Apache Kafka - K8s

This is part of the Charmed Kafka K8s Tutorial. Please refer to this page for more information and the overview of the content.

Transport Layer Security (TLS)

TLS is used to encrypt data exchanged between two applications; it secures data transmitted over the network. Typically, enabling TLS within a highly available database, and between a highly available database and client/server applications, requires domain-specific knowledge and a high level of expertise. Fortunately, the domain-specific knowledge has been encoded into Charmed Kafka. This means (re-)configuring TLS on Charmed Kafka is readily available and requires minimal effort on your end.

Again, relations come in handy here as TLS is enabled via relations; i.e. by relating Charmed Kafka to the Self-signed Certificates Charm via the tls-certificates charm relations. The tls-certificates relation centralises TLS certificate management in a consistent manner and handles providing, requesting, and renewing TLS certificates, making it possible to use different providers, like the self-signed certificates but also other services, e.g. Let’s Encrypt.

Note: In this tutorial, we will distribute self-signed certificates to all charms (Kafka, ZooKeeper and client applications) that are signed using a root self-signed CA that is also trusted by all applications. This setup is only for show-casing purposes and self-signed certificates should never be used in a production cluster. For more information about which charm may better suit your use-case, please refer to this post.

Configure TLS

Before enabling TLS on Charmed Kafka we must first deploy the self-signed-certificates charm:

juju deploy self-signed-certificates --config ca-common-name="Tutorial CA"

Wait for the charm settles into an active/idle state, as shown by the juju status

Model     Controller  Cloud/Region        Version  SLA          Timestamp
tutorial  microk8s    microk8s/localhost  3.1.5    unsupported  21:32:35+02:00

App                        Version  Status  Scale  Charm                      Channel    Rev  Exposed  Message
...
self-signed-certificates            active      1  self-signed-certificates   stable     72   no       
...

Unit                          Workload  Agent  Address    Ports  Message
...
self-signed-certificates/0*   active    idle   10.1.36.91        
...

To enable TLS on Charmed Kafka K8s, relate the both the kafka-k8s and zookeeper-k8s charms with the self-signed-certificates charm:

juju relate zookeeper-k8s self-signed-certificates
juju relate kafka-k8s:certificates self-signed-certificates

After the charms settle into active/idle states, the Kafka listeners should now have been swapped to the default encrypted port 9093. This can be tested by testing whether the ports are open/closed with telnet

telnet <IP> 9092 
telnet <IP> 9093

Enable TLS encrypted connection

Once the Kafka cluster is enabled to use encrypted connection, client applications should be configured as well to connect to the correct port as well as trust the self-signed CA provided by the self-signed-certificates charm.

Make sure that the kafka-test-app is not connected to the Kafka charm, by removing the relation if it exists

juju remove-relation kafka-test-app kafka-k8s

Then enable encryption on the kafka-test-app by relating with the self-signed-certificates charm

juju relate kafka-test-app  self-signed-certificates

We can then set up the kafka-test-app to produce messages with the usual configuration (note that there is no difference here with the unencrypted workflow)

juju config kafka-test-app topic_name=test_encryption_topic role=producer num_messages=25

and then relate with the kafka-k8s cluster

juju relate kafka-k8s kafka-test-app

As before, you can check that the messages are pushed into the Kafka cluster by inspecting the logs

juju exec --application kafka-test-app "tail /tmp/*.log"

Note that if the kafka-test-app was running before, there may be multiple logs related to the different runs. Refer to the latest logs produced and also check that in the logs the connection is indeed established with the encrypted port 9093.

Remove external TLS certificate

To remove the external TLS and return to the locally generate one, un-relate applications:

juju remove-relation kafka-k8s  self-signed-certificates
juju remove-relation zookeeper-k8s  self-signed-certificates

The Charmed Kafka K8s application is not using TLS anymore.