fix log format

README.md

@@ -68,23 +68,21 @@ type Option struct {
 
     // optional: customize json payload builder
     Converter Converter
-	// optional: custom marshaler
-	Marshaler func(v any) ([]byte, error)
 
     // optional: see slog.HandlerOptions
     AddSource   bool
     ReplaceAttr func(groups []string, a slog.Attr) slog.Attr
 }
 ```
 
-Attributes will be injected in log payload.
+Attributes will be injected in log "extra".
 
 Other global parameters:
 
 ```go
 sloggraylog.SourceKey = "source"
-sloggraylog.ContextKey = "extra"
 sloggraylog.ErrorKeys = []string{"error", "err"}
+sloggraylog.LogLevels = map[slog.Level]int32{...}
 ```
 
 ### Example
@@ -105,6 +103,8 @@ func main() {
         log.Fatalf("gelf.NewWriter: %s", err)
     }
 
+	gelfWriter.CompressionType = gelf.CompressNone  // for debugging only
+
     logger := slog.New(sloggraylog.Option{Level: slog.LevelDebug, Writer: gelfWriter}.NewGraylogHandler())
     logger = logger.
         With("environment", "dev").
@@ -135,14 +135,14 @@ Output:
 ```json
 {
     "timestamp":"2023-04-10T14:00:0.000000+00:00",
-    "level":"ERROR",
+    "level":3,
     "message":"caramba!",
-    "error":{
-        "error":"could not count users",
-        "kind":"*errors.errorString",
-        "stack":null
-    },
     "extra":{
+        "error":{
+            "error":"could not count users",
+            "kind":"*errors.errorString",
+            "stack":null
+        },
         "environment":"dev",
         "release":"v1.0.0",
         "category":"sql",
@@ -154,9 +154,8 @@ Output:
 
 {
     "timestamp":"2023-04-10T14:00:0.000000+00:00",
-    "level":"INFO",
+    "level":6,
     "message":"user registration",
-    "error":null,
     "extra":{
         "environment":"dev",
         "release":"v1.0.0",

converter.go

@@ -7,12 +7,11 @@ import (
 )
 
 var SourceKey = "source"
-var ContextKey = "extra"
 var ErrorKeys = []string{"error", "err"}
 
-type Converter func(addSource bool, replaceAttr func(groups []string, a slog.Attr) slog.Attr, loggerAttr []slog.Attr, groups []string, record *slog.Record) map[string]any
+type Converter func(addSource bool, replaceAttr func(groups []string, a slog.Attr) slog.Attr, loggerAttr []slog.Attr, groups []string, record *slog.Record) (extra map[string]any)
 
-func DefaultConverter(addSource bool, replaceAttr func(groups []string, a slog.Attr) slog.Attr, loggerAttr []slog.Attr, groups []string, record *slog.Record) map[string]any {
+func DefaultConverter(addSource bool, replaceAttr func(groups []string, a slog.Attr) slog.Attr, loggerAttr []slog.Attr, groups []string, record *slog.Record) (extra map[string]any) {
 	// aggregate all attributes
 	attrs := slogcommon.AppendRecordAttrsToAttrs(loggerAttr, groups, record)
 
@@ -23,27 +22,16 @@ func DefaultConverter(addSource bool, replaceAttr func(groups []string, a slog.A
 	attrs = slogcommon.ReplaceAttrs(replaceAttr, []string{}, attrs...)
 
 	// handler formatter
-	log := map[string]any{
-		"logger.name":    name,
-		"logger.version": version,
-		"timestamp":      record.Time.UTC(),
-		"level":          record.Level.String(),
-		"message":        record.Message,
-	}
-
-	extra := slogcommon.AttrsToMap(attrs...)
+	extra = slogcommon.AttrsToMap(attrs...)
 
 	for _, errorKey := range ErrorKeys {
 		if v, ok := extra[errorKey]; ok {
 			if err, ok := v.(error); ok {
-				log[errorKey] = slogcommon.FormatError(err)
-				delete(extra, errorKey)
+				extra[errorKey] = slogcommon.FormatError(err)
 				break
 			}
 		}
 	}
 
-	log[ContextKey] = extra
-
-	return log
+	return extra
 }

example/example.go

@@ -20,6 +20,8 @@ func main() {
 		log.Fatalf("gelf.NewWriter: %s", err)
 	}
 
+	gelfWriter.CompressionType = gelf.CompressNone // for debugging only
+
 	logger := slog.New(sloggraylog.Option{Level: slog.LevelDebug, Writer: gelfWriter}.NewGraylogHandler())
 	logger = logger.With("release", "v1.0.0")
 
@@ -33,4 +35,6 @@ func main() {
 		With("environment", "dev").
 		With("error", fmt.Errorf("an error")).
 		Error("A message")
+
+	time.Sleep(1 * time.Second)
 }

graylog.go

@@ -1 +1,10 @@
 package sloggraylog
+
+import "log/slog"
+
+var LogLevels = map[slog.Level]int32{
+	slog.LevelDebug: 7,
+	slog.LevelInfo:  6,
+	slog.LevelWarn:  4,
+	slog.LevelError: 3,
+}

handler.go

@@ -2,7 +2,9 @@ package sloggraylog
 
 import (
 	"context"
-	"encoding/json"
+	"fmt"
+	"os"
+	"strings"
 
 	"log/slog"
 
@@ -19,12 +21,13 @@ type Option struct {
 
 	// optional: customize json payload builder
 	Converter Converter
-	// optional: custom marshaler
-	Marshaler func(v any) ([]byte, error)
 
 	// optional: see slog.HandlerOptions
 	AddSource   bool
 	ReplaceAttr func(groups []string, a slog.Attr) slog.Attr
+
+	// internal
+	hostname string
 }
 
 func (o Option) NewGraylogHandler() slog.Handler {
@@ -35,13 +38,16 @@ func (o Option) NewGraylogHandler() slog.Handler {
 	if o.Writer == nil {
 		panic("missing graylog connections")
 	}
+	if o.Writer.Facility == "" {
+		o.Writer.Facility = fmt.Sprintf("%s/%s", name, version)
+	}
 
 	if o.Converter == nil {
 		o.Converter = DefaultConverter
 	}
 
-	if o.Marshaler == nil {
-		o.Marshaler = json.Marshal
+	if hostname, err := os.Hostname(); err == nil {
+		o.hostname = hostname
 	}
 
 	return &GraylogHandler{
@@ -64,15 +70,21 @@ func (h *GraylogHandler) Enabled(_ context.Context, level slog.Level) bool {
 }
 
 func (h *GraylogHandler) Handle(ctx context.Context, record slog.Record) error {
-	message := h.option.Converter(h.option.AddSource, h.option.ReplaceAttr, h.attrs, h.groups, &record)
-
-	bytes, err := h.option.Marshaler(message)
-	if err != nil {
-		return err
+	extra := h.option.Converter(h.option.AddSource, h.option.ReplaceAttr, h.attrs, h.groups, &record)
+
+	msg := &gelf.Message{
+		Version:  "1.1",
+		Host:     h.option.hostname,
+		Short:    short(&record),
+		Full:     strings.TrimSpace(record.Message),
+		TimeUnix: float64(record.Time.Unix()),
+		Level:    LogLevels[record.Level],
+		Facility: h.option.Writer.Facility,
+		Extra:    extra,
 	}
 
 	go func() {
-		_, _ = h.option.Writer.Write(append(bytes, byte('\n')))
+		_ = h.option.Writer.WriteMessage(msg)
 	}()
 
 	return nil
@@ -93,3 +105,12 @@ func (h *GraylogHandler) WithGroup(name string) slog.Handler {
 		groups: append(h.groups, name),
 	}
 }
+
+func short(record *slog.Record) string {
+	msg := strings.TrimSpace(record.Message)
+	if i := strings.IndexRune(msg, '\n'); i > 0 {
+		return msg[:i]
+	}
+
+	return msg
+}