[jira] Commented: (HADOOP-3795) NameNode does not save image if different dfs.name.dir have different checkpoint stamps

["Lohit Vijayarenu (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-3795?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12614921#action_12614921 ] 

Lohit Vijayarenu commented on HADOOP-3795:
------------------------------------------

Here is what happened.
- There were 2 dfs.name.dir directories each with valid image and edits, but different checkpoint times
- The dir which had the latest checkpoint time had latest image and zero edits. The other directory had older image with non zero entries in edits
- So, while starting, after validating consistency of all dfs.name.dir, namenode started with latest image but ignored saving since needToSave was never set in any of the conditions.

This could be bad, sometimes. In cases if the other directory had edits.new and good directory didnt have, then checkpoint by secondary namenode would fail. 

> NameNode does not save image if different dfs.name.dir have different checkpoint stamps
> ---------------------------------------------------------------------------------------
>
>                 Key: HADOOP-3795
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3795
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: dfs
>    Affects Versions: 0.19.0
>            Reporter: Lohit Vijayarenu
>
> There is a case where namenode does not save image file during startup even if their checkpoint times are different.

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