Add benchmark for logger

logger_bench_test.go

@@ -0,0 +1,37 @@
+package logrus
+
+import (
+	"os"
+	"testing"
+)
+
+// smallFields is a small size data set for benchmarking
+var loggerFields = Fields{
+	"foo":   "bar",
+	"baz":   "qux",
+	"one":   "two",
+	"three": "four",
+}
+
+func BenchmarkDummyLogger(b *testing.B) {
+	nullf, err := os.OpenFile("/dev/null", os.O_WRONLY, 0666)
+	if err != nil {
+		b.Fatalf("%v", err)
+	}
+	defer nullf.Close()
+	doLoggerBenchmark(b, nullf, &TextFormatter{DisableColors: true}, smallFields)
+}
+
+func doLoggerBenchmark(b *testing.B, out *os.File, formatter Formatter, fields Fields) {
+	logger := Logger{
+		Out:       out,
+		Level:     InfoLevel,
+		Formatter: formatter,
+	}
+	entry := logger.WithFields(fields)
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			entry.Info("aaa")
+		}
+	})
+}