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https://issues.apache.org/jira/browse/KAFKA-7297?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16722217#comment-16722217
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Jun Rao commented on KAFKA-7297:
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[~lindong], good points. The current implementation is not causing severe
issues, but is not ideal. It seems it will be much easier to reason about this
api if we simply return a non-overlapping, monotonically increasing, and
unchangeable segment list. If we go with this route, it will be useful to add
some document so that we are aware of the potential performance impact for
future usage.
> Both read/write access to Log.segments should be protected by lock
> ------------------------------------------------------------------
>
> Key: KAFKA-7297
> URL: https://issues.apache.org/jira/browse/KAFKA-7297
> Project: Kafka
> Issue Type: Improvement
> Reporter: Dong Lin
> Assignee: Zhanxiang (Patrick) Huang
> Priority: Major
>
> Log.replaceSegments() updates segments in two steps. It first adds new
> segments and then remove old segments. Though this operation is protected by
> a lock, other read access such as Log.logSegments does not grab lock and thus
> these methods may return an inconsistent view of the segments.
> As an example, say Log.replaceSegments() intends to replace segments [0,
> 100), [100, 200) with a new segment [0, 200). In this case if Log.logSegments
> is called right after the new segments are added, the method may return
> segments [0, 200), [100, 200) and messages in the range [100, 200) may be
> duplicated if caller choose to enumerate all messages in all segments
> returned by the method.
> The solution is probably to protect read/write access to Log.segments with
> read/write lock.
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