Trace Support

entry.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"runtime"
 	"time"
 )
 
@@ -29,13 +30,17 @@ type Entry struct {
 
 	// Message passed to Debug, Info, Warn, Error, Fatal or Panic
 	Message string
+
+	// Trace information
+	Trace string
 }
 
 func NewEntry(logger *Logger) *Entry {
 	return &Entry{
 		Logger: logger,
 		// Default is three fields, give a little extra room
-		Data: make(Fields, 5),
+		Data:  make(Fields, 5),
+		Trace: "",
 	}
 }
 
@@ -78,13 +83,26 @@ func (entry *Entry) WithFields(fields Fields) *Entry {
 	return &Entry{Logger: entry.Logger, Data: data}
 }
 
+// WithTrace adds a stack trace back from where the log entry was created
+func (entry *Entry) WithTrace() *Entry {
+	// don't actually do the trace here otherwise it'll be wrong
+	entry.Trace = "placeholder"
+	return entry
+}
+
 // This function is not declared with a pointer value because otherwise
 // race conditions will occur when using multiple goroutines
 func (entry Entry) log(level Level, msg string) {
 	entry.Time = time.Now()
 	entry.Level = level
 	entry.Message = msg
 
+	if entry.Trace == "placeholder" {
+		stack := make([]byte, 2048)
+		size := runtime.Stack(stack, false)
+		entry.Trace = string(stack[:size])
+	}
+
 	if err := entry.Logger.Hooks.Fire(level, &entry); err != nil {
 		entry.Logger.mu.Lock()
 		fmt.Fprintf(os.Stderr, "Failed to fire hook: %v\n", err)

formatter.go

@@ -45,4 +45,9 @@ func prefixFieldClashes(data Fields) {
 	if ok {
 		data["fields.level"] = data["level"]
 	}
+
+	_, ok = data["trace"]
+	if ok {
+		data["fields.trace"] = data["trace"]
+	}
 }

json_formatter.go

@@ -33,6 +33,11 @@ func (f *JSONFormatter) Format(entry *Entry) ([]byte, error) {
 	data["msg"] = entry.Message
 	data["level"] = entry.Level.String()
 
+	// Only add trace if it was built
+	if entry.Trace != "" {
+		data["trace"] = entry.Trace
+	}
+
 	serialized, err := json.Marshal(data)
 	if err != nil {
 		return nil, fmt.Errorf("Failed to marshal fields to JSON, %v", err)

logger.go

@@ -64,6 +64,11 @@ func (logger *Logger) WithFields(fields Fields) *Entry {
 	return NewEntry(logger).WithFields(fields)
 }
 
+// WithTrace creates a new log entry with a captured trace from the current location
+func (logger *Logger) WithTrace() *Entry {
+	return NewEntry(logger).WithTrace()
+}
+
 func (logger *Logger) Debugf(format string, args ...interface{}) {
 	if logger.Level >= DebugLevel {
 		NewEntry(logger).Debugf(format, args...)

logrus_test.go

@@ -62,6 +62,7 @@ func TestPrint(t *testing.T) {
 	}, func(fields Fields) {
 		assert.Equal(t, fields["msg"], "test")
 		assert.Equal(t, fields["level"], "info")
+		assert.Nil(t, fields["trace"])
 	})
 }
 
@@ -71,6 +72,7 @@ func TestInfo(t *testing.T) {
 	}, func(fields Fields) {
 		assert.Equal(t, fields["msg"], "test")
 		assert.Equal(t, fields["level"], "info")
+		assert.Nil(t, fields["trace"])
 	})
 }
 
@@ -80,6 +82,17 @@ func TestWarn(t *testing.T) {
 	}, func(fields Fields) {
 		assert.Equal(t, fields["msg"], "test")
 		assert.Equal(t, fields["level"], "warning")
+		assert.Nil(t, fields["trace"])
+	})
+}
+
+func TestWithTrace(t *testing.T) {
+	LogAndAssertJSON(t, func(log *Logger) {
+		log.WithTrace().Warn("test")
+	}, func(fields Fields) {
+		assert.Equal(t, fields["msg"], "test")
+		assert.Equal(t, fields["level"], "warning")
+		assert.NotNil(t, fields["trace"])
 	})
 }