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Date: Wed, 24 Feb 2016 05:39:18 +0000 (UTC)
From: "Rakesh R (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Message-ID: <JIRA.12782971.1426702773000.130265.1456292358228@Atlassian.JIRA>
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Subject: [jira] [Commented] (HDFS-7955) Improve naming of classes, methods,
 and variables related to block replication and recovery
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    [ https://issues.apache.org/jira/browse/HDFS-7955?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15160203#comment-15160203 ] 

Rakesh R commented on HDFS-7955:
--------------------------------

Thanks [~zhz].
bq. The getUnderReplicatedBlocksCount API is used by upper layer apps quite heavily, so deprecating it looks risky. I think we can leave this discussion open for a longer window to solicit feedbacks.
OK, I hope users won't get confused by seeing {{#getUnderReplicatedBlocksCount()}} API and several internal log messaging differently like,
[BlockManager.java#L3072|https://github.com/apache/hadoop/blob/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockManager.java#L3072]
{code}
LOG.info("Number of low-redundant blocks = " + nrLowRedundant);
{code}

Shall I create sub-task to start changing the identified BlockManager entities?

> Improve naming of classes, methods, and variables related to block replication and recovery
> -------------------------------------------------------------------------------------------
>
>                 Key: HDFS-7955
>                 URL: https://issues.apache.org/jira/browse/HDFS-7955
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: erasure-coding
>            Reporter: Zhe Zhang
>            Assignee: Rakesh R
>         Attachments: HDFS-7955-001.patch, HDFS-7955-002.patch, HDFS-7955-003.patch, HDFS-7955-004.patch, HDFS-7955-5.patch
>
>
> Many existing names should be revised to avoid confusion when blocks can be both replicated and erasure coded. This JIRA aims to solicit opinions on making those names more consistent and intuitive.
> # In current HDFS _block recovery_ refers to the process of finalizing the last block of a file, triggered by _lease recovery_. It is different from the intuitive meaning of _recovering a lost block_. To avoid confusion, I can think of 2 options:
> #* Rename this process as _block finalization_ or _block completion_. I prefer this option because this is literally not a recovery.
> #* If we want to keep existing terms unchanged we can name all EC recovery and re-replication logics as _reconstruction_.  
> # As Kai [suggested | https://issues.apache.org/jira/browse/HDFS-7369?focusedCommentId=14361131&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14361131] under HDFS-7369, several replication-based names should be made more generic:
> #* {{UnderReplicatedBlocks}} and {{neededReplications}}. E.g. we can use {{LowRedundancyBlocks}}/{{AtRiskBlocks}}, and {{neededRecovery}}/{{neededReconstruction}}.
> #* {{PendingReplicationBlocks}}
> #* {{ReplicationMonitor}}
> I'm sure the above list is incomplete; discussions and comments are very welcome.


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