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From "Yongjun Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-12357) Let NameNode to bypass external attribute provider for special user
Date Sat, 02 Sep 2017 01:36:00 GMT

    [ https://issues.apache.org/jira/browse/HDFS-12357?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16151362#comment-16151362
] 

Yongjun Zhang commented on HDFS-12357:
--------------------------------------

HI [~chris.douglas],

I uploaded rev005 to avoid the {{components = Arrays.copyOfRange(components, 1, components.length);}}
overhead.

Basically I added a new API (package scope)  {{boolean isBypassUser() {}} to {{INodeAttributeProvider}}
class, and have a default implementation of returning false. Then let {{UserFilterINodeAttributeProvider}}
version to override it. Then do the following
{code}
    if (attributeProvider != null &&
        !attributeProvider.isBypassUser()) {
      // permission checking sends the full components array including the
      // first empty component for the root.  however file status
      // related calls are expected to strip out the root component according
      // to TestINodeAttributeProvider.
      byte[][] components = iip.getPathComponents();
      components = Arrays.copyOfRange(components, 1, components.length);
      nodeAttrs = attributeProvider.getAttributes(components, nodeAttrs);
    }
    return nodeAttrs;
    ......
{code}
similar to the logic as in v001. 

So here is a trade-off between not exposing the isBypassUser API and suffer the cost overhead,
vs exposing it and save the cost.

Wonder what you think?

Thanks.



> Let NameNode to bypass external attribute provider for special user
> -------------------------------------------------------------------
>
>                 Key: HDFS-12357
>                 URL: https://issues.apache.org/jira/browse/HDFS-12357
>             Project: Hadoop HDFS
>          Issue Type: Bug
>            Reporter: Yongjun Zhang
>            Assignee: Yongjun Zhang
>         Attachments: HDFS-12357.001.patch, HDFS-12357.002.patch, HDFS-12357.003.patch,
HDFS-12357.004.patch, HDFS-12357.005.patch
>
>
> This is a third proposal to solve the problem described in HDFS-12202.
> The problem is, when we do distcp from one cluster to another (or within the same cluster),
in addition to copying file data, we copy the metadata from source to target. If external
attribute provider is enabled, the metadata may be read from the provider, thus provider data
read from source may be saved to target HDFS. 
> We want to avoid saving metadata from external provider to HDFS, so we want to bypass
external provider when doing the distcp (or hadoop fs -cp) operation.
> Two alternative approaches were proposed earlier, one in HDFS-12202, the other in HDFS-12294.
The proposal here is the third one.
> The idea is, we introduce a new config, that specifies a special user (or a list of users),
and let NN bypass external provider when the current user is a special user.
> If we run applications as the special user that need data from external attribute provider,
then it won't work. So the constraint on this approach is, the special users here should not
run applications that need data from external provider.
> Thanks [~asuresh] for proposing this idea and [~chris.douglas], [~daryn], [~manojg] for
the discussions in the other jiras. 
> I'm creating this one to discuss further.



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