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From brianloss <...@git.apache.org>
Subject [GitHub] accumulo pull request: ACCUMULO-4153: Update the getCodec method t...
Date Wed, 24 Feb 2016 22:35:21 GMT
Github user brianloss commented on a diff in the pull request:

    https://github.com/apache/accumulo/pull/73#discussion_r54019025
  
    --- Diff: core/src/main/java/org/apache/accumulo/core/file/rfile/bcfile/Compression.java
---
    @@ -147,25 +148,27 @@ public synchronized OutputStream createCompressionStream(OutputStream
downStream
         },
     
         GZ(COMPRESSION_GZ) {
    -      private transient DefaultCodec codec;
    +      private transient AtomicReference<DefaultCodec> codec = new AtomicReference<DefaultCodec>();
     
           @Override
    -      synchronized CompressionCodec getCodec() {
    -        if (codec == null) {
    -          codec = new DefaultCodec();
    -          codec.setConf(conf);
    +      CompressionCodec getCodec() {
    +        DefaultCodec resultCodec = codec.get();
    +        if (null == resultCodec) {
    +          DefaultCodec newCodec = new DefaultCodec();
    --- End diff --
    
    If a bunch of threads all got to this point at the same time, they would all create a
new DefaultCodec. Only one will succeed on the compareAndSet below, but the code is still
potentially creating many DefaultCodec instances which will get garbage collected.
    Since isSupported returns true, I'm wondering if it's possible to simply initialize the
member variable at construction time, and then the AtomicReference wouldn't be needed either?
But maybe I'm missing something obvious.


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