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Sanjay Radia commented on HDFS-202: ----------------------------------- > Maybe we should punt that until someone develops an append-savvy distcp? +1 >Why is DetailedFileStatus[] better than Map<FileStatus,BlockLocation[]>? The >latter seems more transparent. I was holding out on a file system interface return a map. But that is old school. Fine I am convinced. I suspect you also want the rpc signature to return a map (that makes me more nervous because most rpcs do not support that - but ours does I guess.). ----- Wrt to the new FileContext api, my proposal is that its provides a single getBlockLocation method: Map<FileStatus,BlockLocation[]> getBlockLocations(Path[] path) and abandon the BlockLocation[] getBlockLocations(path, start, end). (of course FileSystem will continue to support the old getBlockLocations.) > Add a bulk FIleSystem.getFileBlockLocations > ------------------------------------------- > > Key: HDFS-202 > URL: https://issues.apache.org/jira/browse/HDFS-202 > Project: Hadoop HDFS > Issue Type: New Feature > Reporter: Arun C Murthy > Assignee: Jakob Homan > > Currently map-reduce applications (specifically file-based input-formats) use > FileSystem.getFileBlockLocations to compute splits. However they are forced > to call it once per file. > The downsides are multiple: > # Even with a few thousand files to process the number of RPCs quickly > starts getting noticeable > # The current implementation of getFileBlockLocations is too slow since > each call results in 'search' in the namesystem. Assuming a few thousand > input files it results in that many RPCs and 'searches'. > It would be nice to have a FileSystem.getFileBlockLocations which can take in > a directory, and return the block-locations for all files in that directory. > We could eliminate both the per-file RPC and also the 'search' by a 'scan'. > When I tested this for terasort, a moderate job with 8000 input files the > runtime halved from the current 8s to 4s. Clearly this is much more important > for latency-sensitive applications... -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.