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From "Hiroshi Ikeda (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-14873) Problems around BoundedByteBufferPool providing direct buffers
Date Tue, 01 Dec 2015 01:52:11 GMT

    [ 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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