Could someone please help answer this question? I would really appreciate it—thank you!
Jianbin Chen <[email protected]> 于2026年1月28日周三 16:19写道： > > > ---------- Forwarded message --------- > 发件人： Jianbin Chen <[email protected]> > Date: 2026年1月28日周三 09:49 > Subject: Inquiry about migrating from ZooKeeper to KRaft > To: <[email protected]> > > > Hi everyone, > > I’m trying to migrate a test cluster from ZooKeeper to KRaft in-place > (i.e., not provisioning three new controller-only nodes first and then > pointing the existing brokers to them). I hit a problem and would > appreciate any pointers. > > What I did > - Enabled zookeeper.metadata.migration.enable on each existing broker and > set the controller quorum settings so each broker acts as a > controller+broker (process.roles=broker,controller). > - Rolled the three nodes. > > Relevant broker configuration (each broker has similar config; example > shown): > > ``` > process.roles=broker,controller > node.id=7 > broker.id=7 > zookeeper.metadata.migration.enable=true > controller.quorum.voters=7@broker1:9093,6@broker2:9093,4@broker3:9093 > controller.quorum.bootstrap.servers=broker1:9093,broker2:9093,broker3:9093 > zookeeper.connect=zk1:2181,zk2:2181,zk3:2181 > controller.listener.names=CONTROLLER > group.initial.rebalance.delay.ms=0 > listeners=SSL://ip:9092,PLAINTEXT://ip:9192,CONTROLLER://ip:9093 > > listener.security.protocol.map=SSL:SSL,PLAINTEXT:PLAINTEXT,CONTROLLER:PLAINTEXT > ``` > > Observed behavior > After rolling restart, the controller logs show the quorum is ready for > migration, but the controller repeatedly logs that no brokers are known to > KRaft: > > ``` > [2026-01-27 17:47:15,626] INFO [KRaftMigrationDriver id=7] Controller > Quorum is ready for Zk to KRaft migration. Now waiting for ZK brokers. > (org.apache.kafka.metadata.migration.KRaftMigrationDriver) > [2026-01-27 17:47:15,627] INFO [KRaftMigrationDriver id=7] 7 transitioning > from WAIT_FOR_CONTROLLER_QUORUM to WAIT_FOR_BROKERS state > (org.apache.kafka.metadata.migration.KRaftMigrationDriver) > [2026-01-27 17:47:15,627] INFO [KRaftMigrationDriver id=7] No brokers are > known to KRaft, waiting for brokers to register. > (org.apache.kafka.metadata.migration.KRaftMigrationDriver) > [2026-01-27 17:47:15,726] INFO [KRaftMigrationDriver id=7] No brokers are > known to KRaft, waiting for brokers to register. > (org.apache.kafka.metadata.migration.KRaftMigrationDriver) > [2026-01-27 17:47:15,925] INFO [KRaftMigrationDriver id=7] No brokers are > known to KRaft, waiting for brokers to register. > ``` > It appears that the controller quorum becomes ready for migration, but the > migration driver repeatedly logs "No brokers are known to KRaft, waiting > for brokers to register." and does not make progress. > > My current understanding is as follows: > - Migration from ZooKeeper to KRaft normally involves standing up a > separate controller-only KRaft cluster first, then updating the existing > brokers to point to that controller cluster (via > controller.quorum.bootstrap.servers) and enabling > zookeeper.metadata.migration.enable. > - Performing an in-place migration (having the existing brokers also act > as controllers) seems risky because controller quorum elections require a > majority of controller nodes. For example, with topics having > replication.factor=2, you may need to restart two brokers to form the new > controller quorum, which would make RF=2 topics unavailable during the > migration. > - Therefore I am unsure whether my understanding is correct (i.e., > in-place migration is unsafe or unsupported for production-like setups) or > whether Kafka actually supports in-place migration and I have a > configuration error. > > I would greatly appreciate it if you could confirm which is the case. If > in-place migration is supported, could you please advise what configuration > or sequence I am missing so that brokers register with KRaft correctly? If > in-place migration is not recommended, could you recommend the safest > procedure to migrate a test cluster while minimizing downtime for producers > and consumers? > > Thank you very much for your time and assistance. > > Best regards, > Jianbin Chen >
