Page History

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1. Bump up ProducerRequest and FetchRequest version to V2, which uses MessageAndOffset V1.
    
2. Upgrade broker to support both ProducerRequest and FetchRequest V2 which uses magic byte 1 for MessageAndOffset.
   
   1. When broker sees a producer request V1 (MessageAndOffset = V0), it will decompress the message, assign offsets using relative offsets and re-compress the message, set CreateTime=-1. i.e. upconvert the message format to mag.
      
   2. When broker sees a producer request V2 (MessageAndOffset = V1), it will decompress the message for verification, assign the offset to outer message and NOT do recompression. 
   3. When broker sees a fetch request V1 (MessageAndOffset = V0), because the data format on disk is MessageAndOffset V1, it will no use the zero-copy transfer, but read the message to memory, do down-conversion, then send fetch response V1.
   4. When broker sees a fetch request V2 (MessageAndOffset = V1), it will use zero-copy transfer to reply with fetch response V2.
      
3. Upgrade consumer to support both V0 and V1.
4. Upgrade producer to send MessageAndOffset V1.

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