[HADOOP-17024] ListStatus on ViewFS root (ls "/") should list the linkFallBack root (configured target root).

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.2.2
• Fix Version/s: 3.2.2, 3.3.1, 3.4.0
• Component/s: fs, viewfs
• Target Version/s: 3.4.0
• Hadoop Flags: Incompatible change, Reviewed

Release Note

ViewFS#listStatus on root("/") considers listing from fallbackLink if available. If the same directory name is present in configured mount path as well as in fallback link, then only the configured mount path will be listed in the returned result.

• Assignee: Abhishek Das
• Reporter: Uma Maheswara Rao G
• Created: 01/May/20 01:52
• Updated: 10/Jun/21 07:56
• Resolved: 19/May/20 05:32

Description

As part of the design doc HDFS-15289, sanjay.radia and me discussed the following scenarios when fallback enabled.

Behavior when fallback enabled:

       Assume FS trees and mount mappings like below:

           mount link /a/b/c/d  → hdfs://nn1/a/b

           mount link /a/p/q/r  → hdfs://nn2/a/b    

           fallback → hdfs://nn3/  $  /a/c
                                                /x/z

1. Open(/x/y) then it goes to nn3 (fallback)      - WORKS
2. Create(/x/foo) then foo is created in nn3 in dir /x   - WORKS
3. ls /  should list   /a  /x .Today this does not work and IT IS A BUG!!! Because it conflicts with the open(/x/y)
4. Create /y  : fails  - also fails when not using  fallback  - WORKS
5. Create /a/z : fails - also fails when not using  fallback - WORKS
6. ls /a should list /b /p  as expected and will not show fallback in nn3 - WORKS

 

This Jira will fix issue of #3. So, when fallback enabled it should show merged ls view with mount links + fallback root. ( this will only be at root level)

Issue Links

• relates to: HDFS-15289 Allow viewfs mounts with HDFS/HCFS scheme and centralized mount table
• links to: GitHub Pull Request #2010