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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ACCUMULO-4153) Change getCodec method in BCFile's Compression class
Date Wed, 24 Feb 2016 22:35:18 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-4153?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15165540#comment-15165540
] 

ASF GitHub Bot commented on ACCUMULO-4153:
------------------------------------------

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.


> Change getCodec method in BCFile's Compression class
> ----------------------------------------------------
>
>                 Key: ACCUMULO-4153
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-4153
>             Project: Accumulo
>          Issue Type: Improvement
>          Components: core
>    Affects Versions: 1.6.5
>            Reporter: marco polo
>            Assignee: marco polo
>            Priority: Minor
>             Fix For: 1.6.6, 1.7.2, 1.8.0
>
>         Attachments: patchCompression
>
>
> Seeing major blockages blockages on the Synchronized method of getCodec.  My initial
change was to change it to double checked locking; however, spoke with [~kturner] and I'm
changing this to an AtomicReference. Have a patch for the former but am in the process of
testing the AtomicReference patch
> Note this is for Gzip



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