[HDFS-11221] Have StorageDirectory return Optional<File> instead of File/null

• Type: Task
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Assignee: Jiajia Li
• Reporter: Ewan Higgs
• Created: 07/Dec/16 21:26
• Updated: 17/Mar/17 00:26

Description

In HDFS-10675, StorageDirectory.root can be null because PROVIDED storage locations will not have any directories associated with them. Hence, we need to add checks to StorageDirectory to make sure we handle this. This would also lead to changes in code that call StorageDirectory.getRoot, StorageDirectory.getCurrentDir, StorageDirectory.getVersionFile etc. as the return value can be nul}}l (if {{StorageDirectory.root is null).

The proposal to handle this is to change the return type of the above functions to Optional<File>. According to my preliminary check, this will result in changes in ~70 places, which is why it's not appropriate to put it in the patch for HDFS-10675. But it is certainly a valuable fix.

Issue Links

• is related to: HDFS-10675 [READ] Datanode support to read from external stores.