Disambiguate unsupported metrics from metrics errors

pkg/kubelet/server/stats/volume_stat_calculator.go

@@ -98,9 +98,9 @@ func (s *volumeStatCalculator) calcAndStoreStats() {
 		metric, err := v.GetMetrics()
 		if err != nil {
 			// Expected for Volumes that don't support Metrics
-			// TODO: Disambiguate unsupported from errors
-			// See issue #20676
+			if !volume.IsNotSupported(err) {
 				glog.V(4).Infof("Failed to calculate volume metrics for pod %s volume %s: %+v", format.Pod(s.pod), name, err)
+			}
 			continue
 		}
 		stats = append(stats, s.parsePodVolumeStats(name, metric))

pkg/volume/metrics_du.go

@@ -17,9 +17,6 @@ limitations under the License.
 package volume
 
 import (
-	"errors"
-	"fmt"
-
 	"k8s.io/kubernetes/pkg/api/resource"
 	"k8s.io/kubernetes/pkg/volume/util"
 )
@@ -45,7 +42,7 @@ func NewMetricsDu(path string) MetricsProvider {
 func (md *metricsDu) GetMetrics() (*Metrics, error) {
 	metrics := &Metrics{}
 	if md.path == "" {
-		return metrics, errors.New("no path defined for disk usage metrics.")
+		return metrics, NewNoPathDefinedError()
 	}
 
 	err := md.runDu(metrics)
@@ -76,7 +73,7 @@ func (md *metricsDu) runDu(metrics *Metrics) error {
 func (md *metricsDu) getFsInfo(metrics *Metrics) error {
 	available, capacity, _, err := util.FsInfo(md.path)
 	if err != nil {
-		return fmt.Errorf("Failed to get FsInfo due to error %v", err)
+		return NewFsInfoFailedError(err)
 	}
 	metrics.Available = resource.NewQuantity(available, resource.BinarySI)
 	metrics.Capacity = resource.NewQuantity(capacity, resource.BinarySI)

pkg/volume/metrics_errors.go

@@ -0,0 +1,77 @@
+/*
+Copyright 2016 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package volume
+
+import (
+	"fmt"
+)
+
+const (
+	// ErrCodeNotSupported code for NotSupported Errors.
+	ErrCodeNotSupported int = iota + 1
+	ErrCodeNoPathDefined
+	ErrCodeFsInfoFailed
+)
+
+// NewNotSupportedError creates a new MetricsError with code NotSupported.
+func NewNotSupportedError() *MetricsError {
+	return &MetricsError{
+		Code: ErrCodeNotSupported,
+		Msg:  "metrics are not supported for MetricsNil Volumes",
+	}
+}
+
+// NewNoPathDefined creates a new MetricsError with code NoPathDefined.
+func NewNoPathDefinedError() *MetricsError {
+	return &MetricsError{
+		Code: ErrCodeNoPathDefined,
+		Msg:  "no path defined for disk usage metrics.",
+	}
+}
+
+// NewFsInfoFailedError creates a new MetricsError with code FsInfoFailed.
+func NewFsInfoFailedError(err error) *MetricsError {
+	return &MetricsError{
+		Code: ErrCodeFsInfoFailed,
+		Msg:  fmt.Sprintf("Failed to get FsInfo due to error %v", err),
+	}
+}
+
+// MetricsError to distinguish different Metrics Errors.
+type MetricsError struct {
+	Code int
+	Msg  string
+}
+
+func (e *MetricsError) Error() string {
+	return fmt.Sprintf("%s", e.Msg)
+}
+
+// IsNotSupported returns true if and only if err is "key" not found error.
+func IsNotSupported(err error) bool {
+	return isErrCode(err, ErrCodeNotSupported)
+}
+
+func isErrCode(err error, code int) bool {
+	if err == nil {
+		return false
+	}
+	if e, ok := err.(*MetricsError); ok {
+		return e.Code == code
+	}
+	return false
+}

pkg/volume/metrics_nil.go

@@ -16,8 +16,6 @@ limitations under the License.
 
 package volume
 
-import "errors"
-
 var _ MetricsProvider = &MetricsNil{}
 
 // MetricsNil represents a MetricsProvider that does not support returning
@@ -28,5 +26,5 @@ type MetricsNil struct{}
 // GetMetrics returns an empty Metrics and an error.
 // See MetricsProvider.GetMetrics
 func (*MetricsNil) GetMetrics() (*Metrics, error) {
-	return &Metrics{}, errors.New("metrics are not supported for MetricsNil Volumes")
+	return &Metrics{}, NewNotSupportedError()
 }

pkg/volume/metrics_statfs.go

@@ -17,9 +17,6 @@ limitations under the License.
 package volume
 
 import (
-	"errors"
-	"fmt"
-
 	"k8s.io/kubernetes/pkg/api/resource"
 	"k8s.io/kubernetes/pkg/volume/util"
 )
@@ -44,7 +41,7 @@ func NewMetricsStatFS(path string) MetricsProvider {
 func (md *metricsStatFS) GetMetrics() (*Metrics, error) {
 	metrics := &Metrics{}
 	if md.path == "" {
-		return metrics, errors.New("no path defined for disk usage metrics.")
+		return metrics, NewNoPathDefinedError()
 	}
 
 	err := md.getFsInfo(metrics)
@@ -59,7 +56,7 @@ func (md *metricsStatFS) GetMetrics() (*Metrics, error) {
 func (md *metricsStatFS) getFsInfo(metrics *Metrics) error {
 	available, capacity, usage, err := util.FsInfo(md.path)
 	if err != nil {
-		return fmt.Errorf("Failed to get FsInfo due to error %v", err)
+		return NewFsInfoFailedError(err)
 	}
 	metrics.Available = resource.NewQuantity(available, resource.BinarySI)
 	metrics.Capacity = resource.NewQuantity(capacity, resource.BinarySI)