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From "Anoop Sam John (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-14873) Problems around BoundedByteBufferPool providing direct buffers
Date Thu, 03 Dec 2015 05:15:11 GMT

    [ https://issues.apache.org/jira/browse/HBASE-14873?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15037272#comment-15037272
] 

Anoop Sam John commented on HBASE-14873:
----------------------------------------

Endianness is considered.  We always write data in big endian way irrespective of the system.
Read time also we take care to reverse bytes in case needed.

'Alignment '  - Yes let us check this more..  The unsafe way of reading from on heap buffers/
byte arrays is there from long time. And we added it for off heap also recently.  We need
to check it once.  

So my suggestion, let us commit this fix which is fixing a critical issue.  Then we check
more on making the Unsafe way of copying really 'safe'

> Problems around BoundedByteBufferPool providing direct buffers
> --------------------------------------------------------------
>
>                 Key: HBASE-14873
>                 URL: https://issues.apache.org/jira/browse/HBASE-14873
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Hiroshi Ikeda
>            Assignee: Hiroshi Ikeda
>         Attachments: HBASE-14873-V2.patch, HBASE-14873.patch, HBASE-14873.patch, HBASE-14873.patch
>
>
> HBASE-13819 made BoundedByteBufferPool provide direct buffers.
> See RpcServer.java:
> {code}
> ...
> class Call implements RpcCallContext {
>   protected synchronized void setResponse(...) {
> ...
>     this.cellBlock = ipcUtil.buildCellBlock(..., reservoir);
> ...
>     bc = new BufferChain(..., this.cellBlock);
>     if (connection.useWrap) {
>       bc = wrapWithSasl(bc);
>     }
> ...
>   private BufferChain wrapWithSasl(BufferChain bc) throws IOException {
> ...
>     byte[] responseBytes = bc.getBytes();
> ...
> {code}
> {{cellBlock}} is expected to be a direct buffer retrieved from {{reservoir}} (but not
always), and {{bc}} may be composed of both direct and non-direct buffers.
> And then, see BufferChain.java:
> {code}
> byte [] getBytes() {
> ...
>     for (ByteBuffer bb: this.buffers) {
>       System.arraycopy(bb.array(), ...);
> {code}
> A direct buffer doesn't give its array, and will throw UnsupportedOperationException.
> Another problem; {{cellBlock}} is allowed to be a non-direct buffer, and after use it
will be put to {{reservoir}}, mixing direct and non-direct buffers in the pool.



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