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  1. Kafka
  2. KAFKA-4298

LogCleaner writes inconsistent compressed message set if topic message format != message format



    • Bug
    • Status: Resolved
    • Critical
    • Resolution: Fixed
    • None
    • None


      When cleaning the log, we don't want to convert messages to the format configured for the topic due to KAFKA-3915. However, the cleaner logic for writing compressed messages (in case some messages in the message set were not retained) writes the topic message format version in the magic field of the outer message instead of the actual message format. The choice of the absolute/relative offset for the inner messages will also be based on the topic message format version.

      For example, if there is an old compressed message set with magic=0 in the log and the topic is configured for magic=1, then after cleaning, the new message set will have a wrapper with magic=1, the nested messages will still have magic=0, but the message offsets will be relative. If this happens, there does not seem to be an easy way to recover without manually fixing up the log.

      The offsets still work correctly as both the clients and broker use the outer message format version to decide if the relative offset needs to be converted to an absolute offset. So the main problem turns out to be that `ByteBufferMessageSet.deepIterator` throws an exception if there is a mismatch between outer and inner message format version.

      if (newMessage.magic != wrapperMessage.magic)
                throw new IllegalStateException(s"Compressed message has magic value ${wrapperMessage.magic} " +
                  s"but inner message has magic value ${newMessage.magic}")


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              hachikuji Jason Gustafson
              hachikuji Jason Gustafson
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