Share a single etcd3 client logger across all clients

Currently the API server creates one etcd client per CRD. If clients
aren't provided a logger they'll each create their own. These loggers
can account for ~20% of API server memory consumption on a cluster with
hundreds of CRDs.

Signed-off-by: Nic Cope <nicc@rk0n.org>

Kubernetes-commit: 0c81eabb853e581abbcb37ebf094af3316e1012e

pkg/storage/storagebackend/factory/etcd3.go

@@ -27,10 +27,12 @@ import (
 	"time"
 
 	grpcprom "github.com/grpc-ecosystem/go-grpc-prometheus"
+	"go.etcd.io/etcd/client/pkg/v3/logutil"
 	"go.etcd.io/etcd/client/pkg/v3/transport"
 	clientv3 "go.etcd.io/etcd/client/v3"
 	"go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc"
 	"go.uber.org/zap"
+	"go.uber.org/zap/zapcore"
 	"google.golang.org/grpc"
 
 	"k8s.io/apimachinery/pkg/runtime"
@@ -64,6 +66,14 @@ const (
 	dbMetricsMonitorJitter = 0.5
 )
 
+// TODO(negz): Stop using a package scoped logger. At the time of writing we're
+// creating an etcd client for each CRD. We need to pass each etcd client a
+// logger or each client will create its own, which comes with a significant
+// memory cost (around 20% of the API server's memory when hundreds of CRDs are
+// present). The correct fix here is to not create a client per CRD. See
+// https://github.com/kubernetes/kubernetes/issues/111476 for more.
+var etcd3ClientLogger *zap.Logger
+
 func init() {
 	// grpcprom auto-registers (via an init function) their client metrics, since we are opting out of
 	// using the global prometheus registry and using our own wrapped global registry,
@@ -71,6 +81,12 @@ func init() {
 	// For reference: https://github.com/kubernetes/kubernetes/pull/81387
 	legacyregistry.RawMustRegister(grpcprom.DefaultClientMetrics)
 	dbMetricsMonitors = make(map[string]struct{})
+
+	l, err := logutil.CreateDefaultZapLogger(zapcore.InfoLevel)
+	if err != nil {
+		l = zap.NewNop()
+	}
+	etcd3ClientLogger = l
 }
 
 func newETCD3HealthCheck(c storagebackend.Config, stopCh <-chan struct{}) (func() error, error) {
@@ -217,6 +233,7 @@ var newETCD3Client = func(c storagebackend.TransportConfig) (*clientv3.Client, e
 		}
 		dialOptions = append(dialOptions, grpc.WithContextDialer(dialer))
 	}
+
 	cfg := clientv3.Config{
 		DialTimeout:          dialTimeout,
 		DialKeepAliveTime:    keepaliveTime,
@@ -224,10 +241,7 @@ var newETCD3Client = func(c storagebackend.TransportConfig) (*clientv3.Client, e
 		DialOptions:          dialOptions,
 		Endpoints:            c.ServerList,
 		TLS:                  tlsConfig,
-
-		// This logger uses a significant amount of memory when many CRDs (i.e.
-		// 1,000+) are added to the API server, so we disable it.
-		Logger: zap.NewNop(),
+		Logger:               etcd3ClientLogger,
 	}
 
 	return clientv3.New(cfg)