Merge pull request #77 from statsig-io/fix-user-bucket-condition

Fix user bucket condition

Author: jkw-statsig

package-lock.json

@@ -1,6 +1,6 @@
 {
   "name": "statsig-node",
-  "version": "4.0.1",
+  "version": "4.1.0",
   "description": "Statsig Node.js SDK for usage in multi-user server environments.",
   "main": "src/index.js",
   "scripts": {

package.json

@@ -11,6 +11,8 @@ const SpecStore = require('./SpecStore');
 const UAParser = require('ua-parser-js');
 
 const TYPE_DYNAMIC_CONFIG = 'dynamic_config';
+const CONDITION_SEGMENT_COUNT = 10 * 1000;
+const USER_BUCKET_COUNT = 1000;
 
 const Evaluator = {
   async init(options, secretKey) {
@@ -74,10 +76,12 @@ const Evaluator = {
   },
 
   _evalPassPercent(user, rule, salt) {
-    const bucket = computeUserHashBucket(
+    const hash = computeUserHash(
       salt + '.' + rule.name + '.' + user?.userID ?? '',
     );
-    return bucket < rule.passPercentage * 100;
+    return (
+      Number(hash % BigInt(CONDITION_SEGMENT_COUNT)) < rule.passPercentage * 100
+    );
   },
 
   /**
@@ -141,7 +145,8 @@ const Evaluator = {
         break;
       case 'user_bucket':
         const salt = condition.additionalValues?.salt;
-        value = computeUserHashBucket(salt + '.' + user?.userID ?? '');
+        const userHash = computeUserHash(salt + '.' + user?.userID ?? '');
+        value = Number(userHash % BigInt(USER_BUCKET_COUNT));
         break;
       default:
         return FETCH_FROM_SERVER;
@@ -276,13 +281,12 @@ const Evaluator = {
   },
 };
 
-function computeUserHashBucket(userHash) {
-  const hash = crypto
+function computeUserHash(userHash) {
+  return crypto
     .createHash('sha256')
     .update(userHash)
     .digest()
     .readBigUInt64BE();
-  return Number(hash % BigInt(10000));
 }
 
 function getFromUser(user, field) {

src/Evaluator.js

@@ -189,10 +189,14 @@ describe('Test condition evaluation', () => {
     ['current_time',       'on',             Date.now() - 24 * 3600 * 1000, null,              user, false],
 
     // user bucket
-    ['user_bucket',        'lt',              1000,            null,              { userID: 1},  false, { salt:'himalayan salt' }],
-    ['user_bucket',        'lt',              1000,            null,              { userID: 18}, true,  { salt:'himalayan salt' }],
-    ['user_bucket',        'gt',              8800,            null,              { userID: 1},  true, { salt:'himalayan salt' }],
-    ['user_bucket',        'gt',              8800,            null,              { userID: 18}, false,  { salt:'himalayan salt' }],
+    ['user_bucket',        'lt',              981,            null,              { userID: 1},  true, { salt:'himalayan salt' }],
+    ['user_bucket',        'lt',              229,            null,              { userID: 18}, true,  { salt:'himalayan salt' }],
+    ['user_bucket',        'gt',              980,            null,              { userID: 1},  false, { salt:'himalayan salt' }],
+    ['user_bucket',        'gt',              229,            null,              { userID: 18}, false,  { salt:'himalayan salt' }],
+    ['user_bucket',        'any',             [228, 333, 555],null,              { userID: 18}, true,  { salt:'himalayan salt' }],
+    ['user_bucket',        'any',             [229, 333, 555],null,              { userID: 18}, false,  { salt:'himalayan salt' }],
+    ['user_bucket',        'none',            [229, 333, 555],null,              { userID: 18}, true,  { salt:'himalayan salt' }],
+    // ['user_bucket',        '',                []]
 
     // some random type not implemented yet
     ['derived_field',      'eq',              '0.25',          'd1_retention',     user, FETCH_FROM_SERVER],