add basic metrics utility functions

relax latency check to be greater than instead of within threshold

pkg/metrics/metrics.go

@@ -0,0 +1,177 @@
+/*
+Copyright 2020 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 metrics
+
+import (
+	"fmt"
+	"net"
+	"net/http"
+	"sync"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"k8s.io/apimachinery/pkg/types"
+	k8smetrics "k8s.io/component-base/metrics"
+	"k8s.io/klog"
+)
+
+const (
+	opStatusUnknown      = "Unknown"
+	labelDriverName      = "driver_name"
+	labelOperationName   = "operation_name"
+	labelOperationStatus = "operation_status"
+	subSystem            = "snapshot_controller"
+	metricName           = "operation_total_seconds"
+	metricHelpMsg        = "Total number of seconds spent by the controller on an operation from end to end"
+)
+
+// OperationStatus is the interface type for representing an operation's execution
+// status, with the nil value representing an "Unknown" status of the operation.
+type OperationStatus interface {
+	String() string
+}
+
+var metricBuckets = []float64{0.1, 0.25, 0.5, 1, 2.5, 5, 10, 15, 30, 60, 120, 300, 600}
+
+type MetricsManager interface {
+	// StartMetricsEndpoint starts the metrics endpoint at the specified addr/pattern for
+	// metrics managed by this MetricsManager. It spawns a goroutine to listen to
+	// and serve HTTP requests received on addr/pattern.
+	// If the "pattern" is empty (i.e., ""), no endpoint will be started.
+	// An error will be returned if there is any.
+	StartMetricsEndpoint(pattern, addr string, logger promhttp.Logger, wg *sync.WaitGroup) (*http.Server, error)
+
+	// OperationStart takes in an operation and caches its start time.
+	// if the operation already exists, it's an no-op.
+	OperationStart(op Operation)
+
+	// DropOperation removes an operation from cache.
+	// if the operation does not exist, it's an no-op.
+	DropOperation(op Operation)
+
+	// RecordMetrics records a metric point. Note that it will be an no-op if an
+	// operation has NOT been marked "Started" previously via invoking "OperationStart".
+	// Invoking of RecordMetrics effectively removes the cached entry.
+	// op - the operation which the metric is associated with.
+	// status - the operation status, if not specified, i.e., status == nil, an
+	//          "Unknown" status of the passed-in operation is assumed.
+	RecordMetrics(op Operation, status OperationStatus)
+}
+
+// Operation is a structure which holds information to identify a snapshot
+// related operation
+type Operation struct {
+	// the name of the operation, for example: "CreateSnapshot", "DeleteSnapshot"
+	Name string
+	// the name of the driver which executes the operation
+	Driver string
+	// the resource UID to which the operation has been executed against
+	ResourceID types.UID
+}
+
+type operationMetricsManager struct {
+	// cache is a concurrent-safe map which stores start timestamps for all
+	// ongoing operations.
+	// key is an Operation
+	// value is the timestamp of the start time of the operation
+	cache sync.Map
+
+	// registry is a wrapper around Prometheus Registry
+	registry k8smetrics.KubeRegistry
+
+	// opLatencyMetrics is a Histogram metrics
+	opLatencyMetrics *k8smetrics.HistogramVec
+}
+
+func NewMetricsManager() MetricsManager {
+	mgr := &operationMetricsManager{
+		cache: sync.Map{},
+	}
+	mgr.init()
+	return mgr
+}
+
+func (opMgr *operationMetricsManager) OperationStart(op Operation) {
+	opMgr.cache.LoadOrStore(op, time.Now())
+}
+
+func (opMgr *operationMetricsManager) DropOperation(op Operation) {
+	opMgr.cache.Delete(op)
+}
+
+func (opMgr *operationMetricsManager) RecordMetrics(op Operation, status OperationStatus) {
+	obj, exists := opMgr.cache.Load(op)
+	if !exists {
+		// the operation has not been cached, return directly
+		return
+	}
+	ts, ok := obj.(time.Time)
+	if !ok {
+		// the cached item is not a time.Time, should NEVER happen, clean and return
+		klog.Errorf("Invalid cache entry for key %v", op)
+		opMgr.cache.Delete(op)
+		return
+	}
+	strStatus := opStatusUnknown
+	if status != nil {
+		strStatus = status.String()
+	}
+	duration := time.Since(ts).Seconds()
+	opMgr.opLatencyMetrics.WithLabelValues(op.Driver, op.Name, strStatus).Observe(duration)
+	opMgr.cache.Delete(op)
+}
+
+func (opMgr *operationMetricsManager) init() {
+	opMgr.registry = k8smetrics.NewKubeRegistry()
+	opMgr.opLatencyMetrics = k8smetrics.NewHistogramVec(
+		&k8smetrics.HistogramOpts{
+			Subsystem: subSystem,
+			Name:      metricName,
+			Help:      metricHelpMsg,
+			Buckets:   metricBuckets,
+		},
+		[]string{labelDriverName, labelOperationName, labelOperationStatus},
+	)
+	opMgr.registry.MustRegister(opMgr.opLatencyMetrics)
+}
+
+func (opMgr *operationMetricsManager) StartMetricsEndpoint(pattern, addr string, logger promhttp.Logger, wg *sync.WaitGroup) (*http.Server, error) {
+	if addr == "" {
+		return nil, fmt.Errorf("metrics endpoint will not be started as endpoint address is not specified")
+	}
+	// start listening
+	l, err := net.Listen("tcp", addr)
+	if err != nil {
+		return nil, fmt.Errorf("failed to listen on address[%s], error[%v]", addr, err)
+	}
+	mux := http.NewServeMux()
+	mux.Handle(pattern, k8smetrics.HandlerFor(
+		opMgr.registry,
+		k8smetrics.HandlerOpts{
+			ErrorLog:      logger,
+			ErrorHandling: k8smetrics.ContinueOnError,
+		}))
+	srv := &http.Server{Addr: l.Addr().String(), Handler: mux}
+	// start serving the endpoint
+	go func() {
+		defer wg.Done()
+		if err := srv.Serve(l); err != http.ErrServerClosed {
+			klog.Fatalf("failed to start endpoint at:%s/%s, error: %v", addr, pattern, err)
+		}
+	}()
+	return srv, nil
+}