Steve Loughran created HADOOP-17833:
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             Summary: createFile() under a magic path to skip all probes for 
file/dir at end of path
                 Key: HADOOP-17833
                 URL: https://issues.apache.org/jira/browse/HADOOP-17833
             Project: Hadoop Common
          Issue Type: Improvement
          Components: fs/s3
    Affects Versions: 3.3.1
            Reporter: Steve Loughran


Magic committer tasks can be slow because every file created with 
overwrite=false triggers a HEAD (verify there's no file) and a LIST (that 
there's no dir). And because of delayed manifestations, it may not behave as 
expected.

ParquetOutputFormat is one example of a library which does this.

we could fix parquet to use overwrite=true, but (a) there may be surprises in 
other uses (b) it'd still leave the list and (c) do nothing for other formats 
call

Proposed: createFile() under a magic path to skip all probes for file/dir at 
end of path

Only a single task attempt Will be writing to that directory and it should know 
what it is doing. If there is conflicting file names and parts across tasks 
that won't even get picked up at this point. Oh and none of the committers ever 
check for this: you'll get the last file manifested (s3a) or renamed (file)

If we skip the checks we will save 2 HTTP requests/file.




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