[Bug]: Include default capacity for cruise control

[azexs]

Bug Description

When I create a kafka cluster with cruisecontrol, the operator creates a configmap with capacity settings for specific brokers managed by strimzi. When connecting an external broker to a strimzi cluster, the capacity for that broker is not in the configmap and cruisecontrol fails because of a null pointer. Default value for brokers should be defined with id “-1” according to cruise control. Would it be correct to extend the capacity.json file with an additional entry with id “-1” with default capacity brokers?

I am testing a specific case of connecting an external cluster to a strimzi cluster to replicate data using cruisecontrol.

Steps to reproduce

1. Create strimzi kafka cluster with 2 brokers and strimzi
2. Deploy external apache kafka broker and configure it to connect to strimzi cluster.
3. Run cruisecontrol.

Expected behavior

capacity.json should include default capacity with id "-1"

https://github.com/linkedin/cruise-control/wiki/Configurations#populating-the-capacity-config-file

Strimzi version

0.45.0

Kubernetes version

1.29.2

Installation method

No response

Infrastructure

No response

Configuration files and logs

2025-03-02 20:54:58 ERROR GoalOptimizer:615 - Proposal precomputation encountered error
com.linkedin.kafka.cruisecontrol.exception.BrokerCapacityResolutionException: Unable to resolve capacity of broker 3. Either (1) adding the default broker capacity (via adding capacity for broker -1 and allowing capacity estimation) or (2) adding missing broker's capacity in file /opt/cruise-control/custom-config/capacity.json.
at com.linkedin.kafka.cruisecontrol.config.BrokerCapacityConfigFileResolver.capacityForBroker(BrokerCapacityConfigFileResolver.java:181) ~[cruise-control-2.5.138.jar:?]
at com.linkedin.kafka.cruisecontrol.monitor.LoadMonitor.populateClusterCapacity(LoadMonitor.java:586) ~[cruise-control-2.5.138.jar:?]
at com.linkedin.kafka.cruisecontrol.monitor.LoadMonitor.clusterModel(LoadMonitor.java:516) ~[cruise-control-2.5.138.jar:?]
at com.linkedin.kafka.cruisecontrol.monitor.LoadMonitor.clusterModel(LoadMonitor.java:472) ~[cruise-control-2.5.138.jar:?]
at com.linkedin.kafka.cruisecontrol.monitor.LoadMonitor.clusterModel(LoadMonitor.java:442) ~[cruise-control-2.5.138.jar:?]
at com.linkedin.kafka.cruisecontrol.analyzer.GoalOptimizer$ProposalCandidateComputer.run(GoalOptimizer.java:603) ~[cruise-control-2.5.138.jar:?]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:539) ~[?:?]
at java.util.concurrent.FutureTask.run(FutureTask.java:264) ~[?:?]
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:304) ~[?:?]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136) ~[?:?]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635) ~[?:?]
at java.lang.Thread.run(Thread.java:840) ~[?:?]

Additional context

No response

[im-konge]

Triaged on 6.3.2025: Based on I am testing a specific case of connecting an external cluster to a strimzi cluster to replicate data using cruisecontrol. it seems that you are doing something that is completely unsupported, as Strimzi doesn't have any control of the external cluster.

@azexs what are you trying to achieve with this?