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Date: Tue, 23 Aug 2016 17:55:20 +0000 (UTC)
From: "Daniel Blum (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (ACCUMULO-4420) Possible divide-by-zero
 exception when closing BatchWriter
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archived-at: Tue, 23 Aug 2016 17:55:58 -0000


    [ https://issues.apache.org/jira/browse/ACCUMULO-4420?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15433291#comment-15433291 ] 

Daniel Blum commented on ACCUMULO-4420:
---------------------------------------

Small correction - an exception is not actually thrown in the 1.6.x versions due to an oddity in how Java is handling the math. In these versions the code is "tabletServersBatchSum / (double) numBatches" and somehow this ends up as NaN instead of throwing an exception.

> Possible divide-by-zero exception when closing BatchWriter
> ----------------------------------------------------------
>
>                 Key: ACCUMULO-4420
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-4420
>             Project: Accumulo
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 1.6.5, 1.7.2
>            Reporter: Daniel Blum
>            Priority: Minor
>             Fix For: 1.6.6, 1.7.3, 1.8.1
>
>
> TabletServerBatchWriter.logStats will throw a divide-by-zero exception if numBatches is 0 (i.e., no batches have been written).
> There are actually no checks for 0 divisors anywhere in the method, so other such exceptions are possible, as are lesser issues ("Average send rate" and some other stats come out as NaN when no batches have been written, for example).


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