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From ivakegg <...@git.apache.org>
Subject [GitHub] accumulo pull request #134: ACCUMULO-4391 Added synchronization around the a...
Date Thu, 28 Jul 2016 00:01:22 GMT
Github user ivakegg commented on a diff in the pull request:

    https://github.com/apache/accumulo/pull/134#discussion_r72545819
  
    --- Diff: core/src/main/java/org/apache/accumulo/core/file/rfile/bcfile/BoundedRangeFileInputStream.java
---
    @@ -62,12 +62,15 @@ public BoundedRangeFileInputStream(FSDataInputStream in, long offset,
long lengt
     
       @Override
       public int available() throws IOException {
    -    int avail = in.available();
    -    if (pos + avail > end) {
    -      avail = (int) (end - pos);
    -    }
    +    final FSDataInputStream inLocal = in;
    +    synchronized (inLocal) {
    +      int avail = in.available();
    --- End diff --
    
    Absolutely correct, as I had eluded to in the ticket.  This is why I tracked where that
method is being invoked.  The only place I found was in the hadoop CompressionInputStream
where the returned value is used in the CompressionInputStream.getPos() call which is never
actually used.  That being said, using any InputStream in multiple threads is inherently unsafe
given its API.
    So I could completely rewrite this mechanism to not reuse the same underlying stream.
 Alternatively I could create a map that keeps track of threads and the position in the stream.
 Do you think that is worth the overhead for a method whose value is not actually used?


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