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Date: Thu, 31 May 2012 00:18:23 +0000 (UTC)
From: "Tsz Wo (Nicholas), SZE (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
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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
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    [ https://issues.apache.org/jira/browse/HDFS-3456?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13286223#comment-13286223 ] 

Tsz Wo (Nicholas), SZE commented on HDFS-3456:
----------------------------------------------

> Well, I was going by http://docs.oracle.com/javase/1.4.2/docs/api/java/util/Random.html#nextDouble%28%29, which includes this text:

Colin, you are right that there is a bug in the 1.4.2 javadoc you read but it was already fixed in Java 6 (http://docs.oracle.com/javase/6/docs/api/java/util/Random.html#nextDouble%28%29).  They removed "All 2^53 possible float values ..."
                
> 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, HDFS-3456.002.patch, HDFS-3456.003.patch, HDFS-3456.004.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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