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From "Brandon Li (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3186) Sync lagging journal service from the active journal service
Date Thu, 03 May 2012 00:07:50 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3186?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13267049#comment-13267049

Brandon Li commented on HDFS-3186:

{quote}Why do you want to throw IllegalStateException in inSync() method?{quote}
I don't think I get the question. do we want to fail in a different way here?
{quote}Why should syncThread be a never ending thread?{quote}
It is because sync may be required anytime due to NN failover or journal service failure.
If it's not a never ending thread, journal service needs to spawn sync thread on demand and
lets the sync thread exit when sync is done. Both approaches need to handle the same set of
situations, such as, the journal service state changes before sync finishes. The communication
between main thread and sync thread is strait forward in both cases, and the never-ending-thread
approach can avoid the cost of repeated thread creation.    
{quote}There are bunch of TODO items{quote}
One cause of the TODOs is that, the NN is not updated to cooperate with journal service.
{quote}Why would syncThread be not null in run() method?{quote}
removed this check. I was over cautious there.
{quote}runSync - startSync name better? valueSet may not be needed?{quote}
changed name. removed valueSet since it's redundent with another veriable.

Other comments are addressed.
> Sync lagging journal service from the active journal service
> ------------------------------------------------------------
>                 Key: HDFS-3186
>                 URL: https://issues.apache.org/jira/browse/HDFS-3186
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: ha, name-node
>            Reporter: Hari Mankude
>            Assignee: Brandon Li
>         Attachments: HDFS-3186.HDFS-3092.patch, HDFS-3186.HDFS-3092.patch

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