[HADOOP-13884] s3a create(overwrite=true) to only look for dir/ and list entries, not file

• Type: Sub-task
• Status: Resolved
• Priority: Minor
• Resolution: Duplicate
• Affects Version/s: 2.9.0
• Fix Version/s: 3.3.0
• Component/s: fs/s3
• Target Version/s: 3.3.0
• Assignee: Steve Loughran
• Reporter: Steve Loughran
• Created: 09/Dec/16 13:20
• Updated: 11/Sep/19 16:01
• Resolved: 11/Sep/19 16:01

Description

before doing a create(), s3a does a getFileStatus() to make sure there isn't a directory there, and, if overwrite=false, that there isn't a file.

Because S3 caches negative HEAD/GET requests, if there isn't a file, then even after the PUT, a later GET/HEAD may return 404; we are generating create consistency where none need exist.

when overwrite=true we don't care whether the file exists or not, only that the path isn't a directory. So we can just do the HEAD path +"/' and the LIST calls, skipping the HEAD path. This will save an HTTP round trip of a few hundred millis, and ensure that there's no 404 cached in the S3 front end for later callers

Issue Links

• Is contained by: HADOOP-16490 Avoid/handle cached 404s during S3A file creation
• is duplicated by: HADOOP-13950 S3A create(path, overwrite=true) need only check for path being a dir, not a file
• is related to: HADOOP-13430 Optimize getFileStatus in S3A