[jira] [Resolved] (HBASE-27637) Zero length value would cause value compressor read nothing and not advance the position of the InputStream

["Duo Zhang (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HBASE-27637?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Duo Zhang resolved HBASE-27637.
-------------------------------
    Fix Version/s: 2.6.0
                   3.0.0-alpha-4
                   2.5.4
     Hadoop Flags: Reviewed
       Resolution: Fixed

Pushed to branch-2.5+.

Thanks all for helping and reviewing!

> Zero length value would cause value compressor read nothing and not advance the position of the InputStream
> -----------------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-27637
>                 URL: https://issues.apache.org/jira/browse/HBASE-27637
>             Project: HBase
>          Issue Type: Bug
>          Components: dataloss, wal
>            Reporter: Duo Zhang
>            Assignee: Duo Zhang
>            Priority: Critical
>             Fix For: 2.6.0, 3.0.0-alpha-4, 2.5.4
>
>
> This is a code sniff from the discussion of HBASE-27073
> {code}
>   public static void main(String[] args) throws Exception {
>     CompressionContext ctx =
>       new CompressionContext(LRUDictionary.class, false, false, true, Compression.Algorithm.GZ);
>     ValueCompressor compressor = ctx.getValueCompressor();
>     byte[] compressed = compressor.compress(new byte[0], 0, 0);
>     System.out.println("compressed length: " + compressed.length);
>     ByteArrayInputStream bis = new ByteArrayInputStream(compressed);
>     int read = compressor.decompress(bis, compressed.length, new byte[0], 0, 0);
>     System.out.println("read length: " + read);
>     System.out.println("position: " + (compressed.length - bis.available()));
> {code}
> And the output is
> {noformat}
> compressed length: 20
> read length: 0
> position: 0
> {noformat}
> So it turns out that, when compressing, an empty array will still generate some output bytes but while reading, we will skip reading anything if we find the output length is zero, so next time when we read from the stream, we will start at a wrong position...



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