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https://issues.apache.org/jira/browse/KAFKA-8522?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17416231#comment-17416231
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Jun Rao commented on KAFKA-8522:
--------------------------------

The implementation design can be found at KIP-534: 
[https://cwiki.apache.org/confluence/display/KAFKA/KIP-534%3A+Retain+tombstones+and+transaction+markers+for+approximately+delete.retention.ms+milliseconds]

> Tombstones can survive forever
> ------------------------------
>
>                 Key: KAFKA-8522
>                 URL: https://issues.apache.org/jira/browse/KAFKA-8522
>             Project: Kafka
>          Issue Type: Improvement
>          Components: log cleaner
>            Reporter: Evelyn Bayes
>            Assignee: Richard Yu
>            Priority: Minor
>             Fix For: 3.1.0
>
>
> This is a bit grey zone as to whether it's a "bug" but it is certainly 
> unintended behaviour.
>  
> Under specific conditions tombstones effectively survive forever:
>  * Small amount of throughput;
>  * min.cleanable.dirty.ratio near or at 0; and
>  * Other parameters at default.
> What  happens is all the data continuously gets cycled into the oldest 
> segment. Old records get compacted away, but the new records continuously 
> update the timestamp of the oldest segment reseting the countdown for 
> deleting tombstones.
> So tombstones build up in the oldest segment forever.
>  
> While you could "fix" this by reducing the segment size, this can be 
> undesirable as a sudden change in throughput could cause a dangerous number 
> of segments to be created.



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