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From "Jun Rao (JIRA)" <j...@apache.org>
Subject [jira] [Created] (KAFKA-727) broker can still expose uncommitted data to a consumer
Date Wed, 23 Jan 2013 05:22:12 GMT
Jun Rao created KAFKA-727:

             Summary: 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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