How to manage related applications
Relations to new applications are supported via the “kafka_client” interface.
Within Juju via kafka_client interface
If the charm supports the kafka_client interface, just create a relation between the two charms:
juju relate kafka application
To remove a relation:
juju remove-relation kafka application
Outside Juju or for charms not implementing kafka_client
The kafka_client interface is used with the data-integrator charm. This charm automatically creates and manages product credentials needed to authenticate with different kinds of data platform charmed products:
Deploy the Data Integrator charm with the desired topic-name and user roles:
juju deploy data-integrator --channel edge
juju config data-integrator topic-name=test-topic extra-user-roles=producer,consumer
Relate the two applications with:
juju relate data-integrator kafka
To retrieve information, enter:
juju run data-integrator/leader get-credentials
This should output something like:
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"
Password rotation
Password rotation can be performed in multiple ways, depending on the requirements.
External clients
There are two ways to rotate credentials of an external client. One is simply to delete and re-create the relation, the other one can be performed without any downtime.
With client application downtime
The easiest way to rotate user credentials of client applications is by removing and then re-relating
the application (either a charm supporting the kafka-client interface or a data-integrator) with the kafka charm:
juju remove-relation kafka <charm-or-data-integrator>
# wait for the relation to be torn down
juju relate kafka <charm-or-data-integrator>
The successful credential rotation can be confirmed by retrieving the new password with the action get-credentials.
Without client application downtime
In some use-cases credentials should be rotated with no or limited application downtime. If credentials should be rotated with no or limited downtime, you can deploy a new charm with the same permissions and resource definition, for example:
juju deploy data-integrator rotated-user --channel stable \
--config topic-name=test-topic --config extra-user-roles=admin
The data-integrator charm can then be related to the kafka charm to create a new user:
juju relate kafka rotated-user
At this point, we effectively have two overlapping users, so that applications can swap the password from one to another. If the applications consist of fleets of independent producers and consumers, user credentials can be rotated progressively across fleets, such that no effective downtime is achieved.
Once all applications have rotated their credentials, it is then safe to remove data first data-integrator charm
juju remove-application data-integrator
Internal 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.
# to set a specific password for the operator user
juju run kafka/leader set-password password=<password>
# to randomly generate a password for the operator user
juju run kafka/leader set-password