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From "Colin Patrick McCabe (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3456) blockReportInterval is long value but when we take the random value it uses getRandom().nextInt,it is causing frequently BR
Date Fri, 25 May 2012 23:11:23 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3456?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13283804#comment-13283804
] 

Colin Patrick McCabe commented on HDFS-3456:
--------------------------------------------

Hi Nicholas,

I appreciate you taking the time to look at this (minor) JIRA and the bugs you found in my
code.

I feel like there are a lot of issues similar to this lurking in the code where we cast between
long and int.  It is simply not a good practice to perform unchecked typecasts.  The lack
of a nextLong() method tends to produce this kind of code.  For that reason alone, it would
be a good addition to Hadoop-- don't you agree?

Check out HDFS-2541, where we also needed a nextRandomLong, didn't have it, and ended up doing
an (incorrect) typecast.  The problem is more widespread than you think.  Does that make sense
at all?  The alternative is to change a lot of our long configuration values to int, or introduce
artificial maximum values for them.
                
> blockReportInterval is long value but when we take the random value it uses getRandom().nextInt,it
is causing frequently BR
> ---------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-3456
>                 URL: https://issues.apache.org/jira/browse/HDFS-3456
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: data-node
>    Affects Versions: 2.0.0-alpha
>            Reporter: Brahma Reddy Battula
>            Assignee: Colin Patrick McCabe
>            Priority: Minor
>         Attachments: HDFS-3456.001.patch
>
>
> blockReportInterval is long value but when we take the random value it uses getRandom().nextInt.
> Due to this, offerService can throw exception as long may get rotated to negative value.
> So, block report may send very frequently.
> {code}
>       if (resetBlockReportTime) {
>         lastBlockReport = startTime - DFSUtil.getRandom().nextInt((int)(dnConf.blockReportInterval));
>       resetBlockReportTime = false;
> {code}

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