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Date: Fri, 20 Feb 2015 06:13:12 +0000 (UTC)
From: "zhangduo (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (HBASE-13070) Fix TestCacheOnWrite
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    [ https://issues.apache.org/jira/browse/HBASE-13070?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14328605#comment-14328605 ] 

zhangduo commented on HBASE-13070:
----------------------------------

Oh I think I found the problem.

We turned on hfile prefetching in this test after HBASE-12270(maybe a mistake).
See https://builds.apache.org/job/HBase-TRUNK/6110/artifact/hbase-server/target/surefire-reports/org.apache.hadoop.hbase.io.hfile.TestCacheOnWrite-output.txt
{noformat}
2015-02-10 06:48:00,128 DEBUG [main] hfile.PrefetchExecutor(102): Prefetch requested for /home/jenkins/jenkins-slave/workspace/HBase-TRUNK/hbase-server/target/test-data/170a3172-9a2e-4269-8085-8433f46141c6/test_cache_on_write/b7d5cfcd4b57411eaac3ebbb83626249, delay=905 ms
{noformat}
And see https://builds.apache.org/job/HBase-TRUNK/5796/artifact/hbase-server/target/surefire-reports/org.apache.hadoop.hbase.io.hfile.TestCacheOnWrite-output.txt
Grep "Prefetch requested for" and get nothing.

And we can see that, the prefetch operation has a delay, usually nearly 1 sec in tests, so if the test run fast enough then there is no problem. But if we run the test on a slow machine then BlockCache maybe ruined before we finish checking cached blocks and make the test fail.

Thanks [~tedyu] to let me add a log when clearing BlockCache multiple times then I found the actual issue.

> Fix TestCacheOnWrite
> --------------------
>
>                 Key: HBASE-13070
>                 URL: https://issues.apache.org/jira/browse/HBASE-13070
>             Project: HBase
>          Issue Type: Bug
>          Components: test
>    Affects Versions: 2.0.0
>            Reporter: zhangduo
>            Assignee: zhangduo
>         Attachments: HBASE-13070.patch
>
>
> TestCacheOnWrite uses TestHFileWriterV2.randomOrderedKey to generate a random byte array, then use first 32 bytes as row and remaining part as family and qualifier. But TestHFileWriterV2.randomOrderedKey may return a byte array only contains 32 bytes, so there will be zero length family and qualifier.


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