Fix the kafka panic when sending the message to a closed channel (mil…

…vus-io#25116) (milvus-io#25117)

Signed-off-by: SimFG <bang.fu@zilliz.com>

pkg/mq/msgstream/mqwrapper/kafka/kafka_producer.go

@@ -7,20 +7,20 @@ import (
 	"time"
 
 	"github.com/confluentinc/confluent-kafka-go/kafka"
-	"go.uber.org/zap"
-
 	"github.com/milvus-io/milvus/pkg/common"
 	"github.com/milvus-io/milvus/pkg/log"
 	"github.com/milvus-io/milvus/pkg/metrics"
 	"github.com/milvus-io/milvus/pkg/mq/msgstream/mqwrapper"
 	"github.com/milvus-io/milvus/pkg/util/timerecord"
+	"go.uber.org/zap"
 )
 
 type kafkaProducer struct {
 	p            *kafka.Producer
 	topic        string
 	deliveryChan chan kafka.Event
 	closeOnce    sync.Once
+	isClosed     bool
 }
 
 func (kp *kafkaProducer) Topic() string {
@@ -31,6 +31,12 @@ func (kp *kafkaProducer) Send(ctx context.Context, message *mqwrapper.ProducerMe
 	start := timerecord.NewTimeRecorder("send msg to stream")
 	metrics.MsgStreamOpCounter.WithLabelValues(metrics.SendMsgLabel, metrics.TotalLabel).Inc()
 
+	if kp.isClosed {
+		metrics.MsgStreamOpCounter.WithLabelValues(metrics.SendMsgLabel, metrics.FailLabel).Inc()
+		log.Error("kafka produce message fail because the producer has been closed", zap.String("topic", kp.topic))
+		return nil, common.NewIgnorableError(fmt.Errorf("kafka producer is closed"))
+	}
+
 	headers := make([]kafka.Header, 0, len(message.Properties))
 	for key, value := range message.Properties {
 		header := kafka.Header{Key: key, Value: []byte(value)}
@@ -69,9 +75,14 @@ func (kp *kafkaProducer) Send(ctx context.Context, message *mqwrapper.ProducerMe
 
 func (kp *kafkaProducer) Close() {
 	kp.closeOnce.Do(func() {
+		kp.isClosed = true
+
 		start := time.Now()
 		//flush in-flight msg within queue.
-		kp.p.Flush(10000)
+		i := kp.p.Flush(10000)
+		if i > 0 {
+			log.Warn("There are still un-flushed outstanding events", zap.Int("event_num", i), zap.Any("topic", kp.topic))
+		}
 
 		close(kp.deliveryChan)
 

pkg/mq/msgstream/mqwrapper/kafka/kafka_producer_test.go

@@ -67,3 +67,30 @@ func TestKafkaProducer_SendFail(t *testing.T) {
 		producer.Close()
 	}
 }
+
+func TestKafkaProducer_SendFailAfterClose(t *testing.T) {
+	kafkaAddress := getKafkaBrokerList()
+	kc := NewKafkaClientInstance(kafkaAddress)
+	defer kc.Close()
+	assert.NotNil(t, kc)
+
+	rand.Seed(time.Now().UnixNano())
+	topic := fmt.Sprintf("test-topic-%d", rand.Int())
+
+	producer, err := kc.CreateProducer(mqwrapper.ProducerOptions{Topic: topic})
+	assert.Nil(t, err)
+	assert.NotNil(t, producer)
+
+	producer.Close()
+
+	kafkaProd := producer.(*kafkaProducer)
+	assert.Equal(t, kafkaProd.Topic(), topic)
+
+	msg2 := &mqwrapper.ProducerMessage{
+		Payload:    []byte{},
+		Properties: map[string]string{},
+	}
+	_, err = producer.Send(context.TODO(), msg2)
+	time.Sleep(10 * time.Second)
+	assert.NotNil(t, err)
+}