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From "Ivan Bella (JIRA)" <j...@apache.org>
Subject [jira] [Created] (ACCUMULO-4391) Source deepcopies cannot be used safely in separate threads in tserver
Date Tue, 26 Jul 2016 19:12:20 GMT
Ivan Bella created ACCUMULO-4391:
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             Summary: 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


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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