Add key for Kafka messages (fixes #4143) (#4151)

cmd/notify-kafka.go

@@ -17,8 +17,6 @@
 package cmd
 
 import (
-	"errors"
-	"fmt"
 	"io/ioutil"
 	"net"
 
@@ -27,6 +25,10 @@ import (
 	sarama "gopkg.in/Shopify/sarama.v1"
 )
 
+var (
+	kkErrFunc = newNotificationErrorFactory("Kafka")
+)
+
 // kafkaNotify holds the configuration of the Kafka server/cluster to
 // send notifications to.
 type kafkaNotify struct {
@@ -46,7 +48,7 @@ func (k *kafkaNotify) Validate() error {
 		return nil
 	}
 	if len(k.Brokers) == 0 {
-		return errors.New("No broker specified")
+		return kkErrFunc("No broker(s) specified.")
 	}
 	// Validate all specified brokers.
 	for _, brokerAddr := range k.Brokers {
@@ -70,8 +72,8 @@ func dialKafka(kn kafkaNotify) (kafkaConn, error) {
 	}
 
 	if kn.Topic == "" {
-		return kafkaConn{}, fmt.Errorf(
-			"Kafka Notifier Error: Topic was not specified in configuration")
+		return kafkaConn{}, kkErrFunc(
+			"Topic was not specified in configuration")
 	}
 
 	config := sarama.NewConfig()
@@ -83,10 +85,7 @@ func dialKafka(kn kafkaNotify) (kafkaConn, error) {
 
 	p, err := sarama.NewSyncProducer(kn.Brokers, config)
 	if err != nil {
-		return kafkaConn{}, fmt.Errorf(
-			"Kafka Notifier Error: Failed to start producer: %v",
-			err,
-		)
+		return kafkaConn{}, kkErrFunc("Failed to start producer: %v", err)
 	}
 
 	return kafkaConn{p, kn.Topic}, nil
@@ -121,16 +120,24 @@ func (kC kafkaConn) Fire(entry *logrus.Entry) error {
 		return err
 	}
 
+	// Extract the key of the event as a string
+	keyStr, ok := entry.Data["Key"].(string)
+	if !ok {
+		return kkErrFunc("Unable to convert event key %v to string.",
+			entry.Data["Key"])
+	}
+
 	// Construct message to send to Kafka
 	msg := sarama.ProducerMessage{
 		Topic: kC.topic,
+		Key:   sarama.StringEncoder(keyStr),
 		Value: sarama.ByteEncoder(body.Bytes()),
 	}
 
 	// Attempt sending the message to Kafka
 	_, _, err = kC.producer.SendMessage(&msg)
 	if err != nil {
-		return fmt.Errorf("Error sending event to Kafka - %v", err)
+		return kkErrFunc("Error sending event to Kafka - %v", err)
 	}
 	return nil
 }