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Date: Fri, 18 Jun 2010 20:10:25 -0400 (EDT)
From: "dhruba borthakur (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Subject: [jira] Commented: (HDFS-1245) Plugable block id generation
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    [ https://issues.apache.org/jira/browse/HDFS-1245?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12880379#action_12880379 ] 

dhruba borthakur commented on HDFS-1245:
----------------------------------------

Maybe you can write up just the proposed Interface class (with empty methods) along with an imbedded javadoc docs? That might help in understanding this proposal.

> Plugable block id generation 
> -----------------------------
>
>                 Key: HDFS-1245
>                 URL: https://issues.apache.org/jira/browse/HDFS-1245
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>          Components: name-node
>            Reporter: Dmytro Molkov
>            Assignee: Dmytro Molkov
>
> The idea is to have a way to easily create block id generation engines that may fit a certain purpose. One of them could be HDFS-898 started by Konstantin, but potentially others.
> We chatted with Dhruba about this for a while and came up with the following approach:
> There should be a BlockIDGenerator interface that has following methods:
> void blockAdded(Block)
> void blockRemoved(Block)
> Block nextBlock()
> First two methods are needed for block generation engines that hold a certain state. During the restart, when namenode reads the fsimage it will notify generator about all the blocks it reads from the image and during runtime namenode will notify the generator about block removals on file deletion.
> The instance of the generator will also have a reference to the block registry, the interface that BlockManager implements. The only method there is __blockExists(Block)__, so that the current random block id generation can be implemented, since it needs to check with the block manager if the id is already present.
> What does the community think about this proposal?

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