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Date: Tue, 3 May 2011 07:50:03 +0000 (UTC)
From: "Eli Collins (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
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Subject: [jira] [Commented] (HDFS-1799) Refactor log rolling and filename
 management out of FSEditLog
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    [ https://issues.apache.org/jira/browse/HDFS-1799?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13028097#comment-13028097 ] 

Eli Collins commented on HDFS-1799:
-----------------------------------

Separating out the concerns per these three classes makes sense to me. Aside from the usefulness of the abstraction, trying to maintain the invariant that EditLogOutputStream is a small delta (eg sync'ing) wrt OutputStream and not wanting to pile more code into FSEditLog necessitates a new class. When it comes to the edits log we should be optimizing for simplicity (therefore correctness) rather than # classes etc. If JournalManager evolves towards Journal as articulated in HDFS-1850, that's fine. 

These are implementation classes, we can get something that works well for 1073 and then modify as necessary for 1850.

@Todd, I'll post detailed review feedback on your latest patch tomorrow.

> Refactor log rolling and filename management out of FSEditLog
> -------------------------------------------------------------
>
>                 Key: HDFS-1799
>                 URL: https://issues.apache.org/jira/browse/HDFS-1799
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>    Affects Versions: Edit log branch (HDFS-1073)
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>             Fix For: Edit log branch (HDFS-1073)
>
>         Attachments: 0001-Added-state-management-to-FSEditLog.patch, 0002-Standardised-error-pattern.patch, 0003-Add-JournalFactory-and-move-divert-revert-out-of-FSE.patch, HDFS-1799-all.diff, hdfs-1799.txt, hdfs-1799.txt, hdfs-1799.txt, hdfs-1799.txt
>
>
> This is somewhat similar to HDFS-1580, but less ambitious. While that JIRA focuses on pluggability, this task is simply the minimum needed for HDFS-1073:
> - Refactor the filename-specific code for rolling, diverting, and reverting log streams out of FSEditLog into a new class
> - Clean up the related code in FSEditLog a bit
> Notably, this JIRA is going to temporarily break the BackupNode. I plan to circle back on the BackupNode later on this branch.

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