[jira] [Commented] (HDFS-6315) Decouple recording edit logs from FSDirectory

["Daryn Sharp (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HDFS-6315?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13987703#comment-13987703 ] 

Daryn Sharp commented on HDFS-6315:
-----------------------------------

I haven't throughly examined the patch.  I think moving the edit calls up to FSN makes sense.  I'm a bit uneasy about leaking the fsd locking up into the fsn.  That should be an internal implementation detail of the fsd.  I see that snapshots are locking it but that's due to reuse/abuse of the lock to protect the snapshot manager.  I don't think the pattern should be replicated to all operations.

> Decouple recording edit logs from FSDirectory
> ---------------------------------------------
>
>                 Key: HDFS-6315
>                 URL: https://issues.apache.org/jira/browse/HDFS-6315
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>            Reporter: Haohui Mai
>            Assignee: Haohui Mai
>         Attachments: HDFS-6315.000.patch, HDFS-6315.001.patch
>
>
> Currently both FSNamesystem and FSDirectory record edit logs. This design requires both FSNamesystem and FSDirectory to be tightly coupled together to implement a durable namespace.
> This jira proposes to separate the responsibility of implementing the namespace and providing durability with edit logs. Specifically, FSDirectory implements the namespace (which should have no edit log operations), and FSNamesystem implement durability by recording the edit logs.



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