Show group instance IDs in describe consumer-group output

CHANGELOG.md

@@ -6,11 +6,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
-### Changed
-- Updated several dependencies and replaced abandoned avro schema registry lib with a new library
-
 ### Added
 - [#207](https://github.com/deviceinsight/kafkactl/pull/207) Allow configuring TLS for avro schema registry
+- [#193](https://github.com/deviceinsight/kafkactl/pull/193) Print group instance IDs in `describe consumer-group` command
 
 ## 5.0.6 - 2024-03-14
 

internal/consumergroups/consumer-group-operation.go

@@ -43,6 +43,7 @@ type partitionOffset struct {
 type consumerGroupMember struct {
 	ClientHost         string           `json:"clientHost" yaml:"clientHost"`
 	ClientID           string           `json:"clientId" yaml:"clientId"`
+	GroupInstanceID    string           `json:"groupInstanceId,omitempty" yaml:"groupInstanceId,omitempty"`
 	AssignedPartitions []topicPartition `json:"assignedPartitions" yaml:"assignedPartitions"`
 }
 
@@ -73,11 +74,12 @@ type ConsumerGroupOperation struct {
 func (operation *ConsumerGroupOperation) DescribeConsumerGroup(flags DescribeConsumerGroupFlags, group string) error {
 
 	var (
-		err          error
-		ctx          internal.ClientContext
-		client       sarama.Client
-		admin        sarama.ClusterAdmin
-		descriptions []*sarama.GroupDescription
+		err                     error
+		ctx                     internal.ClientContext
+		client                  sarama.Client
+		admin                   sarama.ClusterAdmin
+		descriptions            []*sarama.GroupDescription
+		supportsGroupInstanceID bool
 	)
 
 	if ctx, err = internal.CreateClientContext(); err != nil {
@@ -88,6 +90,8 @@ func (operation *ConsumerGroupOperation) DescribeConsumerGroup(flags DescribeCon
 		return errors.Wrap(err, "failed to create client")
 	}
 
+	supportsGroupInstanceID = client.Config().Version.IsAtLeast(sarama.V2_4_0_0)
+
 	if admin, err = internal.CreateClusterAdmin(&ctx); err != nil {
 		return errors.Wrap(err, "failed to create cluster admin")
 	}
@@ -138,7 +142,7 @@ func (operation *ConsumerGroupOperation) DescribeConsumerGroup(flags DescribeCon
 
 			assignedPartitions := filterAssignedPartitions(memberAssignment.Topics, topicPartitions)
 
-			consumerGroupDescription.Members = addMember(consumerGroupDescription.Members, member.ClientHost, member.ClientId, assignedPartitions)
+			consumerGroupDescription.Members = addMember(consumerGroupDescription.Members, member.ClientHost, member.ClientId, member.GroupInstanceId, assignedPartitions)
 		}
 
 		sort.Slice(consumerGroupDescription.Members, func(i, j int) bool {
@@ -173,14 +177,30 @@ func (operation *ConsumerGroupOperation) DescribeConsumerGroup(flags DescribeCon
 			consumerGroupDescription.Members = nil
 		} else if flags.OutputFormat == "wide" || flags.OutputFormat == "" {
 			tableWriter := output.CreateTableWriter()
-			if err := tableWriter.WriteHeader("CLIENT_HOST", "CLIENT_ID", "TOPIC", "ASSIGNED_PARTITIONS"); err != nil {
+
+			columns := make([]string, 0, 5)
+			columns = append(columns, "CLIENT_HOST", "CLIENT_ID")
+			if supportsGroupInstanceID {
+				columns = append(columns, "GROUP_INSTANCE_ID")
+			}
+			columns = append(columns, "TOPIC", "ASSIGNED_PARTITIONS")
+
+			if err := tableWriter.WriteHeader(columns...); err != nil {
 				return err
 			}
 
 			for _, m := range consumerGroupDescription.Members {
 				for _, topic := range m.AssignedPartitions {
 					partitions := strings.Trim(strings.Join(strings.Fields(fmt.Sprint(topic.Partitions)), ","), "[]")
-					if err := tableWriter.Write(m.ClientHost, m.ClientID, topic.Name, partitions); err != nil {
+
+					columns = columns[:0]
+					columns = append(columns, m.ClientHost, m.ClientID)
+					if supportsGroupInstanceID {
+						columns = append(columns, m.GroupInstanceID)
+					}
+					columns = append(columns, topic.Name, partitions)
+
+					if err := tableWriter.Write(columns...); err != nil {
 						return err
 					}
 				}
@@ -226,7 +246,7 @@ func filterAssignedPartitions(assignedPartitions map[string][]int32, topicPartit
 	return result
 }
 
-func addMember(members []consumerGroupMember, clientHost string, clientID string, assignedPartitions map[string][]int32) []consumerGroupMember {
+func addMember(members []consumerGroupMember, clientHost string, clientID string, groupInstanceID *string, assignedPartitions map[string][]int32) []consumerGroupMember {
 
 	topicPartitionList := make([]topicPartition, 0)
 
@@ -247,7 +267,13 @@ func addMember(members []consumerGroupMember, clientHost string, clientID string
 	if len(assignedPartitions) == 0 {
 		return members
 	}
-	member := consumerGroupMember{ClientHost: clientHost, ClientID: clientID, AssignedPartitions: topicPartitionList}
+
+	groupInstanceIDString := ""
+	if groupInstanceID != nil {
+		groupInstanceIDString = *groupInstanceID
+	}
+
+	member := consumerGroupMember{ClientHost: clientHost, ClientID: clientID, GroupInstanceID: groupInstanceIDString, AssignedPartitions: topicPartitionList}
 	return append(members, member)
 }