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From "Brandon Li (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3300) stream the edit segments to NameNode when NameNode starts up
Date Thu, 19 Apr 2012 20:46:41 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3300?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13257801#comment-13257801
] 

Brandon Li commented on HDFS-3300:
----------------------------------

{quote}What is the plan of action when there are errors in streaming? NN will shutdown with
error?{quote}
If there are errors in streamed data, the NN can reload the namespace with a different active
journal service. If NN gets errors with all active journal services, it can shutdown.

{quote}Will the streamed edits also be dumped to disk in parallel? So that next time around
they are available locally instead of having to stream them again.{quote}
Caching a copy of the edit segment can be helpful when NN doesn't have new checkpoint before
its next reboot. Otherwise the cached edit segments will not be used for the next NN startup.

                
> stream the edit segments to NameNode when NameNode starts up
> ------------------------------------------------------------
>
>                 Key: HDFS-3300
>                 URL: https://issues.apache.org/jira/browse/HDFS-3300
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: ha, name-node
>            Reporter: Brandon Li
>
> Edit logs are saved on Journal daemon. When NameNode starts, it loads the latest image
file and then streams the edit logs from an active Journal daemon. 
> Currently we are using http to transfer edit files between two journal daemons/nodes
or between a journal daemon and a NameNode. To get edit file from Journal daemon, the NameNode
has to download it first and then read it from the disk.
> To avoid the slow start-up time, NameNode should be enhance to read the http data stream
and update its in memory name space instead of saving the streamed data on disk first.

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