[jira] [Commented] (KAFKA-8522) Tombstones can survive forever

["Richard Yu (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KAFKA-8522?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16902209#comment-16902209 ] 

Richard Yu commented on KAFKA-8522:
-----------------------------------

[~junrao] You mentioned in a previous post that we should write to a checkpoint file. Should we create a new checkpoint file explicitly for storing these offsets and cleaning times? Or should it be embedded in a preexisting checkpoint file.  

> Tombstones can survive forever
> ------------------------------
>
>                 Key: KAFKA-8522
>                 URL: https://issues.apache.org/jira/browse/KAFKA-8522
>             Project: Kafka
>          Issue Type: Bug
>          Components: log cleaner
>            Reporter: Evelyn Bayes
>            Priority: Minor
>
> 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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