Kafka reassignment of __consumer_offsets incorrect?

Question

I am confused with how kafka-reassignment-paritions works for __consumer_offsets topic?

I start with 1 zk and 1 kafka broker, create a test topic with replication=1, par

Answer 1

If you want to increase the replication factor for a topic, follow steps below:

1. Create a json file containing the reassignment plan. In your case, the file might look like:

   {"version":1, "partitions":[
     {"topic":"__consumer_offsets","partition":0,"replicas":[101,102]}, 
     {"topic":"__consumer_offsets","partition":1,"replicas":[102,101]},
     {"topic":"__consumer_offsets","partition":2,"replicas":[101,102]},
     {"topic":"__consumer_offsets","partition":3,"replicas":[102,101]},
     ...
     {"topic":"__consumer_offsets","partition":49,"replicas":[101,102]}
   ]}
   

2. Run command below to increase RF for this internal topic:

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

Then run kafka-topics.sh --describe to see if replication factor is bumped up to 2.

Answer 2

You can use the reassignment tool to generate json for your own advantage. In your topics-to-move.json, instead of putting partition values, put {"version":1, "topics":[{"topic":"__consumer_offsets"}]}

Now when you run kafka-reassign-partitions --zookeeper zookeeper1:2181 --topics-to-move-json-file topics-to-move.json --broker-list "101,102" --generate You will get recommended partition assignment from tool.

Save that file as reassignment-proposed.json and store old assignment into rollback.json.

Use that file to start reassignment /kafka-reassign-partitions.sh --zookeeper localhost:2181 --reassignment-json-file reassignment-proposed.json --execute Verify assignment using --verify option