[HADOOP-14136] Default FS For ViewFS

• Type: New Feature
• Status: Resolved
• Priority: Major
• Resolution: Duplicate
• Fix Version/s: 3.0.0
• Component/s: fs, viewfs
• Target Version/s: 3.0.0
• Assignee: Manoj Govindassamy
• Reporter: Erik Krogen
• Created: 01/Mar/17 19:01
• Updated: 25/Oct/17 19:02
• Resolved: 25/Oct/17 19:02

Description

It would be useful if ViewFS had the ability to designate one FileSystem as a "primary"/"default" to fall back to in the case that an entry in the mount table is not found. Consider the situation when you have a mount table that looks like:

/data -> hdfs://nn1/data
/logs -> hdfs://nn1/logs
/user -> hdfs://nn1/user
/remote -> hdfs://nn2/remote

nn1 here is being used as the primary, with a specific directory 'remote' being offloaded to another namenode. This works, but if we want to add another top-level directory to nn1, we have to update all of our client-side mount tables. Merge links (HADOOP-8298) could be used to achieve this but they do not seem to be coming soon; this special case of a default FS is much simpler - try to resolve through the VFS mount table, if not found, then resolve to the defaultFS.

There is a good discussion of this at https://issues.apache.org/jira/browse/HADOOP-13055?focusedCommentId=15733822&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-15733822

Issue Links

• duplicates: HADOOP-13055 Implement linkMergeSlash and linkFallback for ViewFileSystem
• is related to: HADOOP-8299 ViewFileSystem link slash mount point crashes with IndexOutOfBoundsException
• is related to: HADOOP-13055 Implement linkMergeSlash and linkFallback for ViewFileSystem