Instrument transformer.go with latency metrics.

Kubernetes-commit: e54864f53de75cd56c0fe94777e1d3de0c559c7f

pkg/storage/value/metrics.go

@@ -0,0 +1,55 @@
+/*
+Copyright 2017 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 value
+
+import (
+	"sync"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+const (
+	valueSubsystem = "value"
+)
+
+var (
+	TransformerOperationalLatencies = prometheus.NewSummaryVec(
+		prometheus.SummaryOpts{
+			Subsystem: valueSubsystem,
+			Name:      "storage_transformation_latency_microseconds",
+			Help:      "Latency in microseconds of value transformation operations.",
+		},
+		[]string{"transformation_type"},
+	)
+)
+
+var registerMetrics sync.Once
+
+func RegisterMetrics() {
+	registerMetrics.Do(func() {
+		prometheus.MustRegister(TransformerOperationalLatencies)
+	})
+}
+
+func RecordTransformation(transformationType string, start time.Time) {
+	TransformerOperationalLatencies.WithLabelValues(transformationType).Observe(sinceInMicroseconds(start))
+}
+
+func sinceInMicroseconds(start time.Time) float64 {
+	return float64(time.Since(start).Nanoseconds() / time.Microsecond.Nanoseconds())
+}

pkg/storage/value/transformer.go

@@ -21,8 +21,13 @@ import (
 	"bytes"
 	"fmt"
 	"sync"
+	"time"
 )
 
+func init() {
+	RegisterMetrics()
+}
+
 // Context is additional information that a storage transformation may need to verify the data at rest.
 type Context interface {
 	// AuthenticatedData should return an array of bytes that describes the current value. If the value changes,
@@ -80,12 +85,14 @@ func (t *MutableTransformer) Set(transformer Transformer) {
 }
 
 func (t *MutableTransformer) TransformFromStorage(data []byte, context Context) (out []byte, stale bool, err error) {
+	defer RecordTransformation("from_storage", time.Now())
 	t.lock.RLock()
 	transformer := t.transformer
 	t.lock.RUnlock()
 	return transformer.TransformFromStorage(data, context)
 }
 func (t *MutableTransformer) TransformToStorage(data []byte, context Context) (out []byte, err error) {
+	defer RecordTransformation("to_storage", time.Now())
 	t.lock.RLock()
 	transformer := t.transformer
 	t.lock.RUnlock()