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https://issues.apache.org/jira/browse/HADOOP-19167?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17844920#comment-17844920
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ASF GitHub Bot commented on HADOOP-19167:
-----------------------------------------

skyskyhu closed pull request #6798: HADOOP-19167 Bug Fix: Change of Codec 
configuration does not work
URL: https://github.com/apache/hadoop/pull/6798




> Change of Codec configuration does not work
> -------------------------------------------
>
>                 Key: HADOOP-19167
>                 URL: https://issues.apache.org/jira/browse/HADOOP-19167
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: compress
>            Reporter: Zhikai Hu
>            Priority: Minor
>              Labels: pull-request-available
>
> In one of my projects, I need to dynamically adjust compression level for 
> different files. 
> However, I found that in most cases the new compression level does not take 
> effect as expected, the old compression level continues to be used.
> Here is the relevant code snippet:
> ZStandardCodec zStandardCodec = new ZStandardCodec();
> zStandardCodec.setConf(conf);
> conf.set("io.compression.codec.zstd.level", "5"); // level may change 
> dynamically
> conf.set("io.compression.codec.zstd", zStandardCodec.getClass().getName());
> writer = SequenceFile.createWriter(conf, 
> SequenceFile.Writer.file(sequenceFilePath),
>                                 
> SequenceFile.Writer.keyClass(LongWritable.class),
>                                 
> SequenceFile.Writer.valueClass(BytesWritable.class),
>                                 
> SequenceFile.Writer.compression(CompressionType.BLOCK));
> The reason is SequenceFile.Writer.init() method will call 
> CodecPool.getCompressor(codec, null) to get a compressor. 
> If the compressor is a reused instance, the conf is not applied because it is 
> passed as null:
> public static Compressor getCompressor(CompressionCodec codec, Configuration 
> conf) {
> Compressor compressor = borrow(compressorPool, codec.getCompressorType());
> if (compressor == null)
> { compressor = codec.createCompressor(); LOG.info("Got brand-new compressor 
> ["+codec.getDefaultExtension()+"]"); }
> else {
> compressor.reinit(conf);   //conf is null here
> ......
>  
> Please also refer to my unit test to reproduce the bug. 
> To address this bug, I modified the code to ensure that the configuration is 
> read back from the codec when a compressor is reused.



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