Connecting KafkaTopics of multiple namespaces to a single Kafka cluster

[osamamagdy]

Hello,
I have a use case where I deploy the kafka cluster in one namesapce (for example namespace1) but all our KafkaTopics will be deployed in multiple namespaces for separation between different teams where each team deploy its own KafkaTopic in a separate namespace. In the documentation, it mentions here that we can set the Cluster operator to watch all namespaces, I only have one kafka cluster but multiple kafka topics, will that be enough?
What is the use of TopicOperator in this scenario?

[scholzj]

The Topic and User Operators always watch only one namespace. So you cannot use it for the scenario you describe. You would need to copy the KafkaTopics into a single namespace for example to make a use of it.

[osamamagdy]

@ppatierno Thanks for stepping in. So, the Topic operators must be in the same namespace as the kafka cluster itself?

[ppatierno]

Not sure what you mean by "must be". When you create a Kafka custom resource within the namespace foo and you have the topic operator "enabled" in the YAML like:

...
entityOperator:
  topicOperator: {}
  userOperator: {}

Then the Strimzi cluster operator will deploy the Kafka cluster in the namespace foo as well as the Topic and User operator (within the entity operator pod) in the same namespace foo.
It's not something you can change.

[osamamagdy]

I mean can I create a topic operator named bar-topic-operator and deploy that operator in namespace bar then in the Kafka cluster (created in foo namespace) , I list this inside

entityOperator:
  topicOperator: { bar-topic-operator }
  userOperator: {}

If this works, I will be able to add KafkaTopics to the bar namespace

[ppatierno]

I mean can I create a topic operator named bar-topic-operator and deploy that operator in namespace bar then in the Kafka cluster (created in foo namespace) , I list this inside.

No you can't. You don't deploy the topic operator by yourself. It's part of the Kafka cluster deployment by the Cluster operator.

I am not sure where I was not clear tbh :-)
The topic operator is per namespace. It's deployed by the cluster operator for you alongside the Kafka cluster.
For example, you have a Kafka custom resource named my-cluster-1 and you deploy it into foo namespace? You will get a Kafka cluster running in foo together with a Topic Operator running in foo and watching topics inside foo.
Then you create a Kafka custom resource named my-cluster-2 and you deploy it into bar namespace? You will get a Kafka cluster running in bar together with a Topic Operator running in bar and watching topics inside bar.
So 2 Kafka clusters in 2 different namespaces, and each one with its own Topic Operator.

[osamamagdy]

Thanks, so there is no workaround to have one single Kafka cluster managing multiple topics in multiple namespaces?