Listing consumer groups (#442)

* moved the existing note in section 3 to the beginning and added new section for Listing consumer groups using the CLI.

* updated the Listing consumer groups with subsections to improve the structure

* removed duplication

* replaced alternatively with in  addition

Author: fmcdonal

docs/kafka/consumer-configuration-kafka/README.adoc

@@ -68,22 +68,45 @@ Consumers within a group don’t read data from the same partition, but can read
 As a developer of applications and services, you can view all the consumer groups that have access to a particular Kafka instance in {product-kafka}.
 If required, use the {product-kafka} web console to reset the offsets of consumer groups or delete consumer groups.
 
-As an alternative to using the {product-kafka} web console, you can use the `rhoas` command-line interface (CLI) or the Kafka `kafka-consumer-groups.sh` script to review and update consumer groups.
+//Additional line break to resolve mod docs generation error
+[id="con-consumer-group-list_{context}"]
+== Listing consumer groups
+
+[role="_abstract"]
+In addition to the {product-kafka} web console, you can use the `rhoas` command-line interface (CLI) or the Kafka `kafka-consumer-groups.sh` script to list consumer groups for your Kafka instance. The following subsections describe how to use these methods to list consumer groups.
 
 ifndef::community[]
 NOTE: The Kafka scripts are part of the open source community version of Apache Kafka. The scripts are not a part of {product-kafka} and are therefore not supported by Red Hat.
 endif::[]
 
-//Additional line break to resolve mod docs generation error
+
+[id="con-consumer-group-list-using-CLI_{context}"]
+=== Listing consumer groups using the CLI
+
+To use the `rhoas` command-line interface (CLI) to list the consumer groups defined for your Kafka instance, enter the following command:
+
+
+[source,subs="+quotes,+attributes"]
+----
+rhoas kafka consumer-group list
+----
+
+When you enter the preceding command, you should see output similar to the following example:
+
+[source,subs="+quotes,+attributes"]
+----
+CONSUMER GROUP ID    ACTIVE MEMBERS    PARTITIONS WITH LAG
+-------------------  ----------------  ---------------------
+consumergroup1                     2                     0
+consumergroup2                     1                     0
+----
 
 [id="con-consumer-group-script_{context}"]
-== Connecting the Kafka consumer group script
+=== Connecting the Kafka consumer group script
 
 [role="_abstract"]
-If you're using the `kafka-consumer-groups.sh` script, or any other Kafka scripts,
-you'll need to use the `--bootstrap-server` and `--command-config` flags to connect to your Kafka instance.
+You can list consumer groups using the `kafka-consumer-groups.sh` script. To use this or any other Kafka scripts, you need to specify the `--bootstrap-server` and `--command-config` flags to connect to your Kafka instance. To list consumer groups, enter the following command:
 
-.Command to list all consumer groups
 [source,subs="+quotes,+attributes"]
 ----
 ./kafka-consumer-groups.sh --bootstrap-server __<bootstrap_server>__ --command-config __<authentication_properties>__ --list