[jira] [Created] (IO-802) Restore threadlocal for skipfully() byte buffer

["Tim Allison (Jira)" <ji...@apache.org>]

Tim Allison created IO-802:
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             Summary: Restore threadlocal for skipfully() byte buffer
                 Key: IO-802
                 URL: https://issues.apache.org/jira/browse/IO-802
             Project: Commons IO
          Issue Type: Bug
            Reporter: Tim Allison


Over on TIKA-4065, we found that trying to upgrade to commons-io 2.12.0 or 2.13.0 caused one of our unit tests to fail.  We found that dropping {{threadlocal}} on the buffer used in IOUtils.skipFully() in conjunction with Java's InflaterInputStream was the cause of the problem.

Our unit test shows that running skipFully() on a stream and then reading gets different results on the same underlying stream when running multithreaded.  This is really bad.  It appears to be confined to InflaterInputStream...so not a very common case.

On the [commons-io's user list|https://lists.apache.org/thread/rxfyxqochnj7bw75nr2v7hf5qtkogx7d] [~psteitz] observed that Java's InflaterInputStream expects read access to the byte array passed in...so having multiple threads writing to the same static (not-thread local) byte array is dangerous.  The behavior of Java's InflaterInputStream is surprising and not documented.

I have a demonstration of the problem here: https://github.com/tballison/commons-io/blob/TIKA-4065/src/test/java/org/apache/commons/io/IOUtilsMultithreadedTest.java





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