Hi, I have a Kraft cluster running Kafka 3.5 and using the metadata.version 3.5 as well:
$ bin/kafka-features.sh --bootstrap-server localhost:9092 describe Feature: metadata.version SupportedMinVersion: 3.0-IV1 SupportedMaxVersion: 3.5-IV2 FinalizedVersionLevel: 3.5-IV2 Epoch: 140 The upgrade docs <https://kafka.apache.org/documentation/#upgrade_350_kraft> suggest that I should be able to downgrade the metadata version as long as it is not to 3.0-3.2 versions. However, whatever version I try to downgrade it to and whether it is safe or unsafe downgrade, it always seems to fail: $ ./bin/kafka-features.sh --bootstrap-server localhost:9092 downgrade --metadata 3.4 Could not downgrade metadata.version to 8. Invalid metadata.version 8. Refusing to perform the requested downgrade because it might delete metadata information. Retry using UNSAFE_DOWNGRADE if you want to force the downgrade to proceed. 1 out of 1 operation(s) failed. $ ./bin/kafka-features.sh --bootstrap-server localhost:9092 downgrade --metadata 3.4 --unsafe Could not downgrade metadata.version to 8. Invalid metadata.version 8. Unsafe metadata downgrade is not supported in this version. 1 out of 1 operation(s) failed. And it does not really matter whether I try to downgrade to 3.4, 3.4-IV0, 3.5-IV1. In the logs, I see the following INFO message while running the downgrade command: 2023-10-01 20:59:59,910 INFO Unable to get feature level information for controller(s): 4, 5 (org.apache.kafka.controller.QuorumFeatures) [quorum-controller-3-event-handler] Not sure if that is related. The cluster seems to work fine apart from the metadata downgrade. (The cluster I was trying it on has 3 controllers with node IDs 3, 4, and 5) Anyone has an idea what I'm doing wrong? Or is this something that is not supported? Or some bug? Thanks & Regards Jakub
