From 736a1cea482e3dc223c20abce9d86e1bdd75216f Mon Sep 17 00:00:00 2001
From: Masahiro Sano <sabottenda@gmail.com>
Date: Sat, 13 Feb 2016 20:42:11 +0900
Subject: [PATCH] add LTSV logger

---
 log/ltsv_logger.go      | 80 +++++++++++++++++++++++++++++++++++++++++
 log/ltsv_logger_test.go | 78 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 158 insertions(+)
 create mode 100644 log/ltsv_logger.go
 create mode 100644 log/ltsv_logger_test.go

diff --git a/log/ltsv_logger.go b/log/ltsv_logger.go
new file mode 100644
index 000000000..803d65bd7
--- /dev/null
+++ b/log/ltsv_logger.go
@@ -0,0 +1,80 @@
+package log
+
+import (
+	"fmt"
+	"github.com/najeira/ltsv"
+	"io"
+	"reflect"
+)
+
+type ltsvLogger struct {
+	w io.Writer
+}
+
+// NewLTSVLogger returns a Logger that encodes keyvals to the Writer as
+// Labeled Tab-separated Values format.
+func NewLTSVLogger(w io.Writer) Logger {
+	return &ltsvLogger{
+		w: w,
+	}
+}
+
+func (l *ltsvLogger) Log(keyvals ...interface{}) error {
+	n := (len(keyvals) + 1) / 2 // +1 to handle case when len is odd
+	m := make(map[string]string, n)
+	for i := 0; i < len(keyvals); i += 2 {
+		k := keyvals[i]
+		var v interface{} = ErrMissingValue
+		if i+1 < len(keyvals) {
+			v = keyvals[i+1]
+		}
+		mergeStringMap(m, k, v)
+	}
+
+	w := ltsv.NewWriter(l.w)
+	if err := w.Write(m); err != nil {
+		return err
+	}
+	w.Flush()
+	return nil
+}
+
+func mergeStringMap(dst map[string]string, k, v interface{}) {
+	var key string
+	switch x := k.(type) {
+	case string:
+		key = x
+	case fmt.Stringer:
+		key = safeString(x)
+	default:
+		key = fmt.Sprint(x)
+	}
+
+	var val string
+	switch x := v.(type) {
+	case string:
+		val = x
+	case error:
+		val = safeErrorString(x)
+	case fmt.Stringer:
+		val = safeString(x)
+	default:
+		val = fmt.Sprint(x)
+	}
+
+	dst[key] = val
+}
+
+func safeErrorString(err error) (s string) {
+	defer func() {
+		if panicVal := recover(); panicVal != nil {
+			if v := reflect.ValueOf(err); v.Kind() == reflect.Ptr && v.IsNil() {
+				s = ""
+			} else {
+				panic(panicVal)
+			}
+		}
+	}()
+	s = err.Error()
+	return
+}
diff --git a/log/ltsv_logger_test.go b/log/ltsv_logger_test.go
new file mode 100644
index 000000000..69c914523
--- /dev/null
+++ b/log/ltsv_logger_test.go
@@ -0,0 +1,78 @@
+package log_test
+
+import (
+	"bytes"
+	"errors"
+	"io/ioutil"
+	"sort"
+	"strings"
+	"testing"
+
+	"github.com/go-kit/kit/log"
+)
+
+func TestLTSVLogger(t *testing.T) {
+	t.Parallel()
+	buf := &bytes.Buffer{}
+	logger := log.NewLTSVLogger(buf)
+	if err := logger.Log("err", errors.New("err"), "m", map[string]int{"0": 0}, "a", []int{1, 2, 3}); err != nil {
+		t.Fatal(err)
+	}
+
+	if want, have := "\n", buf.String(); !strings.HasSuffix(have, want) {
+		t.Errorf("must end with %q, got %#v", want, have)
+	}
+
+	values := strings.Split(strings.TrimSpace(buf.String()), "\t")
+	sort.Strings(values)
+
+	if want, have := "a:[1 2 3]", values[0]; want != have {
+		t.Errorf("\nwant %#v\nhave %#v", want, have)
+	}
+
+	if want, have := "err:err", values[1]; want != have {
+		t.Errorf("\nwant %#v\nhave %#v", want, have)
+	}
+
+	if want, have := "m:map[0:0]", values[2]; want != have {
+		t.Errorf("\nwant %#v\nhave %#v", want, have)
+	}
+}
+
+func TestLTSVLoggerNilStringerKey(t *testing.T) {
+	t.Parallel()
+
+	buf := &bytes.Buffer{}
+	logger := log.NewLTSVLogger(buf)
+	if err := logger.Log((*stringer)(nil), "v"); err != nil {
+		t.Fatal(err)
+	}
+	if want, have := "NULL:v\n", buf.String(); want != have {
+		t.Errorf("\nwant %#v\nhave %#v", want, have)
+	}
+}
+
+func TestLTSVLoggerNilErrorValue(t *testing.T) {
+	t.Parallel()
+
+	buf := &bytes.Buffer{}
+	logger := log.NewLTSVLogger(buf)
+	if err := logger.Log("err", (*stringError)(nil)); err != nil {
+		t.Fatal(err)
+	}
+	if want, have := "err:\n", buf.String(); want != have {
+		t.Errorf("\nwant %#v\nhave %#v", want, have)
+	}
+}
+
+func BenchmarkLTSVLoggerSimple(b *testing.B) {
+	benchmarkRunner(b, log.NewLTSVLogger(ioutil.Discard), baseMessage)
+}
+
+func BenchmarkLTSVLoggerContextual(b *testing.B) {
+	benchmarkRunner(b, log.NewLTSVLogger(ioutil.Discard), withMessage)
+}
+
+func TestLTSVLoggerConcurrency(t *testing.T) {
+	testConcurrency(t, log.NewLTSVLogger(ioutil.Discard))
+}