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https://issues.apache.org/jira/browse/HDFS-6355?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13992645#comment-13992645
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Vinayakumar B commented on HDFS-6355:
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Changes looks good.
One small doubt.
{code}+ long timeLeft = Math.max(1L,
+ currentPeriodStart + scanPeriod - Time.monotonicNow());{code}
Here since we already use monotonicNow(), which is relative to jvm startup, I
don't think we will get a negative value here and hence no need to take a
max(..).
Anyway, there is no harm if its there, if you feel its fine, then I am ok with
it :), +1
> Fix divide-by-zero, improper use of wall-clock time in BlockPoolSliceScanner
> ----------------------------------------------------------------------------
>
> Key: HDFS-6355
> URL: https://issues.apache.org/jira/browse/HDFS-6355
> Project: Hadoop HDFS
> Issue Type: Bug
> Affects Versions: 2.4.0
> Reporter: Colin Patrick McCabe
> Assignee: Colin Patrick McCabe
> Attachments: HDFS-6355.001.patch
>
>
> BlockPoolSliceScanner uses {{Time.now}} to calculate an interval. But this
> is incorrect, since if the wall-clock time changes, we will end up setting
> the scan periods to a shorter or longer time than we configured.
> There is also a case where we may divide by zero if we get unlucky, because
> we calculate an interval and divide by it, without checking whether the
> interval is 0 milliseconds. This would produce an {{ArithmeticException}}
> since we are using longs.
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