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https://issues.apache.org/jira/browse/KAFKA-15609?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17775761#comment-17775761
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Ismael Juma commented on KAFKA-15609:
-------------------------------------
If you use buffered io (not direct io), you still go via the page cache. But if
you do not fsync, it's possible for the disk stage to diverge from the uploaded
state after a crash (for example).
> Corrupted index uploaded to remote tier
> ---------------------------------------
>
> Key: KAFKA-15609
> URL: https://issues.apache.org/jira/browse/KAFKA-15609
> Project: Kafka
> Issue Type: Bug
> Components: Tiered-Storage
> Affects Versions: 3.6.0
> Reporter: Divij Vaidya
> Priority: Minor
>
> While testing Tiered Storage, we have observed corrupt indexes being present
> in remote tier. One such situation is covered here at
> https://issues.apache.org/jira/browse/KAFKA-15401. This Jira presents another
> such possible case of corruption.
> Potential cause of index corruption:
> We want to ensure that the file we are passing to RSM plugin contains all the
> data which is present in MemoryByteBuffer i.e. we should have flushed the
> MemoryByteBuffer to the file using force(). In Kafka, when we close a
> segment, indexes are flushed asynchronously [1]. Hence, it might be possible
> that when we are passing the file to RSM, the file doesn't contain flushed
> data. Hence, we may end up uploading indexes which haven't been flushed yet.
> Ideally, the contract should enforce that we force flush the content of
> MemoryByteBuffer before we give the file for RSM. This will ensure that
> indexes are not corrupted/incomplete.
> [1]
> [https://github.com/apache/kafka/blob/4150595b0a2e0f45f2827cebc60bcb6f6558745d/core/src/main/scala/kafka/log/UnifiedLog.scala#L1613]
>
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