This is part of the Charmed Kafka 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 to settle into an active/idle state, as shown by the juju status
Model Controller Cloud/Region Version SLA Timestamp
tutorial overlord localhost/localhost 3.1.6 unsupported 10:20:59Z
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, relate the both the kafka and zookeeper charms with the
self-signed-certificates charm:
juju relate zookeeper self-signed-certificates
juju relate kafka: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
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 cluster
juju relate kafka 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 self-signed-certificates
juju remove-relation zookeeper self-signed-certificates
The Charmed Kafka application is not using TLS anymore.