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1. Kafka Exactly Once - Solving the problem of spurious OutOfOrderSequence errors
2. Kafka Exactly Once - Dealing with older message formats when idempotence is enabled

Public Interfaces

RecordMetadata (in 1.0.0)

With the changes in Kafka Exactly Once - Solving the problem of spurious OutOfOrderSequence errors, the broker may return a new DUPLICATE_SEQUENCE error code in some cases where a duplicate is detected but the metadata for the existing batch isn't cached in memory. When the producer receives this error, it is considered a success, but will not have the offset and timestamp information for the appended records. To help identify this state, we add  hasOffset and add hasTimestamp methods to the RecordMetadata.

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// TopicMetadataV3
 
TopicMetadata => TopicErrorCode
                 Topic
                 IsInternal
				 MessageFormatVersion
				 MaxMessageBytes
				 [PartitionMetadata]
 TopicErrorCode => int16
 Topic => String
 IsInternal => Boolean
 MessageFormatVersion => int8 (NEW)
 MaxMessageBytes => int32 (NEW)
 PartitionMetadata => PartitionMetadataV2

ProduceResponse (in 1.0.0)

We add a logStartOffset field to the produce response to help the producer identify when producer state has been lost due to retention time elapsing. See Kafka Exactly Once - Solving the problem of spurious OutOfOrderSequence errors for a precise description of how this will be used.

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