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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-12295) Prevent block eviction under us if reads are in progress from the BBs
Date Wed, 15 Jul 2015 05:27:05 GMT

    [ https://issues.apache.org/jira/browse/HBASE-12295?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14627551#comment-14627551
] 

stack commented on HBASE-12295:
-------------------------------

Out of interest, server-side, how many Interfaces and abstract classes might a Cell implementation
be implementing now?

Nit: SharedMemoryBackedCell should be SharedMemoryCell ?

I like your removal of setters from HFileContext

Do you want to remove this:

//Empty constructor.  Go with setters
public HFileContext() 

The below comment is a little soft:

"121	   * Called when the scanner using the block decides to safely decrement
122	   * the reference count of the block since the block is no longer in use."

Should it be something like YOU MUST RETURN BLOCKS TO BC WHEN DONE!!!! OR ELSE!!!!

Should Type be MemoryType enum? (I think you or Anoop suggested this and it a good idea)..
would match the getMemoryType method in Cacheable.

I haven't poke aorund but would it make sense passing Cacheable here:

	  T deserialize(ByteBuffer b, boolean reuse, Type memType) throws IOException;

Maybe not. Just a thought.

Skimmed the rest. Let me come back to this again. Is it up in RB? I think this stuff is starting
to come together nicely.



> Prevent block eviction under us if reads are in progress from the BBs
> ---------------------------------------------------------------------
>
>                 Key: HBASE-12295
>                 URL: https://issues.apache.org/jira/browse/HBASE-12295
>             Project: HBase
>          Issue Type: Sub-task
>          Components: regionserver, Scanners
>            Reporter: ramkrishna.s.vasudevan
>            Assignee: ramkrishna.s.vasudevan
>             Fix For: 2.0.0
>
>         Attachments: HBASE-12295.pdf, HBASE-12295_1.patch, HBASE-12295_1.pdf, HBASE-12295_10.patch,
HBASE-12295_12.patch, HBASE-12295_2.patch, HBASE-12295_4.patch, HBASE-12295_4.pdf, HBASE-12295_5.pdf,
HBASE-12295_9.patch, HBASE-12295_trunk.patch
>
>
> While we try to serve the reads from the BBs directly from the block cache, we need to
ensure that the blocks does not get evicted under us while reading.  This JIRA is to discuss
and implement a strategy for the same.



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