add scheduling diagnosis

Signed-off-by: Garrybest <garrybest@foxmail.com>

pkg/scheduler/core/generic_scheduler.go

@@ -58,12 +58,16 @@ func (g *genericScheduler) Schedule(ctx context.Context, placement *policyv1alph
 		return result, fmt.Errorf("no clusters available to schedule")
 	}
 
-	feasibleClusters, err := g.findClustersThatFit(ctx, g.scheduleFramework, placement, spec, clusterInfoSnapshot)
+	feasibleClusters, diagnosis, err := g.findClustersThatFit(ctx, g.scheduleFramework, placement, spec, clusterInfoSnapshot)
 	if err != nil {
 		return result, fmt.Errorf("failed to findClustersThatFit: %v", err)
 	}
+
 	if len(feasibleClusters) == 0 {
-		return result, fmt.Errorf("no clusters fit")
+		return result, &framework.FitError{
+			NumAllClusters: clusterInfoSnapshot.NumOfClusters(),
+			Diagnosis:      diagnosis,
+		}
 	}
 	klog.V(4).Infof("feasible clusters found: %v", feasibleClusters)
 
@@ -97,21 +101,27 @@ func (g *genericScheduler) findClustersThatFit(
 	fwk framework.Framework,
 	placement *policyv1alpha1.Placement,
 	bindingSpec *workv1alpha2.ResourceBindingSpec,
-	clusterInfo *cache.Snapshot) ([]*clusterv1alpha1.Cluster, error) {
+	clusterInfo *cache.Snapshot,
+) ([]*clusterv1alpha1.Cluster, framework.Diagnosis, error) {
 	defer metrics.ScheduleStep(metrics.ScheduleStepFilter, time.Now())
 
+	diagnosis := framework.Diagnosis{
+		ClusterToResultMap: make(framework.ClusterToResultMap),
+	}
+
 	var out []*clusterv1alpha1.Cluster
 	// DO NOT filter unhealthy cluster, let users make decisions by using ClusterTolerations of Placement.
 	clusters := clusterInfo.GetClusters()
 	for _, c := range clusters {
 		if result := fwk.RunFilterPlugins(ctx, placement, bindingSpec, c.Cluster()); !result.IsSuccess() {
 			klog.V(4).Infof("cluster %q is not fit, reason: %v", c.Cluster().Name, result.AsError())
+			diagnosis.ClusterToResultMap[c.Cluster().Name] = result
 		} else {
 			out = append(out, c.Cluster())
 		}
 	}
 
-	return out, nil
+	return out, diagnosis, nil
 }
 
 // prioritizeClusters prioritize the clusters by running the score plugins.

pkg/scheduler/framework/interface.go

@@ -126,6 +126,11 @@ func (s *Result) AsError() error {
 	return errors.New(strings.Join(s.reasons, ", "))
 }
 
+// Reasons returns reasons of the Result.
+func (s *Result) Reasons() []string {
+	return s.reasons
+}
+
 // ScorePlugin is an interface that must be implemented by "Score" plugins to rank
 // clusters that passed the filtering phase.
 type ScorePlugin interface {

pkg/scheduler/framework/plugins/apienablement/api_enablement.go

@@ -37,7 +37,7 @@ func (p *APIEnablement) Filter(ctx context.Context, placement *policyv1alpha1.Pl
 	bindingSpec *workv1alpha2.ResourceBindingSpec, cluster *clusterv1alpha1.Cluster) *framework.Result {
 	if !helper.IsAPIEnabled(cluster.Status.APIEnablements, bindingSpec.Resource.APIVersion, bindingSpec.Resource.Kind) {
 		klog.V(2).Infof("Cluster(%s) not fit as missing API(%s, kind=%s)", cluster.Name, bindingSpec.Resource.APIVersion, bindingSpec.Resource.Kind)
-		return framework.NewResult(framework.Unschedulable, "no such API resource")
+		return framework.NewResult(framework.Unschedulable, "cluster(s) didn't have the API resource")
 	}
 
 	return framework.NewResult(framework.Success)

pkg/scheduler/framework/plugins/clusteraffinity/cluster_affinity.go

@@ -39,7 +39,7 @@ func (p *ClusterAffinity) Filter(ctx context.Context, placement *policyv1alpha1.
 		if util.ClusterMatches(cluster, *affinity) {
 			return framework.NewResult(framework.Success)
 		}
-		return framework.NewResult(framework.Unschedulable, "cluster is not matched the placement cluster affinity constraint")
+		return framework.NewResult(framework.Unschedulable, "cluster(s) didn't match the placement cluster affinity constraint")
 	}
 
 	// If no clusters specified and it is not excluded, mark it matched

pkg/scheduler/framework/plugins/spreadconstraint/spread_constraint.go

@@ -34,11 +34,11 @@ func (p *SpreadConstraint) Filter(ctx context.Context, placement *policyv1alpha1
 	bindingSpec *workv1alpha2.ResourceBindingSpec, cluster *clusterv1alpha1.Cluster) *framework.Result {
 	for _, spreadConstraint := range placement.SpreadConstraints {
 		if spreadConstraint.SpreadByField == policyv1alpha1.SpreadByFieldProvider && cluster.Spec.Provider == "" {
-			return framework.NewResult(framework.Unschedulable, "No Provider Property in the Cluster.Spec")
+			return framework.NewResult(framework.Unschedulable, "cluster(s) didn't have provider property")
 		} else if spreadConstraint.SpreadByField == policyv1alpha1.SpreadByFieldRegion && cluster.Spec.Region == "" {
-			return framework.NewResult(framework.Unschedulable, "No Region Property in the Cluster.Spec")
+			return framework.NewResult(framework.Unschedulable, "cluster(s) didn't have region property")
 		} else if spreadConstraint.SpreadByField == policyv1alpha1.SpreadByFieldZone && cluster.Spec.Zone == "" {
-			return framework.NewResult(framework.Unschedulable, "No Zone Property in the Cluster.Spec")
+			return framework.NewResult(framework.Unschedulable, "cluster(s) didn't have zone property")
 		}
 	}
 

pkg/scheduler/framework/plugins/tainttoleration/taint_toleration.go

@@ -52,6 +52,5 @@ func (p *TaintToleration) Filter(ctx context.Context, placement *policyv1alpha1.
 		return framework.NewResult(framework.Success)
 	}
 
-	return framework.NewResult(framework.Unschedulable, fmt.Sprintf("cluster had taint {%s: %s}, that the propagation policy didn't tolerate",
-		taint.Key, taint.Value))
+	return framework.NewResult(framework.Unschedulable, fmt.Sprintf("cluster(s) had untolerated taint {%s: %s}", taint.Key, taint.Value))
 }

pkg/scheduler/framework/types.go

@@ -1,9 +1,21 @@
 package framework
 
 import (
+	"fmt"
+	"sort"
+	"strings"
+
 	clusterv1alpha1 "github.com/karmada-io/karmada/pkg/apis/cluster/v1alpha1"
 )
 
+const (
+	// NoClusterAvailableMsg is used to format message when no clusters available.
+	NoClusterAvailableMsg = "0/%v clusters are available"
+)
+
+// ClusterToResultMap declares map from cluster name to its Result.
+type ClusterToResultMap map[string]*Result
+
 // ClusterInfo is cluster level aggregated information.
 type ClusterInfo struct {
 	// Overall cluster information.
@@ -24,3 +36,35 @@ func (n *ClusterInfo) Cluster() *clusterv1alpha1.Cluster {
 	}
 	return n.cluster
 }
+
+// Diagnosis records the details to diagnose a scheduling failure.
+type Diagnosis struct {
+	ClusterToResultMap ClusterToResultMap
+}
+
+// FitError describes a fit error of a object.
+type FitError struct {
+	NumAllClusters int
+	Diagnosis      Diagnosis
+}
+
+// Error returns detailed information of why the object failed to fit on each cluster
+func (f *FitError) Error() string {
+	reasons := make(map[string]int)
+	for _, result := range f.Diagnosis.ClusterToResultMap {
+		for _, reason := range result.Reasons() {
+			reasons[reason]++
+		}
+	}
+
+	sortReasonsHistogram := func() []string {
+		var reasonStrings []string
+		for k, v := range reasons {
+			reasonStrings = append(reasonStrings, fmt.Sprintf("%v %v", v, k))
+		}
+		sort.Strings(reasonStrings)
+		return reasonStrings
+	}
+	reasonMsg := fmt.Sprintf(NoClusterAvailableMsg+": %v.", f.NumAllClusters, strings.Join(sortReasonsHistogram(), ", "))
+	return reasonMsg
+}