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José Armando García Sancio commented on KAFKA-18856: ---------------------------------------------------- Yes, a 3.9 node (broker or controller) cannot join Kafka cluster which has 4.0 as the finalized metadata version. Which node is logging this error? The 3.9 broker? {code:java} [2025-02-25 01:05:06,530] ERROR Encountered metadata loading fault: Unhandled error initializing new publishers (org.apache.kafka.server.fault.LoggingFaultHandler) org.apache.kafka.image.writer.UnwritableMetadataException: Metadata has been lost because the following could not be represented in metadata.version 3.0-IV1: feature flag(s): group.version, transaction.version {code} I would have assumed that the broker would have failed to register to the Kafka cluster because it doesn't support the 4.0 metadata version? Do you see such registration errors? It is possible that the issue is that the 3.9 broker is fetching and applying metadata records from the active controller even though it is not able to register to the cluster. Having said that, it is a confusing error message: "following could not be represented in metadata.version 3.0-IV1: feature flag(s): group.version, transaction.version." What do you think [~cmccabe] ? > 3.9 broker unable to join dynamic quorum with 4.0 controller > ------------------------------------------------------------ > > Key: KAFKA-18856 > URL: https://issues.apache.org/jira/browse/KAFKA-18856 > Project: Kafka > Issue Type: Bug > Reporter: TengYao Chi > Assignee: TengYao Chi > Priority: Major > > Test step: > * format 4.0 controller /w controller.properties & standalone > ** bin/kafka-storage.sh format --standalone -t "dAtBluZORiuJEKV2uSWB2Q" -c > config/controller.properties > * start 4.0 controller > * init 3.9 broker /w kraft/broker.properties & no-initial-controllers > ** bin/kafka-storage.sh format -t "dAtBluZORiuJEKV2uSWB2Q" --config > config/kraft/broker.properties -N > * start 3.9 broker > error message: > {code:java} > [2025-02-24 23:13:21,271] ERROR Encountered metadata loading fault: Unhandled > error initializing new publishers > (org.apache.kafka.server.fault.LoggingFaultHandler) > org.apache.kafka.image.writer.UnwritableMetadataException: Metadata has been > lost because the following could not be represented in metadata.version > 3.0-IV1: feature flag(s): group.version, transaction.version > at > org.apache.kafka.image.writer.ImageWriterOptions.handleLoss(ImageWriterOptions.java:94) > at > org.apache.kafka.image.FeaturesImage.handleFeatureLevelNotSupported(FeaturesImage.java:108) > at org.apache.kafka.image.FeaturesImage.write(FeaturesImage.java:88) > at org.apache.kafka.image.MetadataImage.write(MetadataImage.java:153) > at > org.apache.kafka.image.loader.MetadataLoader.initializeNewPublishers(MetadataLoader.java:296) > at > org.apache.kafka.image.loader.MetadataLoader.lambda$scheduleInitializeNewPublishers$0(MetadataLoader.java:267) > at > org.apache.kafka.queue.KafkaEventQueue$EventContext.run(KafkaEventQueue.java:132) > at > org.apache.kafka.queue.KafkaEventQueue$EventHandler.handleEvents(KafkaEventQueue.java:215) > at > org.apache.kafka.queue.KafkaEventQueue$EventHandler.run(KafkaEventQueue.java:186) > at java.base/java.lang.Thread.run(Thread.java:1583) > ^C[2025-02-24 23:13:21,658] INFO Terminating process due to signal SIGINT > (org.apache.kafka.common.utils.LoggingSignalHandler) > [2025-02-24 23:13:21,660] INFO App info kafka.server for 2 unregistered > (org.apache.kafka.common.utils.AppInfoParser) {code} -- This message was sent by Atlassian Jira (v8.20.10#820010)