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From "Uma Maheswara Rao G (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-1599) Umbrella Jira for Improving HBASE support in HDFS
Date Fri, 30 Mar 2012 13:20:29 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1599?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13242322#comment-13242322
] 

Uma Maheswara Rao G commented on HDFS-1599:
-------------------------------------------

Other point I wanted to mention is, Presently HBase using lot of reflection based invocations
to call HDFS methods( which are not exposed).

Ex: 
{code}Field fIn = FilterInputStream.class.getDeclaredField("in");
            fIn.setAccessible(true);
            Object realIn = fIn.get(this.in);
            // In hadoop 0.22, DFSInputStream is a standalone class.  Before this,
            // it was an inner class of DFSClient.
            if (realIn.getClass().getName().endsWith("DFSInputStream")) {
              Method getFileLength = realIn.getClass().
                getDeclaredMethod("getFileLength", new Class<?> []{});
              getFileLength.setAccessible(true);
              long realLength = ((Long)getFileLength.
                invoke(realIn, new Object []{})).longValue();{code}



What is plan for support in exposing some kind of real usage details to dependant components
through some special interfaces?

I can see that, lot of code filled with reflection based invocations in Hbase.
That will really make harder in version migrations later. Since they are internal APIs HDFS
may change very easily. But Hbase might depend on them tightly. In such cases, Hbase will
face lot of difficultuies in migrating to newer versions.

Let's start brainstorming on this issue here.
                
> Umbrella Jira for Improving HBASE support in HDFS
> -------------------------------------------------
>
>                 Key: HDFS-1599
>                 URL: https://issues.apache.org/jira/browse/HDFS-1599
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>            Reporter: Sanjay Radia
>
> Umbrella Jira for improved HBase support in HDFS

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