Logs: Prevent feedback loops by omitting repeated messages #2335

This also prevents debug and trace messages to be sent to the frontend.

internal/api/websocket.go

@@ -93,7 +93,11 @@ func wsReader(ws *websocket.Conn, writeMutex *sync.Mutex, connId string, conf *c
 func wsWriter(ws *websocket.Conn, writeMutex *sync.Mutex, connId string) {
 	pingTicker := time.NewTicker(15 * time.Second)
 	s := event.Subscribe(
-		"log.*",
+		"log.fatal",
+		"log.error",
+		"log.warning",
+		"log.warn",
+		"log.info",
 		"notify.*",
 		"index.*",
 		"upload.*",

internal/event/buffer.go

@@ -0,0 +1,28 @@
+package event
+
+import (
+	"bytes"
+	"sync"
+)
+
+// Buffer is a goroutine safe buffer.
+type Buffer struct {
+	buffer bytes.Buffer
+	mutex  sync.RWMutex
+}
+
+// Set updates the buffer content.
+func (b *Buffer) Set(s string) (err error) {
+	b.mutex.Lock()
+	defer b.mutex.Unlock()
+	b.buffer.Reset()
+	_, err = b.buffer.WriteString(s)
+	return err
+}
+
+// Get returns the buffer content.
+func (b *Buffer) Get() string {
+	b.mutex.RLock()
+	defer b.mutex.RUnlock()
+	return b.buffer.String()
+}

internal/event/buffer_test.go

@@ -0,0 +1,19 @@
+package event
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestBuffer(t *testing.T) {
+	b := Buffer{}
+
+	assert.Equal(t, "", b.Get())
+	assert.Equal(t, nil, b.Set("foo123 !!!"))
+	assert.Equal(t, "foo123 !!!", b.Get())
+	assert.Equal(t, nil, b.Set("BAR"))
+	assert.Equal(t, "BAR", b.Get())
+	assert.Equal(t, nil, b.Set(""))
+	assert.Equal(t, "", b.Get())
+}

internal/event/init.go

@@ -0,0 +1,21 @@
+package event
+
+import (
+	"os"
+
+	"github.com/sirupsen/logrus"
+)
+
+func init() {
+	hooks := logrus.LevelHooks{}
+	hooks.Add(NewHook(SharedHub()))
+
+	Log = &logrus.Logger{
+		Out:          os.Stderr,
+		Formatter:    &logrus.TextFormatter{},
+		Hooks:        hooks,
+		Level:        logrus.DebugLevel,
+		ExitFunc:     os.Exit,
+		ReportCaller: false,
+	}
+}

internal/event/log.go

@@ -1,23 +1,37 @@
 package event
 
 import (
-	"os"
+	"fmt"
 
 	"github.com/leandro-lugaresi/hub"
 	"github.com/sirupsen/logrus"
 )
 
 var Log *logrus.Logger
+var LastLog Buffer
 
+// Hook represents a log event hook.
 type Hook struct {
 	hub *hub.Hub
 }
 
+// NewHook creates a new log event hook.
 func NewHook(hub *hub.Hub) *Hook {
 	return &Hook{hub: hub}
 }
 
+// Fire publishes a new log event,
 func (h *Hook) Fire(entry *logrus.Entry) error {
+	if entry == nil {
+		return fmt.Errorf("log entry is empty")
+	} else if entry.Message == "" {
+		return fmt.Errorf("log message is empty")
+	} else if LastLog.Get() == entry.Message {
+		return nil
+	} else if err := LastLog.Set(entry.Message); err != nil {
+		return err
+	}
+
 	h.hub.Publish(Message{
 		Name: "log." + entry.Level.String(),
 		Fields: Data{
@@ -30,20 +44,7 @@ func (h *Hook) Fire(entry *logrus.Entry) error {
 	return nil
 }
 
+// Levels returns a slice containing all supported log levels.
 func (h *Hook) Levels() []logrus.Level {
 	return logrus.AllLevels
 }
-
-func init() {
-	hooks := logrus.LevelHooks{}
-	hooks.Add(NewHook(SharedHub()))
-
-	Log = &logrus.Logger{
-		Out:          os.Stderr,
-		Formatter:    &logrus.TextFormatter{},
-		Hooks:        hooks,
-		Level:        logrus.DebugLevel,
-		ExitFunc:     os.Exit,
-		ReportCaller: false,
-	}
-}