1 files changed, 134 insertions, 0 deletions
diff --git a/weed/worker/tasks/balance/detection.go b/weed/worker/tasks/balance/detection.go
new file mode 100644
index 000000000..f4bcf3ca3
--- /dev/null
+++ b/weed/worker/tasks/balance/detection.go
@@ -0,0 +1,134 @@
+package balance
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/seaweedfs/seaweedfs/weed/glog"
+	"github.com/seaweedfs/seaweedfs/weed/worker/tasks/base"
+	"github.com/seaweedfs/seaweedfs/weed/worker/types"
+)
+
+// Detection implements the detection logic for balance tasks
+func Detection(metrics []*types.VolumeHealthMetrics, clusterInfo *types.ClusterInfo, config base.TaskConfig) ([]*types.TaskDetectionResult, error) {
+	if !config.IsEnabled() {
+		return nil, nil
+	}
+
+	balanceConfig := config.(*Config)
+
+	// Skip if cluster is too small
+	minVolumeCount := 2 // More reasonable for small clusters
+	if len(metrics) < minVolumeCount {
+		glog.Infof("BALANCE: No tasks created - cluster too small (%d volumes, need ≥%d)", len(metrics), minVolumeCount)
+		return nil, nil
+	}
+
+	// Analyze volume distribution across servers
+	serverVolumeCounts := make(map[string]int)
+	for _, metric := range metrics {
+		serverVolumeCounts[metric.Server]++
+	}
+
+	if len(serverVolumeCounts) < balanceConfig.MinServerCount {
+		glog.Infof("BALANCE: No tasks created - too few servers (%d servers, need ≥%d)", len(serverVolumeCounts), balanceConfig.MinServerCount)
+		return nil, nil
+	}
+
+	// Calculate balance metrics
+	totalVolumes := len(metrics)
+	avgVolumesPerServer := float64(totalVolumes) / float64(len(serverVolumeCounts))
+
+	maxVolumes := 0
+	minVolumes := totalVolumes
+	maxServer := ""
+	minServer := ""
+
+	for server, count := range serverVolumeCounts {
+		if count > maxVolumes {
+			maxVolumes = count
+			maxServer = server
+		}
+		if count < minVolumes {
+			minVolumes = count
+			minServer = server
+		}
+	}
+
+	// Check if imbalance exceeds threshold
+	imbalanceRatio := float64(maxVolumes-minVolumes) / avgVolumesPerServer
+	if imbalanceRatio <= balanceConfig.ImbalanceThreshold {
+		glog.Infof("BALANCE: No tasks created - cluster well balanced. Imbalance=%.1f%% (threshold=%.1f%%). Max=%d volumes on %s, Min=%d on %s, Avg=%.1f",
+			imbalanceRatio*100, balanceConfig.ImbalanceThreshold*100, maxVolumes, maxServer, minVolumes, minServer, avgVolumesPerServer)
+		return nil, nil
+	}
+
+	// Select a volume from the overloaded server for balance
+	var selectedVolume *types.VolumeHealthMetrics
+	for _, metric := range metrics {
+		if metric.Server == maxServer {
+			selectedVolume = metric
+			break
+		}
+	}
+
+	if selectedVolume == nil {
+		glog.Warningf("BALANCE: Could not find volume on overloaded server %s", maxServer)
+		return nil, nil
+	}
+
+	// Create balance task with volume and destination planning info
+	reason := fmt.Sprintf("Cluster imbalance detected: %.1f%% (max: %d on %s, min: %d on %s, avg: %.1f)",
+		imbalanceRatio*100, maxVolumes, maxServer, minVolumes, minServer, avgVolumesPerServer)
+
+	task := &types.TaskDetectionResult{
+		TaskType:   types.TaskTypeBalance,
+		VolumeID:   selectedVolume.VolumeID,
+		Server:     selectedVolume.Server,
+		Collection: selectedVolume.Collection,
+		Priority:   types.TaskPriorityNormal,
+		Reason:     reason,
+		ScheduleAt: time.Now(),
+		// TypedParams will be populated by the maintenance integration
+		// with destination planning information
+	}
+
+	return []*types.TaskDetectionResult{task}, nil
+}
+
+// Scheduling implements the scheduling logic for balance tasks
+func Scheduling(task *types.Task, runningTasks []*types.Task, availableWorkers []*types.Worker, config base.TaskConfig) bool {
+	balanceConfig := config.(*Config)
+
+	// Count running balance tasks
+	runningBalanceCount := 0
+	for _, runningTask := range runningTasks {
+		if runningTask.Type == types.TaskTypeBalance {
+			runningBalanceCount++
+		}
+	}
+
+	// Check concurrency limit
+	if runningBalanceCount >= balanceConfig.MaxConcurrent {
+		return false
+	}
+
+	// Check if we have available workers
+	availableWorkerCount := 0
+	for _, worker := range availableWorkers {
+		for _, capability := range worker.Capabilities {
+			if capability == types.TaskTypeBalance {
+				availableWorkerCount++
+				break
+			}
+		}
+	}
+
+	return availableWorkerCount > 0
+}
+
+// CreateTask creates a new balance task instance
+func CreateTask(params types.TaskParams) (types.TaskInterface, error) {
+	// Create and return the balance task using existing Task type
+	return NewTask(params.Server, params.VolumeID, params.Collection), nil
+}