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From "Steve Loughran (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-2966) TestNameNodeMetrics tests can fail under load
Date Sat, 18 Feb 2012 14:34:59 GMT

    [ https://issues.apache.org/jira/browse/HDFS-2966?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13210969#comment-13210969
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Steve Loughran commented on HDFS-2966:
--------------------------------------

A problem here is that the tests are not independent -the fs events from the previous test
can still be trickling through the filesystem when the next test starts running.

A simple poll/sleep cycle actually behaves worse, because it can exit too early; the state
of the previous test is still there and the more recent changes aren't yet in the metrics.


A sleep+ followup poll cycle would appear to be a better process, though it may still have
problems under load that movind to per-test mini HDFS clusters would be required to fix.
                
> TestNameNodeMetrics tests can fail under load
> ---------------------------------------------
>
>                 Key: HDFS-2966
>                 URL: https://issues.apache.org/jira/browse/HDFS-2966
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: test
>    Affects Versions: 0.24.0
>         Environment: OS/X running intellij IDEA, firefox, winxp in a virtualbox.
>            Reporter: Steve Loughran
>            Assignee: Steve Loughran
>            Priority: Minor
>
> I've managed to recreate HDFS-540 and HDFS-2434 by the simple technique of running the
HDFS tests on a desktop with out enough memory for all the programs trying to run. Things
got swapped out and the tests failed as the DN heartbeats didn't come in on time.
> the tests both rely on {{waitForDeletion()}} to block the tests until the delete operation
has completed, but all it does is sleep for the same number of seconds as there are datanodes.
This is too brittle -it may work on a lightly-loaded system, but not on a system under heavy
load where it is taking longer to replicate than expect.
> Immediate fix: double, triple, the sleep time?
> Better fix: have the thread block until all the DN heartbeats have finished.

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