[jira] [Comment Edited] (HDFS-1477) Make NameNode Reconfigurable.

["Arpit Agarwal (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HDFS-1477?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14981231#comment-14981231 ] 

Arpit Agarwal edited comment on HDFS-1477 at 10/29/15 8:43 PM:
---------------------------------------------------------------

Hi [~xiaobingo], thanks for taking this up. My comments on the v5 patch:
# FsNameSystem and DatanodeManager need not implement Reconfigurable, since their Reconfigurable methods are only invoked via NameNode.
# What does getNewConf() do? Looks like it just constructs a new config object by re-reading the config files? There should have been a Javadoc on the base class method, perhaps we can add one now.
# Can we just skip implementing reconfiguration via the servlet? A better approach is to have the daemon re-read its config files like HDFS-6808 (which you pointed out to me offline :-). Looks like you will need a new RPC call and support on the client. Also it would be good to log the reconfiguration request in the hdfs audit log.
# Nitpicks: Fix indentation in DatanodeManager#reconfigurePropertyImpl.
# {{#reconfigurePropertyImpl}} - get {{namesystem.writeLock()}} outside the {{try}} block.

Other suggestions for separate subtasks.
# The list of reconfigurable properties should not be hard-coded. We can add an annotation to the reconfigurable properties.
# Add {{ReconfigurableBase}} support for atomic updates, i.e. all or no changes take effect.
# Documentation.



was (Author: arpitagarwal):
Hi [~xiaobingo], thanks for taking this up. My comments on the v5 patch:
# FsNameSystem and DatanodeManager need implement Reconfigurable, since their Reconfigurable methods are only invoked via NameNode.
# What does getNewConf() do? Looks like it just constructs a new config object by re-reading the config files? There should have been a Javadoc on the base class method, perhaps we can add one now.
# Can we just skip implementing reconfiguration via the servlet? A better approach is to have the daemon re-read its config files like HDFS-6808 (which you pointed out to me offline :-). Looks like you will need a new RPC call and support on the client. Also it would be good to log the reconfiguration request in the hdfs audit log.
# Nitpicks: Fix indentation in DatanodeManager#reconfigurePropertyImpl.
# {{#reconfigurePropertyImpl}} - get {{namesystem.writeLock()}} outside the {{try}} block.

Other suggestions for separate subtasks.
# The list of reconfigurable properties should not be hard-coded. We can add an annotation to the reconfigurable properties.
# Add {{ReconfigurableBase}} support for atomic updates, i.e. all or no changes take effect.
# Documentation.


> Make NameNode Reconfigurable.
> -----------------------------
>
>                 Key: HDFS-1477
>                 URL: https://issues.apache.org/jira/browse/HDFS-1477
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: namenode
>    Affects Versions: 2.7.0
>            Reporter: Patrick Kling
>            Assignee: Xiaobing Zhou
>         Attachments: HDFS-1477.005.patch, HDFS-1477.2.patch, HDFS-1477.3.patch, HDFS-1477.4.patch, HDFS-1477.patch
>
>
> Modify NameNode to implement the interface Reconfigurable proposed in HADOOP-7001. This would allow us to change certain configuration properties without restarting the name node.



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