fix: prevent panic on double close of data channel in batcher

- Add alreadyClosed flag to track if data channel was closed unexpectedly
- Skip closing data channel in defer if already closed
- Add unit test TestBatcher_UnexpectedChannelClose to verify the fix

pkg/tools/batcher/batcher.go

@@ -151,12 +151,15 @@ func (b *Batcher[T]) Put(ctx context.Context, data *T) error {
 
 func (b *Batcher[T]) scheduler() {
 	ticker := time.NewTicker(b.config.interval)
+	alreadyClosed := false
 	defer func() {
 		ticker.Stop()
 		for _, ch := range b.chArrays {
 			close(ch)
 		}
-		close(b.data)
+		if !alreadyClosed {
+			close(b.data)
+		}
 		b.wait.Done()
 	}()
 
@@ -169,6 +172,7 @@ func (b *Batcher[T]) scheduler() {
 		case data, ok := <-b.data:
 			if !ok {
 				// If the data channel is closed unexpectedly
+				alreadyClosed = true
 				return
 			}
 			if data == nil {

pkg/tools/batcher/batcher_test.go

@@ -3,9 +3,10 @@ package batcher
 import (
 	"context"
 	"fmt"
-	"github.com/openimsdk/tools/utils/stringutil"
 	"testing"
 	"time"
+
+	"github.com/openimsdk/tools/utils/stringutil"
 )
 
 func TestBatcher(t *testing.T) {
@@ -64,3 +65,54 @@ func TestBatcher(t *testing.T) {
 		t.Error("Data channel should be empty after closing")
 	}
 }
+
+func TestBatcher_UnexpectedChannelClose(t *testing.T) {
+	config := Config{
+		size:     100,
+		buffer:   10,
+		worker:   2,
+		interval: 50 * time.Millisecond,
+	}
+
+	b := New[string](
+		WithSize(config.size),
+		WithBuffer(config.buffer),
+		WithWorker(config.worker),
+		WithInterval(config.interval),
+	)
+
+	processedCount := 0
+	b.Do = func(ctx context.Context, channelID int, vals *Msg[string]) {
+		processedCount += len(vals.Val())
+	}
+	b.Sharding = func(key string) int {
+		hashCode := stringutil.GetHashCode(key)
+		return int(hashCode) % config.worker
+	}
+	b.Key = func(data *string) string {
+		return *data
+	}
+
+	err := b.Start()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Put some data
+	for i := 0; i < 50; i++ {
+		data := fmt.Sprintf("data%d", i)
+		if err := b.Put(context.Background(), &data); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	// Simulate unexpected channel close by closing the data channel directly
+	// This tests the alreadyClosed flag logic to prevent double close panic
+	close(b.data)
+
+	// Wait for scheduler to detect the closed channel and exit gracefully
+	b.wait.Wait()
+
+	t.Logf("Processed %d items before unexpected close", processedCount)
+	t.Log("Batcher handled unexpected channel close gracefully without panic")
+}