Jiangtao Liu created KAFKA-8270:
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Summary: Kafka retention hour is not working
Key: KAFKA-8270
URL: https://issues.apache.org/jira/browse/KAFKA-8270
Project: Kafka
Issue Type: Improvement
Components: consumer
Reporter: Jiangtao Liu
Assignee: Richard Yu
Currently, when a consumer falls out of a consumer group, it will restart
processing from the last checkpointed offset. However, this design could result
in a lag which some users could not afford to let happen. For example, lets say
a consumer crashed at offset 100, with the last checkpointed offset being at
70. When it recovers at a later offset (say, 120), it will be behind by an
offset range of 50 (120 - 70). This is because the consumer restarted at 70,
forcing it to reprocess old data. To avoid this from happening, one option
would be to allow the current consumer to start processing not from the last
checkpointed offset (which is 70 in the example), but from 120 where it
recovers. Meanwhile, a new KafkaConsumer will be instantiated and start reading
from offset 70 in concurrency with the old process, and will be terminated once
it reaches 120. In this manner, a considerable amount of lag can be avoided,
particularly since the old consumer could proceed as if nothing had happened.
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