl
   }
 }
 
+export function createCacheIdSeed(target: Target, apiKey: string, config: CacheOptions = {}) {
+  if (!config.deriveKeyFromTargetAttributes) return target.identifier + apiKey
+
+  return (
+    JSON.stringify(
+      Object.keys(target.attributes || {})
+        .sort()
+        .filter(
+          attribute =>
+            !Array.isArray(config.deriveKeyFromTargetAttributes) ||
+            config.deriveKeyFromTargetAttributes.includes(attribute)
+        )
+        .reduce(
+          (filteredAttributes, attribute) => ({ ...filteredAttributes, [attribute]: target.attributes[attribute] }),
+          {}
+        )
+    ) +
+    target.identifier +
+    apiKey
+  )
+}
+
 async function getCacheId(seed: string): Promise<string> {
   let cacheId = seed
 

src/index.ts

@@ -16,12 +16,12 @@ import type {
   DefaultVariationEventPayload
 } from './types'
 import { Event } from './types'
-import { defer, encodeTarget, getConfiguration } from './utils'
+import { defer, encodeTarget, getConfiguration, sortEvaluations } from './utils'
 import { addMiddlewareToFetch } from './request'
 import { Streamer } from './stream'
 import { getVariation } from './variation'
 import Poller from './poller'
-import { getCache } from './cache'
+import { createCacheIdSeed, getCache } from './cache'
 
 const SDK_VERSION = '1.26.1'
 const SDK_INFO = `Javascript ${SDK_VERSION} Client`
@@ -110,10 +110,9 @@ const initialize = (apiKey: string, target: Target, options?: Options): Result =
       try {
         let initialLoad = true
 
-        const cache = await getCache(
-          target.identifier + apiKey,
-          typeof configurations.cache === 'boolean' ? {} : configurations.cache
-        )
+        const cacheConfig = typeof configurations.cache === 'boolean' ? {} : configurations.cache
+
+        const cache = await getCache(createCacheIdSeed(target, apiKey, cacheConfig), cacheConfig)
 
         const cachedEvaluations = await cache.loadFromCache()
 
@@ -441,7 +440,7 @@ const initialize = (apiKey: string, target: Target, options?: Options): Result =
       )
 
       if (res.ok) {
-        const data = await res.json()
+        const data = sortEvaluations(await res.json())
         data.forEach(registerEvaluation)
         eventBus.emit(Event.FLAGS_LOADED, data)
         return { type: 'success', data: data }

src/types.ts

@@ -196,6 +196,14 @@ export interface CacheOptions {
    * @default localStorage
    */
   storage?: AsyncStorage | SyncStorage
+  /**
+   * Use target attributes when deriving the cache key
+   * When set to `false` or omitted, the key will be formed using only the target identifier and SDK key
+   * When set to `true`, all target attributes with be used in addition to the target identifier and SDK key
+   * Can be set to an array of target attributes to use a subset in addition to the target identifier and SDK key
+   * @default false
+   */
+  deriveKeyFromTargetAttributes?: boolean | string[]
 }
 
 export interface Logger {

src/utils.ts

@@ -1,4 +1,4 @@
-import type { Options, Target } from './types'
+import type { Evaluation, Options, Target } from './types'
 
 export const MIN_EVENTS_SYNC_INTERVAL = 60000
 export const MIN_POLLING_INTERVAL = 60000
@@ -99,3 +99,7 @@ const utf8encode = (str: string): string =>
       )
     })
     .join('')
+
+export function sortEvaluations(evaluations: Evaluation[]): Evaluation[] {
+  return [...evaluations].sort(({ flag: flagA }, { flag: flagB }) => (flagA < flagB ? -1 : 1))
+}