From 25b8c546a0ff396e8e15575e3218e7e3585ac902 Mon Sep 17 00:00:00 2001
From: Pires <pjpires@gmail.com>
Date: Thu, 14 Jan 2021 22:41:45 +0000
Subject: [PATCH] log: process fields only on first klog call

Signed-off-by: Pires <pjpires@gmail.com>
---
 log/klogv2/klogv2.go      | 50 ++++++++++++++++++++++----------
 log/klogv2/klogv2_test.go | 60 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 95 insertions(+), 15 deletions(-)
 create mode 100644 log/klogv2/klogv2_test.go

diff --git a/log/klogv2/klogv2.go b/log/klogv2/klogv2.go
index cc54729f3..f34739d5f 100644
--- a/log/klogv2/klogv2.go
+++ b/log/klogv2/klogv2.go
@@ -24,6 +24,7 @@ import (
 	"fmt"
 	"sort"
 	"strings"
+	"sync"
 
 	"github.com/virtual-kubelet/virtual-kubelet/log"
 	"k8s.io/klog/v2"
@@ -32,17 +33,36 @@ import (
 // Ensure log.Logger is fully implemented during compile time.
 var _ log.Logger = (*adapter)(nil)
 
+type fieldMap struct {
+	log.Fields
+	processedFields string
+	sync.Once
+}
+
+func (f *fieldMap) String() string {
+	// Process if not processed before.
+	f.Do(func() {
+		// Only process if any fields have been set.
+		if len(f.Fields) > 0 && len(f.processedFields) == 0 {
+			f.processedFields = processFields(f.Fields)
+		}
+	})
+
+	return f.processedFields
+}
+
 // adapter implements the `log.Logger` interface for klogv2
 type adapter struct {
-	rawFields map[string]interface{}
-	fields    string
+	fields fieldMap
 }
 
 // New creates a new `log.Logger` from the provided entry
-func New(fields map[string]interface{}) log.Logger {
+func New(fields log.Fields) log.Logger {
+	if fields == nil {
+		fields = make(log.Fields)
+	}
 	return &adapter{
-		rawFields: fields,
-		fields:    processFields(fields),
+		fields: fieldMap{Fields: fields},
 	}
 }
 
@@ -59,43 +79,43 @@ func (l *adapter) Debugf(format string, args ...interface{}) {
 }
 
 func (l *adapter) Info(args ...interface{}) {
-	args = append(args, l.fields)
+	args = append(args, l.fields.String())
 	klog.InfoDepth(1, args...)
 }
 
 func (l *adapter) Infof(format string, args ...interface{}) {
 	formattedArgs := fmt.Sprintf(format, args...)
-	klog.InfoDepth(1, formattedArgs, l.fields)
+	klog.InfoDepth(1, formattedArgs, l.fields.String())
 }
 
 func (l *adapter) Warn(args ...interface{}) {
-	args = append(args, l.fields)
+	args = append(args, l.fields.String())
 	klog.WarningDepth(1, args...)
 }
 
 func (l *adapter) Warnf(format string, args ...interface{}) {
 	formattedArgs := fmt.Sprintf(format, args...)
-	klog.WarningDepth(1, formattedArgs, l.fields)
+	klog.WarningDepth(1, formattedArgs, l.fields.String())
 }
 
 func (l *adapter) Error(args ...interface{}) {
-	args = append(args, l.fields)
+	args = append(args, l.fields.String())
 	klog.ErrorDepth(1, args...)
 }
 
 func (l *adapter) Errorf(format string, args ...interface{}) {
 	formattedArgs := fmt.Sprintf(format, args...)
-	klog.ErrorDepth(1, formattedArgs, l.fields)
+	klog.ErrorDepth(1, formattedArgs, l.fields.String())
 }
 
 func (l *adapter) Fatal(args ...interface{}) {
-	args = append(args, l.fields)
+	args = append(args, l.fields.String())
 	klog.FatalDepth(1, args...)
 }
 
 func (l *adapter) Fatalf(format string, args ...interface{}) {
 	formattedArgs := fmt.Sprintf(format, args...)
-	klog.FatalDepth(1, formattedArgs, l.fields)
+	klog.FatalDepth(1, formattedArgs, l.fields.String())
 }
 
 // WithField adds a field to the log entry.
@@ -106,8 +126,8 @@ func (l *adapter) WithField(key string, val interface{}) log.Logger {
 // WithFields adds multiple fields to a log entry.
 func (l *adapter) WithFields(fields log.Fields) log.Logger {
 	// Clone existing fields.
-	newFields := make(map[string]interface{})
-	for k, v := range l.rawFields {
+	newFields := make(log.Fields)
+	for k, v := range l.fields.Fields {
 		newFields[k] = v
 	}
 	// Append new fields.
diff --git a/log/klogv2/klogv2_test.go b/log/klogv2/klogv2_test.go
new file mode 100644
index 000000000..85c6fd169
--- /dev/null
+++ b/log/klogv2/klogv2_test.go
@@ -0,0 +1,60 @@
+// Copyright © 2021 The virtual-kubelet 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 klogv2
+
+import (
+	"testing"
+
+	"github.com/virtual-kubelet/virtual-kubelet/log"
+)
+
+func TestFieldMap_String(t *testing.T) {
+	var tests = []struct {
+		fields   fieldMap
+		expected string
+	}{
+		{
+			fieldMap{Fields: nil},
+			"",
+		},
+		{
+			fieldMap{Fields: make(log.Fields)},
+			"",
+		},
+		{
+			fieldMap{Fields: map[string]interface{}{"one": 1}},
+			" [one=1]",
+		},
+		{
+			fieldMap{Fields: map[string]interface{}{"one": 1, "two": 2}},
+			" [one=1 two=2]",
+		},
+	}
+
+	for _, tt := range tests {
+		// Assert fields haven't been processed yet.
+		if len(tt.fields.processedFields) > 0 {
+			t.Fatal("fields shouldn't have been processed yet")
+		}
+		// Assert fields have been processed, if any.
+		actual := tt.fields.String()
+		if len(tt.fields.Fields) > 0 && len(tt.fields.processedFields) == 0 {
+			t.Fatal("fields should have been processed by now")
+		}
+		// Assert processFields yields desired results.
+		if actual != tt.expected {
+			t.Fatalf("expected: %s, got: %s", actual, tt.expected)
+		}
+	}
+}