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https://issues.apache.org/jira/browse/KAFKA-727?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13560402#comment-13560402
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Jun Rao commented on KAFKA-727:
-------------------------------
One way to fix this is for FileMessageSet.searchFor() to return
OffsetPosition(-1L, the value of size) if offset is not found, instead of
returning null. In LogSegment.read(), we can use the returned position to guard
the length of messageSet.read.
> broker can still expose uncommitted data to a consumer
> ------------------------------------------------------
>
> Key: KAFKA-727
> URL: https://issues.apache.org/jira/browse/KAFKA-727
> Project: Kafka
> Issue Type: Bug
> Components: core
> Affects Versions: 0.8
> Reporter: Jun Rao
> Priority: Blocker
>
> Even after kafka-698 is fixed, we still see consumer clients occasionally see
> uncommitted data. The following is how this can happen.
> 1. In Log.read(), we pass in startOffset < HW and maxOffset = HW.
> 2. Then we call LogSegment.read(), in which we call translateOffset on the
> maxOffset. The offset doesn't exist and translateOffset returns null.
> 3. Continue in LogSegment.read(), we then call messageSet.sizeInBytes() to
> fetch and return the data.
> What can happen is that between step 2 and step 3, a new message is appended
> to the log and is not committed yet. Now, we have exposed uncommitted data to
> the client.
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