How to change the number of replicas of a Kafka topic?

Question

After a Kafka topic has been created by a producer or an administrator, how would you change the number of replicas of this topic?

Answer 1

1. Copy all topics to json file

#!/bin/bash
topics=`kafka-topics.sh --zookeeper localhost:2181 --list`

while read -r line; do lines+=("$line"); done <<<"$topics"
echo '{"version":1,
 "topics":['
 for t in $topics; do
     echo -e '     { "topic":' \"$t\" '},'
done

echo '  ]
}'

bash alltopics.sh > alltopics.json

2. Run kafka-reassign-partitions.sh to generate rebalanced file

kafka-reassign-partitions.sh --zookeeper localhost:2181 --broker-list "0,1,2" --generate --topics-to-move-json-file alltopics.json > reassign.json

3. Cleanup reassign.json file it contains existing and proposed values

4. Run kafka-reassign-partitions.sh to rebalance topics

kafka-reassign-partitions.sh --zookeeper localhost:2181 --reassignment-json-file reassign.json --execute