Chapter 16. Using Cruise Control to modify topic replication factor

Make requests to the /topic_configuration endpoint of the Cruise Control REST API to modify topic configurations, including the replication factor.

Prerequisites

Procedure

Start the Cruise Control server. The server starts on port 9092 by default; optionally, specify a different port.
```
cd ./cruise-control/
./kafka-cruise-control-start.sh config/cruisecontrol.properties <port_number>
```
To verify that Cruise Control is running, send a GET request to the /state endpoint of the Cruise Control server:
```
curl -X GET 'http://<cc_host>:<cc_port>/kafkacruisecontrol/state'
```
Run the bin/kafka-topics.sh command with the --describe option to check the current replication factor of the target topic:
```
./bin/kafka-topics.sh \
  --bootstrap-server localhost:9092 \
  --topic <topic_name> \
  --describe
```
Update the replication factor for the topic:
```
curl -X POST 'http://<cc_host>:<cc_port>/kafkacruisecontrol/topic_configuration?topic=<topic_name>&replication_factor=<new_replication_factor>&dryrun=false'
```
For example, curl -X POST 'localhost:9090/kafkacruisecontrol/topic_configuration?topic=topic1&replication_factor=3&dryrun=false'.
Run the bin/kafka-topics.sh command with the --describe option, as before, to see the results of the change to the topic.