Skip to content

fix flake in weighted random picker #1561

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. Weโ€™ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Sep 10, 2025
Merged

fix flake in weighted random picker #1561

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
24 changes: 10 additions & 14 deletions pkg/epp/scheduling/framework/plugins/picker/picker_test.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@ package picker

import (
"context"
"math"
"testing"

"github.com/google/go-cmp/cmp"
Expand Down Expand Up @@ -138,8 +139,8 @@ func TestPickMaxScorePicker(t *testing.T) {

func TestPickWeightedRandomPicker(t *testing.T) {
const (
testIterations = 1000
tolerance = 0.2 // 20% tolerance in [0,1] range
testIterations = 10000
tolerance = 0.05 // Verify within tolerance ยฑ5%
)

pod1 := &types.PodMetrics{Pod: &backend.Pod{NamespacedName: k8stypes.NamespacedName{Name: "pod1"}}}
Expand Down Expand Up @@ -197,14 +198,14 @@ func TestPickWeightedRandomPicker(t *testing.T) {
for _, test := range tests {
t.Run(test.name, func(t *testing.T) {
picker := NewWeightedRandomPicker(test.maxPods)
selectionCounts := make(map[string]int)

// Calculate expected probabilities based on scores
// Summarize the total score of all pods
totalScore := 0.0
for _, pod := range test.input {
totalScore += pod.Score
}

// Calculate expected probabilities based on scores
expectedProbabilities := make(map[string]float64)
for _, pod := range test.input {
podName := pod.GetPod().NamespacedName.Name
Expand All @@ -216,32 +217,27 @@ func TestPickWeightedRandomPicker(t *testing.T) {
}

// Initialize selection counters for each pod
selectionCounts := make(map[string]int)
for _, pod := range test.input {
podName := pod.GetPod().NamespacedName.Name
selectionCounts[podName] = 0
}

// Run multiple iterations to gather statistical data
for i := 0; i < testIterations; i++ {
for range testIterations {
result := picker.Pick(context.Background(), types.NewCycleState(), test.input)

// Count selections for probability analysis
if len(result.TargetPods) > 0 {
selectedPodName := result.TargetPods[0].GetPod().NamespacedName.Name
selectionCounts[selectedPodName]++
}
selectedPodName := result.TargetPods[0].GetPod().NamespacedName.Name
selectionCounts[selectedPodName]++
}

// Verify probability distribution
for podName, expectedProb := range expectedProbabilities {
actualCount := selectionCounts[podName]
actualProb := float64(actualCount) / float64(testIterations)

toleranceValue := expectedProb * tolerance
lowerBound := expectedProb - toleranceValue
upperBound := expectedProb + toleranceValue

if actualProb < lowerBound || actualProb > upperBound {
if math.Abs(actualProb-expectedProb) > tolerance {
t.Errorf("Pod %s: expected probability %.3f ยฑ%.1f%%, got %.3f (count: %d/%d)",
podName, expectedProb, tolerance*100, actualProb, actualCount, testIterations)
} else {
Expand Down