feat!: fractional bucketing improvements (#1501)

Signed-off-by: Lea Konvalinka <lea.konvalinka@dynatrace.com>
Signed-off-by: Todd Baert <todd.baert@dynatrace.com>
Co-authored-by: Todd Baert <todd.baert@dynatrace.com>

Author: leakonvalinka

libs/providers/flagd-web/schemas

@@ -24,7 +24,8 @@ describe('in-process', () => {
     loadFeatures(GHERKIN_FLAGD, {
       // remove filters as we add support for features
       // see: https://github.com/open-feature/js-sdk-contrib/issues/1096 and child issues
-      tagFilter: '@in-process and not @targetURI and not @sync and not @unixsocket and not @deprecated',
+      tagFilter:
+        '@in-process and not @targetURI and not @sync and not @unixsocket and not @deprecated and not @fractional-v1 and not @operator-errors',
       scenarioNameTemplate: (vars) => {
         return `${vars.scenarioTitle} (${vars.scenarioTags.join(',')} ${vars.featureTags.join(',')})`;
       },

libs/providers/flagd/schemas

@@ -25,7 +25,7 @@ describe('rpc', () => {
       tagFilter:
         // remove filters as we add support for features
         // see: https://github.com/open-feature/js-sdk-contrib/issues/1096 and child issues
-        '@rpc and not @targetURI and not @caching and not @unixsocket and not @deprecated',
+        '@rpc and not @targetURI and not @caching and not @unixsocket and not @deprecated and not @fractional-v1 and not @operator-errors',
       scenarioNameTemplate: (vars) => {
         return `${vars.scenarioTitle} (${vars.scenarioTags.join(',')} ${vars.featureTags.join(',')})`;
       },

libs/providers/flagd/src/e2e/tests/in-process.spec.ts

@@ -5,15 +5,17 @@ import type { EvaluationContextWithLogger } from './common';
 
 export const fractionalRule = 'fractional';
 
-export function fractional(data: unknown, context: EvaluationContextWithLogger): string | null {
+type VariantValue = string | number | boolean | null;
+
+export function fractional(data: unknown, context: EvaluationContextWithLogger): VariantValue {
   const logger = getLoggerFromContext(context);
   if (!Array.isArray(data)) {
     return null;
   }
 
   const args = Array.from(data);
-  if (args.length < 2) {
-    logger.debug(`Invalid ${fractionalRule} configuration: Expected at least 2 buckets, got ${args.length}`);
+  if (args.length < 1) {
+    logger.debug(`Invalid ${fractionalRule} configuration: Expected at least 1 bucket, got ${args.length}`);
     return null;
   }
 
@@ -48,37 +50,36 @@ export function fractional(data: unknown, context: EvaluationContextWithLogger):
     return null;
   }
 
-  // hash in signed 32 format. Bitwise operation here works in signed 32 hence the conversion
-  const hash = new MurmurHash3(bucketBy).result() | 0;
-  const bucket = (Math.abs(hash) / 2147483648) * 100;
+  const MAX_WEIGHT = 2147483647;
+  if (bucketingList.totalWeight > MAX_WEIGHT) {
+    logger.debug(
+      `Invalid ${fractionalRule} configuration: sum of weights exceeds Math.MaxInt32 (${MAX_WEIGHT}), got ${bucketingList.totalWeight}`,
+    );
+    return null;
+  }
+
+  const hashUint32 = BigInt(new MurmurHash3(bucketBy).result() >>> 0);
+  const bucket = (hashUint32 * BigInt(bucketingList.totalWeight)) >> BigInt(32);
 
-  let sum = 0;
+  let sum = BigInt(0);
   for (let i = 0; i < bucketingList.fractions.length; i++) {
     const bucketEntry = bucketingList.fractions[i];
 
-    sum += relativeWeight(bucketingList.totalWeight, bucketEntry.fraction);
+    sum += BigInt(bucketEntry.fraction);
 
-    if (sum >= bucket) {
+    if (sum > bucket) {
       return bucketEntry.variant;
     }
   }
 
   return null;
 }
 
-function relativeWeight(totalWeight: number, weight: number): number {
-  if (weight == 0) {
-    return 0;
-  }
-  return (weight * 100) / totalWeight;
-}
-
 function toBucketingList(from: unknown[]): {
-  fractions: { variant: string; fraction: number }[];
+  fractions: { variant: VariantValue; fraction: number }[];
   totalWeight: number;
 } {
-  // extract bucketing options
-  const bucketingArray: { variant: string; fraction: number }[] = [];
+  const bucketingArray: { variant: VariantValue; fraction: number }[] = [];
 
   let totalWeight = 0;
   for (let i = 0; i < from.length; i++) {
@@ -91,19 +92,28 @@ function toBucketingList(from: unknown[]): {
       throw new Error('Invalid bucketing entry. Requires at least a variant');
     }
 
-    if (typeof entry[0] !== 'string') {
-      throw new Error('Bucketing require variant to be present in string format');
+    let variant: VariantValue;
+    if (typeof entry[0] === 'string' || typeof entry[0] === 'number' || typeof entry[0] === 'boolean') {
+      variant = entry[0];
+    } else if (entry[0] === null || entry[0] === undefined) {
+      variant = null;
+    } else {
+      throw new Error(
+        'Bucketing requires variant to be a string, number, or boolean (or a JSONLogic expression that evaluates to one)',
+      );
     }
 
     let weight = 1;
     if (entry.length >= 2) {
-      if (typeof entry[1] !== 'number') {
-        throw new Error('Bucketing require bucketing percentage to be present');
+      const raw = entry[1];
+      if (typeof raw !== 'number' || !Number.isInteger(raw)) {
+        throw new Error('Bucketing requires weight to be an integer');
       }
-      weight = entry[1];
+      // negative weights can be the result of rollout calculations, so we clamp to 0 rather than throwing an error
+      weight = Math.max(0, raw);
     }
 
-    bucketingArray.push({ fraction: weight, variant: entry[0] });
+    bucketingArray.push({ fraction: weight, variant });
     totalWeight += weight;
   }