Add error log when tsafe register watcher more than once (#16294)

Add some test case to cover the error case
Add log in error branch

Signed-off-by: Congqi Xia <congqi.xia@zilliz.com>

internal/querynode/tsafe.go

@@ -20,7 +20,9 @@ import (
 	"fmt"
 	"sync"
 
+	"github.com/milvus-io/milvus/internal/log"
 	"github.com/milvus-io/milvus/internal/util/typeutil"
+	"go.uber.org/zap"
 )
 
 type tSafeWatcher struct {
@@ -67,6 +69,7 @@ func (ts *tSafe) registerTSafeWatcher(t *tSafeWatcher) error {
 	ts.tSafeMu.Lock()
 	defer ts.tSafeMu.Unlock()
 	if ts.watcher != nil {
+		log.Warn("tSafeWatcher register more than once", zap.String("channel", ts.channel))
 		return fmt.Errorf("tSafeWatcher has been existed, channel = %s", ts.channel)
 	}
 	ts.watcher = t

internal/querynode/tsafe_test.go

@@ -63,3 +63,21 @@ func TestTSafe_TSafe(t *testing.T) {
 	timestamp = safe.get()
 	assert.Equal(t, targetTimestamp, timestamp)
 }
+
+func TestTSafe_Dup(t *testing.T) {
+	safe := newTSafe("TestTSafe-channel")
+	assert.NotNil(t, safe)
+
+	timestamp := safe.get()
+	assert.Equal(t, typeutil.ZeroTimestamp, timestamp)
+
+	watcher := newTSafeWatcher()
+	defer watcher.close()
+	assert.NotNil(t, watcher)
+
+	err := safe.registerTSafeWatcher(watcher)
+	assert.NoError(t, err)
+
+	err = safe.registerTSafeWatcher(watcher)
+	assert.Error(t, err)
+}