Add custom object encoders for the set of string and namespaced name (#1309)

* Add custom object encoders for the set of string and namespaced name

In future we might add more (endpoints is a really good candidate)

* switch NN logging

* usage

* nn without ns

* nit

logging/object_encoders.go

@@ -0,0 +1,59 @@
+/*
+Copyright 2020 The Knative 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 logging
+
+import (
+	"strings"
+
+	"go.uber.org/zap/zapcore"
+
+	"k8s.io/apimachinery/pkg/types"
+	"k8s.io/apimachinery/pkg/util/sets"
+)
+
+// This file contains the specific object encoders for use in Knative
+// to optimize logging experience and performance.
+
+// StringSet returns a marshaler for the set of strings.
+// To use this in sugared logger do:
+//	logger.Infow("Revision State", zap.Object("healthy", logging.StringSet(healthySet)),
+//		zap.Object("unhealthy", logging.StringSet(unhealthySet)))
+// To use with non-sugared logger do:
+//	logger.Info("Revision State", zap.Object("healthy", logging.StringSet(healthySet)),
+//		zap.Object("unhealthy", logging.StringSet(unhealthySet)))
+func StringSet(s sets.String) zapcore.ObjectMarshalerFunc {
+	return func(enc zapcore.ObjectEncoder) error {
+		enc.AddString("keys", strings.Join(s.UnsortedList(), ","))
+		return nil
+	}
+}
+
+// NamespacedName returns a marshaler for NamespacedName.
+// To use this in sugared logger do:
+//	logger.Infow("Enqueuing", zap.Object("key", logging.NamespacedName(n)))
+// To use with non-sugared logger do:
+//	logger.Info("Enqueuing", zap.Object("key", logging.NamespacedName(n)))
+func NamespacedName(n types.NamespacedName) zapcore.ObjectMarshalerFunc {
+	return func(enc zapcore.ObjectEncoder) error {
+		if n.Namespace != "" {
+			enc.AddString("key", n.Name)
+		} else {
+			enc.AddString("key", n.Namespace+"/"+n.Name)
+		}
+		return nil
+	}
+}