From 7aabe92d75a140e18b6043d4cb70cbe34cefcd59 Mon Sep 17 00:00:00 2001
From: Oleg Zaytsev <oleg@zaytsev.es>
Date: Thu, 21 Feb 2019 09:49:45 +0100
Subject: [PATCH] Added NoDebugLogger that doesn't format debug logs

fmt.Spritnf() is too expensive to call and debug logs are usually
disabled in prod, so we don't want to waste time formatting them.
---
 no_debug_logger.go            | 12 +++++++++
 no_debug_logger_bench_test.go | 50 +++++++++++++++++++++++++++++++++++
 2 files changed, 62 insertions(+)
 create mode 100644 no_debug_logger.go
 create mode 100644 no_debug_logger_bench_test.go

diff --git a/no_debug_logger.go b/no_debug_logger.go
new file mode 100644
index 0000000..cdd7105
--- /dev/null
+++ b/no_debug_logger.go
@@ -0,0 +1,12 @@
+package log
+
+// NoDebugLogger embeds a Logger, but in calls to debug functions it does nothing.
+// It avoids doing fmt.Sprintf() for those calls as they will be discarded anyways.
+// This makes those calls like 50 times faster (see benchmark file)
+type NoDebugLogger struct {
+	Logger
+}
+
+func (NoDebugLogger) Debug(args ...interface{})                 {}
+func (NoDebugLogger) Debugf(format string, args ...interface{}) {}
+func (NoDebugLogger) Debugln(args ...interface{})               {}
\ No newline at end of file
diff --git a/no_debug_logger_bench_test.go b/no_debug_logger_bench_test.go
new file mode 100644
index 0000000..19988da
--- /dev/null
+++ b/no_debug_logger_bench_test.go
@@ -0,0 +1,50 @@
+package log
+
+import (
+	"testing"
+)
+
+/*
+$ go test -bench=. ./...
+     | goos: darwin
+     | goarch: amd64
+     | pkg: github.com/cabify/go-logging
+     | BenchmarkPlainLoggerDebugSpeed-4      	30000000	        45.9 ns/op
+     | BenchmarkNoDebugLoggerDebugSpeed-4    	2000000000	         0.33 ns/op
+     | BenchmarkPlainLoggerDebugfSpeed-4     	20000000	        80.8 ns/op
+     | BenchmarkNoDebugLoggerDebugfSpeed-4   	50000000	        36.5 ns/op
+*/
+
+type someStruct struct {
+	value float64
+}
+
+var (
+	structValue           = someStruct{value: 10.0}
+	plainLoggerInstance   = NewLogger("test")
+	noDebugLoggerInstance = NoDebugLogger{Logger: plainLoggerInstance}
+)
+
+func BenchmarkPlainLoggerDebugSpeed(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		plainLoggerInstance.Debug("Something")
+	}
+}
+
+func BenchmarkNoDebugLoggerDebugSpeed(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		noDebugLoggerInstance.Debug("Something")
+	}
+}
+
+func BenchmarkPlainLoggerDebugfSpeed(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		plainLoggerInstance.Debugf("Something %v, %d", structValue, i)
+	}
+}
+
+func BenchmarkNoDebugLoggerDebugfSpeed(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		noDebugLoggerInstance.Debugf("Something %v, %d", structValue, i)
+	}
+}