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https://issues.apache.org/jira/browse/HDFS-11448?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15995387#comment-15995387
 ] 

Jing Zhao commented on HDFS-11448:
----------------------------------

Thanks for continuing working on this, [~hanishakoneru]. And thanks for the 
review, [~arpitagarwal]. I have 2 further minor comments:
# I'm not very sure if we still need to check if the current directory exists 
when starting a sync iteration. We have already checked if current directory 
exists while initializing the journal. Then during the upgrade/rollback, both 
the {{moveTmpSegmentToCurrent}} and {{doRollback}} hold the Journal object's 
monitor, {{moveTmpSegmentToCurrent}} also checks the {{committedTxnId}} before 
moving. Thus to me it is not necessary to have this current directory check in 
{{canJournalSync}}.
{code}
  public boolean canJournalSync() {
    // JN should not sync if there is no current directory (during upgrade or
    // rollback).
      return storage.getCurrentDir().exists();
  }
{code}
# About the name of the temporary directory: maybe we can have a more specific 
name like "edits.tmp" or "edits.sync"? 

Otherwise the patch looks good to me.

> JN log segment syncing should support HA upgrade
> ------------------------------------------------
>
>                 Key: HDFS-11448
>                 URL: https://issues.apache.org/jira/browse/HDFS-11448
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: hdfs
>            Reporter: Hanisha Koneru
>            Assignee: Hanisha Koneru
>         Attachments: HDFS-11448.001.patch
>
>
> HDFS-4025 adds support for sychronizing past log segments to JNs that missed 
> them. But, as pointed out by [~jingzhao], if the segment download happens 
> when an admin tries to rollback, it might fail ([see 
> comment|https://issues.apache.org/jira/browse/HDFS-4025?focusedCommentId=15850633&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-15850633]).



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