Summarise key change logs (#1278)

keyserver/producers/keychange.go

@@ -42,6 +42,7 @@ func (p *KeyChange) DefaultPartition() int32 {
 
 // ProduceKeyChanges creates new change events for each key
 func (p *KeyChange) ProduceKeyChanges(keys []api.DeviceMessage) error {
+	userToDeviceCount := make(map[string]int)
 	for _, key := range keys {
 		var m sarama.ProducerMessage
 
@@ -62,12 +63,12 @@ func (p *KeyChange) ProduceKeyChanges(keys []api.DeviceMessage) error {
 		if err != nil {
 			return err
 		}
+		userToDeviceCount[key.UserID]++
+	}
+	for userID, count := range userToDeviceCount {
 		logrus.WithFields(logrus.Fields{
-			"user_id":       key.UserID,
-			"device_id":     key.DeviceID,
-			"partition":     partition,
-			"offset":        offset,
-			"len_key_bytes": len(key.KeyJSON),
+			"user_id":         userID,
+			"num_key_changes": count,
 		}).Infof("Produced to key change topic '%s'", p.Topic)
 	}
 	return nil