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Date: Tue, 1 Dec 2015 01:52:11 +0000 (UTC)
From: "Hiroshi Ikeda (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
Message-ID: <JIRA.12915717.1448354692000.227035.1448934731140@Atlassian.JIRA>
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 <JIRA.12915717.1448354692626@arcas>
Subject: [jira] [Commented] (HBASE-14873) Problems around
 BoundedByteBufferPool providing direct buffers
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    [ https://issues.apache.org/jira/browse/HBASE-14873?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15032880#comment-15032880 ] 

Hiroshi Ikeda commented on HBASE-14873:
---------------------------------------

{quote}
This might have grown to bigger size but then also we will recreate DBB when the original one (got from pool) was DBB
{quote}

Ops, my bad. I jumped a wrong conclusion. Now,

{quote}
The issue with BufferChain#getBytes () can fixed with simple fix no?  Why this much changes? Am I missing some thing?
{quote}

I agree. My patch involves improvement to reuse all direct buffers, which is not appropriate to just fix the bug. I was too nervous of throwing them away, and I'll create a new patch.

{quote}
bq. The purpose of BoudnedByteBufferPool becomes vague. 
How is it vague [~ikeda]?
{quote}

I mean, we should manage direct buffers and non-direct buffers in different ways, which requires us to write codes in different ways, and I don't find a place to use BoundedByteBufferPool with switching direct/non-direct buffers later.

> 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
>             Fix For: 2.0.0
>
>         Attachments: 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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