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From "Josh Elser (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ACCUMULO-4391) Source deepcopies cannot be used safely in separate threads in tserver
Date Fri, 09 Sep 2016 19:23:20 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-4391?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15478013#comment-15478013
] 

Josh Elser commented on ACCUMULO-4391:
--------------------------------------

Thanks for these last two posts, [~ivan.bella]. They are extremely helpful to understand the
big picture.

> Source deepcopies cannot be used safely in separate threads in tserver
> ----------------------------------------------------------------------
>
>                 Key: ACCUMULO-4391
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-4391
>             Project: Accumulo
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 1.6.5
>            Reporter: Ivan Bella
>            Assignee: Ivan Bella
>             Fix For: 1.6.6, 1.7.3, 1.8.1, 2.0.0
>
>   Original Estimate: 24h
>          Time Spent: 12h 50m
>  Remaining Estimate: 11h 10m
>
> We have iterators that create deep copies of the source and use them in separate threads.
 As it turns out this is not safe and we end up with many exceptions, mostly down in the ZlibDecompressor
library.  Curiously if you turn on the data cache for the table being scanned then the errors
disappear.
> After much hunting it turns out that the real bug is in the BoundedRangeFileInputStream.
 The read() method therein appropriately synchronizes on the underlying FSDataInputStream,
however the available() method does not.  Adding similar synchronization on that stream fixes
the issues.  On a side note, the available() call is only invoked within the hadoop CompressionInputStream
for use in the getPos() call.  That call does not appear to actually be used at least in this
context.



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