fix(backend): added error log in kafka producer

ee/backend/pkg/kafka/producer.go

@@ -1,10 +1,11 @@
 package kafka
 
 import (
+	"fmt"
 	"log"
 
-	"openreplay/backend/pkg/env"
 	"gopkg.in/confluentinc/confluent-kafka-go.v1/kafka"
+	"openreplay/backend/pkg/env"
 )
 
 type Producer struct {
@@ -27,7 +28,20 @@ func NewProducer() *Producer {
 	if err != nil {
 		log.Fatalln(err)
 	}
-	return &Producer{producer}
+	newProducer := &Producer{producer}
+	go newProducer.errorHandler()
+	return newProducer
+}
+
+func (p *Producer) errorHandler() {
+	for e := range p.producer.Events() {
+		switch ev := e.(type) {
+		case *kafka.Message:
+			if ev.TopicPartition.Error != nil {
+				fmt.Printf("Delivery failed: topicPartition: %v, key: %d\n", ev.TopicPartition, decodeKey(ev.Key))
+			}
+		}
+	}
 }
 
 func (p *Producer) Produce(topic string, key uint64, value []byte) error {