[jira] [Work started] (HBASE-27637) Zero length value would cause value compressor read nothing nad 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 ]

Work on HBASE-27637 started by Duo Zhang.
-----------------------------------------
> Zero length value would cause value compressor read nothing nad 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
>
> 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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