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From "Lei (Eddy) Xu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-13055) Implement linkMergeSlash for ViewFileSystem
Date Thu, 21 Sep 2017 22:30:00 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-13055?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16175574#comment-16175574
] 

Lei (Eddy) Xu commented on HADOOP-13055:
----------------------------------------

Hi, [~manojg]

I am new to this I might have some misunderstanding.

{code}
// Is an internal directory
abstract boolean isInternalDir();

// Is a Merge Link or a Merge Slash Link
boolean isLink() {
   return !isInternalDir();
}
{code}
Can you add more comments here to clarify what is the concept of internal dir, and what is
the relationship between "internal dir" and {{Merge Link / Merge Slash Link}}? Or maybe rephrase
the names?

{code}
 SINGLE_FALLBACK,
MERGE_SLASH,
{code}

Can you add more comments on both of them? What is the difference?

{code}
for (LinkEntry le : linkEntries) {
if (le.isLinkType(LinkType.SINGLE_FALLBACK)) {
  INodeLink<T> fallbackLink = new INodeLink<T>(mountTableName, ugi,
  getTargetFileSystem(new URI(le.getTarget())),
   new URI(le.getTarget()));
   getRootDir().setRootFallbackLink(fallbackLink);
}
{code}

How to guarantee that there is at most one {{LinkType.SINGLE_FALLBACK}} instance.

Thanks.

> Implement linkMergeSlash for ViewFileSystem
> -------------------------------------------
>
>                 Key: HADOOP-13055
>                 URL: https://issues.apache.org/jira/browse/HADOOP-13055
>             Project: Hadoop Common
>          Issue Type: New Feature
>          Components: fs, viewfs
>    Affects Versions: 2.7.5
>            Reporter: Zhe Zhang
>            Assignee: Manoj Govindassamy
>         Attachments: HADOOP-13055.00.patch, HADOOP-13055.01.patch, HADOOP-13055.02.patch,
HADOOP-13055.03.patch, HADOOP-13055.04.patch, HADOOP-13055.05.patch, HADOOP-13055.06.patch,
HADOOP-13055.07.patch
>
>
> In a multi-cluster environment it is sometimes useful to operate on the root / slash
directory of an HDFS cluster. E.g., list all top level directories. Quoting the comment in
{{ViewFs}}:
> {code}
>  *   A special case of the merge mount is where mount table's root is merged
>  *   with the root (slash) of another file system:
>  *   <ul>
>  *   <li>    fs.viewfs.mounttable.default.linkMergeSlash=hdfs://nn99/
>  *   </ul>
>  *   In this cases the root of the mount table is merged with the root of
>  *            <b>hdfs://nn99/ </b> 
> {code}



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