Kafka broker

This example demonstrates some basic operations with a Kafka broker proxied through Envoy.

For your convenience, the composition provides a dockerized Kafka client.

If you have the kafka-console-* binaries installed on your host system, you can instead follow the examples using the host binary with --bootstrap-server localhost:10000.

Statistics collected by Envoy for the Kafka broker extension and related cluster metrics are also demonstrated.

Step 1: Start all of our containers

Change to the examples/kafka directory.

$ pwd
envoy/examples/kafka
$ docker compose pull
$ docker compose up --build -d
$ docker compose ps

         Name                      Command                State                            Ports
-----------------------------------------------------------------------------------------------------------------------
kafka_kafka-server_1   /etc/confluent/docker/run      Up             9092/tcp
kafka_proxy_1          /docker-entrypoint.sh /usr ... Up             0.0.0.0:10000->10000/tcp, 0.0.0.0:8001->8001/tcp
kafka_zookeeper_1      /etc/confluent/docker/run      Up (healthy)   2181/tcp, 2888/tcp, 3888/tcp

Step 2: Create a Kafka topic

Start by creating a Kafka topic with the name envoy-kafka-broker:

$ export TOPIC="envoy-kafka-broker"
$ docker compose run --rm kafka-client kafka-topics --bootstrap-server proxy:10000 --create --topic $TOPIC

Step 3: Check the Kafka topic

You can view the topics that Kafka is aware of with the kafka-topics --list argument.

Check that the topic you created exists:

$ docker compose run --rm kafka-client kafka-topics --bootstrap-server proxy:10000 --list | grep $TOPIC

Step 4: Send a message using the Kafka producer

Next, send a message for the topic you have created using the kafka-console-producer:

$ export MESSAGE="Welcome to Envoy and Kafka broker filter!"
$ docker compose run --rm kafka-client /bin/bash -c " \
    echo $MESSAGE \
    | kafka-console-producer --request-required-acks 1 --broker-list proxy:10000 --topic $TOPIC"

Step 5: Receive a message using the Kafka consumer

Now you can receive the message using the kafka-console-consumer :

$ docker compose run --rm kafka-client kafka-console-consumer --bootstrap-server proxy:10000 --topic $TOPIC --from-beginning --max-messages 1 | grep "$MESSAGE"

Step 6: Check admin `kafka_broker` stats

When you proxy to the Kafka broker, Envoy records various stats.

You can check the broker stats by querying the Envoy admin interface (the numbers might differ a little as the kafka-client does not expose precise control over its network traffic):

$ curl -s "http://localhost:8001/stats?filter=kafka.kafka_broker" | grep -v ": 0" | grep "_request:"
kafka.kafka_broker.request.api_versions_request: 9
kafka.kafka_broker.request.create_topics_request: 1
kafka.kafka_broker.request.fetch_request: 2
kafka.kafka_broker.request.find_coordinator_request: 8
kafka.kafka_broker.request.join_group_request: 2
kafka.kafka_broker.request.leave_group_request: 1
kafka.kafka_broker.request.list_offsets_request: 1
kafka.kafka_broker.request.metadata_request: 12
kafka.kafka_broker.request.offset_fetch_request: 1
kafka.kafka_broker.request.produce_request: 1
kafka.kafka_broker.request.sync_group_request: 1

Step 7: Check admin `kafka_service` cluster stats

Envoy also records cluster stats for the Kafka service:

$ curl -s "http://localhost:8001/stats?filter=cluster.kafka_service" | grep -v ": 0"
cluster.kafka_service.max_host_weight: 1
cluster.kafka_service.membership_healthy: 1
cluster.kafka_service.membership_total: 1