examples: Improve kafka example with more functionality (#1019)

Signed-off-by: Ryan Northey <ryan@synca.io>

Author: phlax

kafka/example.rst

@@ -125,6 +125,84 @@ Envoy also records cluster stats for the Kafka service:
   cluster.kafka_service.membership_healthy: 1
   cluster.kafka_service.membership_total: 1
 
+
+Step 8: Test consumer groups
+****************************
+
+Consumer groups allow multiple consumers to coordinate consumption of a topic.
+When consumers join a group, they use the Kafka group coordination protocol
+which Envoy proxies transparently.
+
+Start a consumer in a group. It will wait for messages and then exit after
+a timeout:
+
+.. code-block:: console
+
+   $ docker compose run --rm kafka-client \
+       kafka-console-consumer --bootstrap-server proxy:10000 \
+           --topic $TOPIC --group test-group --timeout-ms 5000
+
+The consumer group protocol generates additional request types. Check that
+the group coordination metrics have incremented:
+
+.. code-block:: console
+
+   $ curl -s "http://localhost:8001/stats?filter=kafka.kafka_broker" | grep -E "(find_coordinator|join_group|sync_group|leave_group)" | grep -v ": 0"
+   kafka.kafka_broker.request.find_coordinator_request: 1
+   kafka.kafka_broker.request.join_group_request: 1
+   kafka.kafka_broker.request.leave_group_request: 1
+   kafka.kafka_broker.response.find_coordinator_response: 1
+   kafka.kafka_broker.response.join_group_response: 1
+   kafka.kafka_broker.response.leave_group_response: 1
+
+
+Step 9: Test additional admin operations
+****************************************
+
+The Kafka admin client supports various topic management operations. Test
+altering topic configuration:
+
+.. code-block:: console
+
+   $ docker compose run --rm kafka-client \
+       kafka-configs --bootstrap-server proxy:10000 \
+           --alter --entity-type topics --entity-name $TOPIC \
+           --add-config retention.ms=86400000
+
+Add partitions to the topic:
+
+.. code-block:: console
+
+   $ docker compose run --rm kafka-client \
+       kafka-topics --bootstrap-server proxy:10000 \
+           --alter --topic $TOPIC --partitions 3
+
+Check the admin operation metrics:
+
+.. code-block:: console
+
+   $ curl -s "http://localhost:8001/stats?filter=kafka.kafka_broker" | grep -E "(incremental_alter_configs|create_partitions)" | grep -v ": 0"
+   kafka.kafka_broker.request.incremental_alter_configs_request: 1
+   kafka.kafka_broker.request.create_partitions_request: 1
+
+
+Step 10: Delete the topic
+*************************
+
+Clean up by deleting the test topic:
+
+.. code-block:: console
+
+   $ docker compose run --rm kafka-client \
+       kafka-topics --bootstrap-server proxy:10000 --delete --topic $TOPIC
+
+Verify the delete operation was tracked:
+
+.. code-block:: console
+
+   $ curl -s "http://localhost:8001/stats?filter=kafka.kafka_broker.request.delete_topics" | grep -v ": 0"
+   kafka.kafka_broker.request.delete_topics_request: 1
+
 .. seealso::
 
   :ref:`Envoy Kafka broker filter <config_network_filters_kafka_broker>`

kafka/verify.sh

@@ -79,3 +79,40 @@ for stat in "${EXPECTED_BROKER_STATS[@]}"; do
         "$stat" \
         "http://localhost:${PORT_ADMIN}/stats?filter=${filter}"
 done
+
+run_log "Test consumer group coordination"
+# Run a consumer in a group - it will timeout after 5s
+# The timeout is expected since there are no new messages, so we ignore the exit code
+kafka_client kafka-console-consumer --bootstrap-server proxy:10000 \
+    --topic $TOPIC --group test-group --timeout-ms 5000 || true
+
+run_log "Check consumer group metrics"
+EXPECTED_GROUP_STATS=(
+    "kafka.kafka_broker.request.find_coordinator_request"
+    "kafka.kafka_broker.request.join_group_request"
+    "kafka.kafka_broker.response.find_coordinator_response"
+    "kafka.kafka_broker.response.join_group_response")
+for stat in "${EXPECTED_GROUP_STATS[@]}"; do
+    has_metric_with_at_least_1 "${stat}"
+done
+
+run_log "Test alter topic config"
+kafka_client kafka-configs --bootstrap-server proxy:10000 \
+    --alter --entity-type topics --entity-name $TOPIC \
+    --add-config retention.ms=86400000
+
+run_log "Check incremental_alter_configs metric"
+has_metric_with_at_least_1 "kafka.kafka_broker.request.incremental_alter_configs_request"
+
+run_log "Test add partitions"
+kafka_client kafka-topics --bootstrap-server proxy:10000 \
+    --alter --topic $TOPIC --partitions 3
+
+run_log "Check create_partitions metric"
+has_metric_with_at_least_1 "kafka.kafka_broker.request.create_partitions_request"
+
+run_log "Test delete topic"
+kafka_client kafka-topics --bootstrap-server proxy:10000 --delete --topic $TOPIC
+
+run_log "Check delete_topics metric"
+has_metric_with_at_least_1 "kafka.kafka_broker.request.delete_topics_request"