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// assembly-cruise-control-concepts.adoc

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[id='con-cruise-control-overview-{context}']
= Cruise Control components and features

[role="_abstract"]
Cruise Control consists of four main components--the Load Monitor, the Analyzer, the Anomaly Detector, and the Executor--and a REST API for client interactions.
Strimzi utilizes the REST API to support the following Cruise Control features:
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* Generating optimization proposals from optimization goals.
* Rebalancing a Kafka cluster based on an optimization proposal. 
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Optimization goals:: An optimization goal describes a specific objective to achieve from a rebalance. 
For example, a goal might be to distribute topic replicas across brokers more evenly. 
You can change what goals to include through configuration.
A goal is defined as a hard goal or soft goal.
You can add hard goals through Cruise Control deployment configuration.
You also have main, default, and user-provided goals that fit into each of these categories.  
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* *Hard goals* are preset and must be satisfied for an optimization proposal to be successful.
* *Soft goals* do not need to be satisfied for an optimization proposal to be successful. 
They can be set aside if it means that all hard goals are met.  
* *Main goals* are inherited from Cruise Control. Some are preset as hard goals.
Main goals are used in optimization proposals by default.  
* *Default goals* are the same as the main goals by default. 
You can specify your own set of default goals.  
* *User-provided goals* are a subset of default goals that are configured for generating a specific optimization proposal. 
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Optimization proposals::  Optimization proposals comprise the goals you want to achieve from a rebalance. 
You generate an optimization proposal to create a summary of proposed changes and the results that are possible with the rebalance.
The goals are assessed in a specific order of priority.
You can then choose to approve or reject the proposal.
You can reject the proposal to run it again with an adjusted set of goals.  
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You can generate an optimization proposal in one of three modes.
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* *`full`* is the default mode and runs a full rebalance.
* *`add-brokers`* is the mode you use after adding brokers when scaling up a Kafka cluster.  
* *`remove-brokers`* is the mode you use before removing brokers when scaling down a Kafka cluster.
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Other Cruise Control features are not currently supported, including self healing, notifications, write-your-own goals, and changing the topic replication factor.

[role="_additional-resources"]
.Additional resources

* {CruiseControlConfigDocs}
