Charmed Apache Kafka Operator

Overview

The Charmed Apache Kafka Operator delivers automated operations management from Day 0 to Day 2 on the Apache Kafka event streaming platform. It is an open source, end-to-end, production ready data platform on top of cloud native technologies.

The Charmed Operator can be found on Charmhub and it comes with production-ready features such as:

• Fault-tolerance, replication, scalability and high-availability out-of-the-box.
• SASL/SCRAM auth for Broker-Broker and Client-Broker authentication enabled by default.
• Access control management supported with user-provided ACL lists.

As currently Apache Kafka requires a paired Apache ZooKeeper deployment in production, this operator makes use of Charmed Apache ZooKeeper for various essential functions.

Features checklist

The following are some of the most important planned features and their implementation status:

• Super-user creation
• Inter-broker auth
• Horizontally scale brokers
• Username/Password creation for related applications
• Automatic topic creation with associated user ACLs
• Persistent storage support with Juju Storage
• TLS/SSL encrypted connections
• mTLS
• Multi-application clusters
• Partition rebalancing during broker scaling

Requirements

For production environments, it is recommended to deploy at least 5 nodes for Apache Zookeeper and 3 for Apache Kafka.

The following requirements are meant to be for production environment:

• 64GB of RAM
• 24 cores
• 12 storage devices
• 10 GbE card

The charm can be deployed in much smaller environments if needed. For more information on requirements and version compartibility, see the Requirements page.

Usage

This section demonstrates basic usage of the Charmed Apache Kafka operator. For more information on how to perform typical tasks, see the How to guides section of the Charmed Apache Kafka documentation.

Deployment

Charmed Apache Kafka and Charmed Apache ZooKeeper can both be deployed as follows:

$ juju deploy zookeeper -n 5
$ juju deploy kafka -n 3

After this, it is necessary to connect them:

$ juju relate kafka zookeeper

To watch the process, the juju status command can be used. Once all the units are shown as active|idle the credentials to access a broker can be queried with:

juju run-action kafka/leader get-admin-credentials --wait

Apache Kafka ships with bin/*.sh commands to do various administrative tasks, e.g bin/kafka-config.sh to update cluster configuration, bin/kafka-topics.sh for topic management, and many more! Charmed Apache Kafka provides these commands for administrators to run their desired cluster configurations securely with SASL authentication, either from within the cluster or as an external client.

For example, to list the current topics on the Apache Kafka cluster, run the following command:

BOOTSTRAP_SERVERS=$(juju run-action kafka/leader get-admin-credentials --wait | grep "bootstrap.servers" | cut -d "=" -f 2)
juju ssh kafka/leader 'charmed-kafka.topics --bootstrap-server $BOOTSTRAP_SERVERS --list --command-config /var/snap/charmed-kafka/common/client.properties'

Note that Charmed Apache Kafka cluster is secure-by-default: when no other application is related to Charmed Apache Kafka, listeners are disabled, thus preventing any incoming connection. However, even for running the commands above, listeners must be enabled. If there are no other applications, you can deploy a data-integrator charm and relate it to Charmed Apache Kafka to enable listeners.

Available Charmed Apache Kafka bin commands can be found with:

snap info charmed-kafka

Scaling

The charm can be scaled up using juju scale-application command:

juju scale-application kafka <num_of_units_to_scale_to>

This will add or remove brokers to match the required number. For example, to scale a deployment with 3 kafka units to 5, run:

juju scale-application kafka 5

Even when scaling multiple units at the same time, the charm uses a rolling restart sequence to make sure the cluster stays available and healthy during the operation.

Password rotation

The operator user is used internally by the Charmed Apache Kafka Operator. The set-password action can be used to rotate its password:

juju run-action kafka/leader set-password password=<password> --wait

Use the same action without a password parameter to randomly generate a password for the operator user.

Storage support

Currently, the Charmed Apache Kafka Operator supports 1 or more storage volumes. A 10G storage volume will be installed by default for log.dirs. This is used for logs storage, mounted on /var/snap/kafka/common

When storage is added or removed, the Apache Kafka service will restart to ensure it uses the new volumes. Additionally, log + charm status messages will prompt users to manually reassign partitions so that the new storage volumes are populated. By default, Apache Kafka will not assign partitions to new directories/units until existing topic partitions are assigned to it, or a new topic is created.

Relations

The Charmed Apache Kafka Operator supports Juju relations for interfaces listed below.

The kafka_client interface

The kafka_client interface is used with the Data Integrator charm, which upon relation automatically provides credentials and endpoints for connecting to the desired product.

To deploy the data-integrator charm with the desired topic-name and user roles:

juju deploy data-integrator
juju config data-integrator topic-name=test-topic extra-user-roles=producer,consumer

To relate the two applications:

juju relate data-integrator kafka

To retrieve information, enter:

juju run-action data-integrator/leader get-credentials --wait

The output looks like this:

unit-data-integrator-0:
  UnitId: data-integrator/0
  id: "4"
  results:
    kafka:
      consumer-group-prefix: relation-27-
      endpoints: 10.123.8.133:19092
      password: ejMp4SblzxkMCF0yUXjaspneflXqcyXK
      tls: disabled
      username: relation-27
      zookeeper-uris: 10.123.8.154:2181,10.123.8.181:2181,10.123.8.61:2181/kafka
    ok: "True"
  status: completed
  timing:
    completed: 2023-01-27 14:22:51 +0000 UTC
    enqueued: 2023-01-27 14:22:50 +0000 UTC
    started: 2023-01-27 14:22:51 +0000 UTC

The tls-certificates interface

The tls-certificates interface is used with the tls-certificates-operator charm.

To enable TLS, deploy the TLS charm first:

juju deploy tls-certificates-operator

Then, add the necessary configurations:

juju config tls-certificates-operator generate-self-signed-certificates="true" ca-common-name="Test CA"

And enable TLS by relating the two applications to the tls-certificates charm:

juju relate tls-certificates-operator zookeeper
juju relate tls-certificates-operator kafka

Updates to private keys for certificate signing requests (CSR) can be made via the set-tls-private-key action:

# Updates can be done with auto-generated keys with
juju run-action kafka/0 set-tls-private-key --wait
juju run-action kafka/1 set-tls-private-key --wait
juju run-action kafka/2 set-tls-private-key --wait

Now you can generate shared internal key:

openssl genrsa -out internal-key.pem 3072

Passing keys to external/internal keys should only be done with base64 -w0 not cat.

Apply keys on each Charmed Apache Kafka unit:

juju run-action kafka/0 set-tls-private-key "internal-key=$(base64 -w0 internal-key.pem)"  --wait
juju run-action kafka/1 set-tls-private-key "internal-key=$(base64 -w0 internal-key.pem)"  --wait
juju run-action kafka/2 set-tls-private-key "internal-key=$(base64 -w0 internal-key.pem)"  --wait

To disable TLS remove the relation:

juju remove-relation kafka tls-certificates-operator
juju remove-relation zookeeper tls-certificates-operator

Note: The TLS settings here are for self-signed-certificates which are not recommended for production clusters, the tls-certificates-operator charm offers a variety of configurations, read more on the TLS charm in the documentation.

Monitoring

The Charmed Apache Kafka Operator comes with the JMX exporter. The metrics can be queried by accessing the http://<unit-ip>:9101/metrics endpoints.

Additionally, the charm provides integration with the Canonical Observability Stack.

Deploy the cos-lite bundle in a Kubernetes environment. This can be done by following the deployment tutorial. Since the Charmed Apache Kafka Operator is deployed on a machine environment, it is needed to offer the endpoints of the COS relations. The offers-overlay can be used, and this step is shown in the COS tutorial.

Next, deploy grafana-agent and follow the tutorial to relate it to the COS Lite offers.

Now, relate kafka with the grafana-agent:

juju relate kafka grafana-agent

After this is complete, Grafana will show two new dashboards: Kafka Metrics and Node Exporter Kafka.

Security

For an overview of security features of the Charmed Apache Kafka Operator, see the Security page in the Explanation section of the documentation.

Security issues in the Charmed Apache Kafka Operator can be reported through LaunchPad. Please do not file GitHub issues about security issues.

Performance tuning

For information on tuning performance of Charmed Apache Kafka, see the Performance tuning reference page.

Contributing

Please see the Juju SDK docs for guidelines on enhancements to this charm following best practice guidelines, and CONTRIBUTING.md for developer guidance.

Also, if you truly enjoy working on open-source projects like this one, check out the career options we have at Canonical.

License

Charmed Apache Kafka is free software, distributed under the Apache Software License, version 2.0. See LICENSE for more information.