Add a metric exposing etcd database size

Kubernetes-commit: 922ec728de9248657f026eb6cfb8fdaeb11049ac

pkg/server/options/etcd.go

@@ -176,6 +176,9 @@ func (s *EtcdOptions) AddFlags(fs *pflag.FlagSet) {
 
 	fs.DurationVar(&s.StorageConfig.CountMetricPollPeriod, "etcd-count-metric-poll-period", s.StorageConfig.CountMetricPollPeriod, ""+
 		"Frequency of polling etcd for number of resources per type. 0 disables the metric collection.")
+
+	fs.DurationVar(&s.StorageConfig.DBMetricPollInterval, "etcd-db-metric-poll-interval", s.StorageConfig.DBMetricPollInterval,
+		"The interval of requests to poll etcd and update metric. 0 disables the metric collection")
 }
 
 func (s *EtcdOptions) ApplyTo(c *server.Config) error {

pkg/storage/etcd3/metrics/metrics.go

@@ -49,6 +49,14 @@ var (
 		},
 		[]string{"resource"},
 	)
+	dbTotalSize = compbasemetrics.NewGaugeVec(
+		&compbasemetrics.GaugeOpts{
+			Name:           "etcd_db_total_size_in_bytes",
+			Help:           "Total size of the etcd database file physically allocated in bytes.",
+			StabilityLevel: compbasemetrics.ALPHA,
+		},
+		[]string{"endpoint"},
+	)
 )
 
 var registerMetrics sync.Once
@@ -59,6 +67,7 @@ func Register() {
 	registerMetrics.Do(func() {
 		legacyregistry.MustRegister(etcdRequestLatency)
 		legacyregistry.MustRegister(objectCounts)
+		legacyregistry.MustRegister(dbTotalSize)
 	})
 }
 
@@ -81,3 +90,8 @@ func Reset() {
 func sinceInSeconds(start time.Time) float64 {
 	return time.Since(start).Seconds()
 }
+
+// UpdateEtcdDbSize sets the etcd_db_total_size_in_bytes metric.
+func UpdateEtcdDbSize(ep string, size int64) {
+	dbTotalSize.WithLabelValues(ep).Set(float64(size))
+}

pkg/storage/storagebackend/config.go

@@ -28,7 +28,8 @@ const (
 	StorageTypeUnset = ""
 	StorageTypeETCD3 = "etcd3"
 
-	DefaultCompactInterval = 5 * time.Minute
+	DefaultCompactInterval      = 5 * time.Minute
+	DefaultDBMetricPollInterval = 30 * time.Second
 )
 
 // TransportConfig holds all connection related info,  i.e. equal TransportConfig means equal servers we talk to.
@@ -71,13 +72,16 @@ type Config struct {
 	CompactionInterval time.Duration
 	// CountMetricPollPeriod specifies how often should count metric be updated
 	CountMetricPollPeriod time.Duration
+	// DBMetricPollInterval specifies how often should storage backend metric be updated.
+	DBMetricPollInterval time.Duration
 }
 
 func NewDefaultConfig(prefix string, codec runtime.Codec) *Config {
 	return &Config{
-		Paging:             true,
-		Prefix:             prefix,
-		Codec:              codec,
-		CompactionInterval: DefaultCompactInterval,
+		Paging:               true,
+		Prefix:               prefix,
+		Codec:                codec,
+		CompactionInterval:   DefaultCompactInterval,
+		DBMetricPollInterval: DefaultDBMetricPollInterval,
 	}
 }

pkg/storage/storagebackend/factory/etcd3.go

@@ -36,20 +36,26 @@ import (
 	"k8s.io/apiserver/pkg/server/egressselector"
 	"k8s.io/apiserver/pkg/storage"
 	"k8s.io/apiserver/pkg/storage/etcd3"
+	"k8s.io/apiserver/pkg/storage/etcd3/metrics"
 	"k8s.io/apiserver/pkg/storage/storagebackend"
 	"k8s.io/apiserver/pkg/storage/value"
 	"k8s.io/component-base/metrics/legacyregistry"
+	"k8s.io/klog"
 )
 
-// The short keepalive timeout and interval have been chosen to aggressively
-// detect a failed etcd server without introducing much overhead.
-const keepaliveTime = 30 * time.Second
-const keepaliveTimeout = 10 * time.Second
+const (
+	// The short keepalive timeout and interval have been chosen to aggressively
+	// detect a failed etcd server without introducing much overhead.
+	keepaliveTime    = 30 * time.Second
+	keepaliveTimeout = 10 * time.Second
 
-// dialTimeout is the timeout for failing to establish a connection.
-// It is set to 20 seconds as times shorter than that will cause TLS connections to fail
-// on heavily loaded arm64 CPUs (issue #64649)
-const dialTimeout = 20 * time.Second
+	// dialTimeout is the timeout for failing to establish a connection.
+	// It is set to 20 seconds as times shorter than that will cause TLS connections to fail
+	// on heavily loaded arm64 CPUs (issue #64649)
+	dialTimeout = 20 * time.Second
+
+	dbMetricsMonitorJitter = 0.5
+)
 
 func init() {
 	// grpcprom auto-registers (via an init function) their client metrics, since we are opting out of
@@ -57,6 +63,7 @@ func init() {
 	// we need to explicitly register these metrics to our global registry here.
 	// For reference: https://github.com/kubernetes/kubernetes/pull/81387
 	legacyregistry.RawMustRegister(grpcprom.DefaultClientMetrics)
+	dbMetricsMonitors = make(map[string]struct{})
 }
 
 func newETCD3HealthCheck(c storagebackend.Config) (func() error, error) {
@@ -153,16 +160,20 @@ type runningCompactor struct {
 }
 
 var (
-	lock       sync.Mutex
-	compactors = map[string]*runningCompactor{}
+	// compactorsMu guards access to compactors map
+	compactorsMu sync.Mutex
+	compactors   = map[string]*runningCompactor{}
+	// dbMetricsMonitorsMu guards access to dbMetricsMonitors map
+	dbMetricsMonitorsMu sync.Mutex
+	dbMetricsMonitors   map[string]struct{}
 )
 
 // startCompactorOnce start one compactor per transport. If the interval get smaller on repeated calls, the
 // compactor is replaced. A destroy func is returned. If all destroy funcs with the same transport are called,
 // the compactor is stopped.
 func startCompactorOnce(c storagebackend.TransportConfig, interval time.Duration) (func(), error) {
-	lock.Lock()
-	defer lock.Unlock()
+	compactorsMu.Lock()
+	defer compactorsMu.Unlock()
 
 	key := fmt.Sprintf("%v", c) // gives: {[server1 server2] keyFile certFile caFile}
 	if compactor, foundBefore := compactors[key]; !foundBefore || compactor.interval > interval {
@@ -193,8 +204,8 @@ func startCompactorOnce(c storagebackend.TransportConfig, interval time.Duration
 	compactors[key].refs++
 
 	return func() {
-		lock.Lock()
-		defer lock.Unlock()
+		compactorsMu.Lock()
+		defer compactorsMu.Unlock()
 
 		compactor := compactors[key]
 		compactor.refs--
@@ -218,6 +229,11 @@ func newETCD3Storage(c storagebackend.Config) (storage.Interface, DestroyFunc, e
 		return nil, nil, err
 	}
 
+	stopDBSizeMonitor, err := startDBSizeMonitorPerEndpoint(client, c.DBMetricPollInterval)
+	if err != nil {
+		return nil, nil, err
+	}
+
 	var once sync.Once
 	destroyFunc := func() {
 		// we know that storage destroy funcs are called multiple times (due to reuse in subresources).
@@ -225,6 +241,7 @@ func newETCD3Storage(c storagebackend.Config) (storage.Interface, DestroyFunc, e
 		// TODO: fix duplicated storage destroy calls higher level
 		once.Do(func() {
 			stopCompactor()
+			stopDBSizeMonitor()
 			client.Close()
 		})
 	}
@@ -234,3 +251,36 @@ func newETCD3Storage(c storagebackend.Config) (storage.Interface, DestroyFunc, e
 	}
 	return etcd3.New(client, c.Codec, c.Prefix, transformer, c.Paging), destroyFunc, nil
 }
+
+// startDBSizeMonitorPerEndpoint starts a loop to monitor etcd database size and update the
+// corresponding metric etcd_db_total_size_in_bytes for each etcd server endpoint.
+func startDBSizeMonitorPerEndpoint(client *clientv3.Client, interval time.Duration) (func(), error) {
+	if interval == 0 {
+		return func() {}, nil
+	}
+	dbMetricsMonitorsMu.Lock()
+	defer dbMetricsMonitorsMu.Unlock()
+
+	ctx, cancel := context.WithCancel(context.Background())
+	for _, ep := range client.Endpoints() {
+		if _, found := dbMetricsMonitors[ep]; found {
+			continue
+		}
+		dbMetricsMonitors[ep] = struct{}{}
+		endpoint := ep
+		klog.V(4).Infof("Start monitoring storage db size metric for endpoint %s with polling interval %v", endpoint, interval)
+		go wait.JitterUntilWithContext(ctx, func(context.Context) {
+			epStatus, err := client.Maintenance.Status(ctx, endpoint)
+			if err != nil {
+				klog.V(4).Infof("Failed to get storage db size for ep %s: %v", endpoint, err)
+				metrics.UpdateEtcdDbSize(endpoint, -1)
+			} else {
+				metrics.UpdateEtcdDbSize(endpoint, epStatus.DbSize)
+			}
+		}, interval, dbMetricsMonitorJitter, true)
+	}
+
+	return func() {
+		cancel()
+	}, nil
+}