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Date: Mon, 9 Apr 2012 22:23:19 +0000 (UTC)
From: "Brandon Li (Commented) (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
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Subject: [jira] [Commented] (HDFS-3229) add JournalProtocol RPCs to list
 finalized edit segments, and read edit segment file from JournalNode.
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    [ https://issues.apache.org/jira/browse/HDFS-3229?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13250249#comment-13250249 ] 

Brandon Li commented on HDFS-3229:
----------------------------------

Todd, 
Reusing existing code has certain benefits for sure. 
Have an HTTP server for JournalNode requires additional port. In a large cluster, it may not be trivial to manager one more port. 

However, if we believe we need web UI for JournalNode, we need the port anyways.

Suppose we used HTTP server to synchronize the lagging JournalNode by downloading missed edit logs from another Journal Node. Firstly, the lagging JN needs to get (e.g., by asking for NN) a list of JNs with full set of edit logs. Then, it downloads the missed logs from a good JN through http, while it could accept streamed logs from NN through rpc at the same time. Given the two servers are working on different file sets(finalized logs vs in-progress log), synchronizing them seems not a concern.

Debug-ability in this case has more to do with the developer's familiarity with the code/protocol, and seems not a good enough reason to me now. 

Please let me know what you think.
                
> add JournalProtocol RPCs to list finalized edit segments, and read edit segment file from JournalNode. 
> -------------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-3229
>                 URL: https://issues.apache.org/jira/browse/HDFS-3229
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: ha, name-node
>            Reporter: Brandon Li
>            Assignee: Brandon Li
>


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