Preferred replica election is naive. It will always follow the order of the
replicas as they are set. So if you want to set the default leader, just
make it the first replica in the list for the partition. We build the JASON
this way all the time.
-Todd
On Dec 22, 2017 6:46 AM, "Sagar" <sagarmeansoc...@gmail.com> wrote:
Hi,
Had a question on Kafka reassign partitions tool.
We have a 3 node cluster but our replication factor is set to 1. So we have
been looking to increase it to 3 for HA.
I tried the tool on a couple of topics and it increases the replication
factor alright. Also it doesn't change the leader as the leader still is in
the RAR.
This is how I run it:
Json which is used:
{"version":1,"partitions":[
{"topic":"cric-engine.engine.eng_fow","partition":3,"
replicas":[92,51,101]}]}
Earlier config for the topic
kafka-topics --describe --topic cric-engine.engine.eng_fow --zookeeper
10.0.4.165:2181,10.0.5.139:2181,10.0.6.106:2181
Topic:cric-engine.engine.eng_fow PartitionCount:5 ReplicationFactor:3
Configs:
Topic: cric-engine.engine.eng_fow Partition: 0 Leader: 101 Replicas:
92,51,101 Isr: 101,51,92
Topic: cric-engine.engine.eng_fow Partition: 1 Leader: 51 Replicas:
92,51,101 Isr: 51,101,92
Topic: cric-engine.engine.eng_fow Partition: 2 Leader: 92 Replicas: 92 Isr:
92
Topic: cric-engine.engine.eng_fow Partition: 3 Leader: 101 Replicas: 101
Isr:
101
Topic: cric-engine.engine.eng_fow Partition: 4 Leader: 51 Replicas: 51 Isr:
51
After running:
kafka-reassign-partitions --reassignment-json-file
increase-replication-factor.json --execute --zookeeper 10.0.4.165:2181,
10.0.5.139:2181,10.0.6.106:2181
partitions 3 Replicas increase:
kafka-topics --describe --topic cric-engine.engine.eng_fow --zookeeper
10.0.4.165:2181,10.0.5.139:2181,10.0.6.106:2181
Topic:cric-engine.engine.eng_fow PartitionCount:5 ReplicationFactor:3
Configs:
Topic: cric-engine.engine.eng_fow Partition: 0 Leader: 101 Replicas:
92,51,101 Isr: 101,51,92
Topic: cric-engine.engine.eng_fow Partition: 1 Leader: 51 Replicas:
92,51,101 Isr: 51,101,92
Topic: cric-engine.engine.eng_fow Partition: 2 Leader: 92 Replicas: 92 Isr:
92
Topic: cric-engine.engine.eng_fow Partition: 3 Leader: 101 Replicas:
92,51,101 Isr: 101,51,92
Topic: cric-engine.engine.eng_fow Partition: 4 Leader: 51 Replicas: 51 Isr:
51
What I wanted to know is that does it affect the preferred replica? If you
see the Replicas, all of them are now 92,51,101 even though the leader has
remained the same from before. So, if any of the broker goes down or we
run kafka-preferred-replica-election.sh, wouldn't it move all the leaders
to broker 92? Is my assesment correct?
If yes, then is there a way I can still do this operation by getting leader
for a partition first, then adding it to the replica list and then building
the json dynamically?
Thanks!
Sagar.
