[FLINK-33153] Kafka using latest-offset maybe missing data

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Duplicate
• Component/s: Connectors / Kafka
• Assignee: Unassigned
• Reporter: tanjialiang
• Created: 25/Sep/23 09:25
• Updated: 18/Dec/23 09:31
• Resolved: 25/Sep/23 10:51

Description

When Kafka start with the latest-offset strategy, it does not fetch the latest snapshot offset and specify it for consumption. Instead, it sets the startingOffset to -1 (KafkaPartitionSplit.LATEST_OFFSET, which makes currentOffset = -1, and call the KafkaConsumer's  seekToEnd API). The currentOffset is only set to the consumed offset + 1 when the task consumes data, and this currentOffset is stored in the state during checkpointing. If there are very few messages in Kafka and a partition has not consumed any data, and I stop the task with a savepoint, then write data to that partition, and start the task with the savepoint, the task will resume from the saved state. Due to the startingOffset in the state being -1, it will cause the task to miss the data that was written before the recovery point.