[jira] [Created] (HADOOP-15489) S3Guard to self update on directory listings of S3

["Steve Loughran (JIRA)" <ji...@apache.org>]

Steve Loughran created HADOOP-15489:
---------------------------------------

             Summary: S3Guard to self update on directory listings of S3
                 Key: HADOOP-15489
                 URL: https://issues.apache.org/jira/browse/HADOOP-15489
             Project: Hadoop Common
          Issue Type: Sub-task
          Components: fs/s3
    Affects Versions: 3.1.0
         Environment: s3guard
            Reporter: Steve Loughran


S3Guard updates its table on a getFileStatus call, but not on a directory listing.

While this makes directory listings faster (no need to push out an update), it slows down subsequent queries of the files, such as a sequence of:

{code}
statuses = s3a.listFiles(dir)
for (status: statuses) {
  if (status.isFile) {
      try(is = s3a.open(status.getPath())) {
        ... do something
      }
}
{code}

this is because the open() is doing the getFileStatus check, even after the listing.

Updating the DDB tables after a listing would give those reads a speedup, albeit at the expense of initiating a (bulk) update in the list call. Of course, we could consider making that async, though that design (essentially a write-buffer) would require the buffer to be checked in the reads too. 



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