[HADOOP-18193] Support nested mount points in INodeTree

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.10.0
• Fix Version/s: 3.4.0
• Component/s: viewfs
• Labels: pull-request-available
• Target Version/s: 3.4.0
• Hadoop Flags: Reviewed
• Assignee: Lei Yang
• Reporter: Lei Yang
• Created: 05/Apr/22 16:40
• Updated: 28/Jan/24 08:28
• Resolved: 12/May/22 00:03

Description

Defining following client mount table config is not supported in  INodeTree and will throw FileAlreadyExistsException

 

fs.viewfs.mounttable.link./foo/bar=hdfs://nn1/foo/bar
fs.viewfs.mounttable.link./foo=hdfs://nn02/foo

INodeTree has 2 methods that need change to support nested mount points.

createLink(): build INodeTree during fs init.
resolve(): resolve path in INodeTree with viewfs apis.

ViewFileSystem and ViewFs maintains an INodeTree instance(fsState) in both classes and call fsState.resolve(..) to resolve path to specific mount point. INodeTree.resolve encapsulates the logic of nested mount point resolving. So no changes are expected in both classes. 

AC:

1. INodeTree.createlink should support creating nested mount points.(INodeTree is constructed during fs init)
2. INodeTree.resolve should support resolve path based on nested mount points. (INodeTree.resolve is used in viewfs apis)
3. No regression in existing ViewFileSystem and ViewFs apis.
4. Ensure some important apis are not broken with nested mount points. (Rename, getContentSummary, listStatus...)

 

Spec:

Please review attached pdf for spec about this feature.

Issue Links

• links to: GitHub Pull Request #4181