Steve Loughran created HADOOP-13884:
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             Summary: s3a create(overwrite=true) to only look for dir/ and list 
entries, not file
                 Key: HADOOP-13884
                 URL: https://issues.apache.org/jira/browse/HADOOP-13884
             Project: Hadoop Common
          Issue Type: Sub-task
          Components: fs/s3
    Affects Versions: 2.9.0
            Reporter: Steve Loughran
            Priority: Minor


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 to 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



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