Why does strimzi-operator add PreferredLeaderElectionGoal (PLE) to goals?

[avoidik]

Hello,

The question is quite simple, but there's no rationale behind it. Why?

[avoidik]

If you'd check in the CC source-code, there's not PLE in the default.goals: https://github.com/linkedin/cruise-control/blob/3.0.3/cruise-control/src/main/java/com/linkedin/kafka/cruisecontrol/config/constants/AnalyzerConfig.java#L311-L327

However, strimzi-operator adds it here: https://github.com/strimzi/strimzi-kafka-operator/blob/0.50.1/cluster-operator/src/main/java/io/strimzi/operator/cluster/model/cruisecontrol/CruiseControlConfiguration.java#L53

As a result, the PLE is getting executed with every rebalancing.

[avoidik]

What's the theoretical impact? During the rebalancing the PLE may have impact to a few other goals, it also creates a skew by prioritising the first broker from the list.

https://github.com/linkedin/cruise-control/blob/3.0.3/cruise-control/src/main/java/com/linkedin/kafka/cruisecontrol/analyzer/goals/PreferredLeaderElectionGoal.java#L136-L139

[scholzj]

@kyguy @ppatierno Do you remember by any chance why this is included?

[ppatierno]

Looking at the code it was added as default goal since the beginning, If I saw it correctly since 2020. I can't see any specific reason why it was added if on purpose or not. I can totally understand the reasoning and its impact. @kyguy wdyt?