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Konstantin Shvachko commented on HADOOP-5795: --------------------------------------------- > (non-recursively?) I think the rpc call itself should not be recursive. It is like with ls: the getListing() call is non-recursive, but the client recursively calls getListing() on sub-directories. The idea is to prevent people from making a mistake to call getBlockLocation("/") on large directory trees recursively, which may freeze the name-node for a long period of time. Non-recursive variant should be sufficient to cover Arun's use case. > Add a bulk FIleSystem.getFileBlockLocations > ------------------------------------------- > > Key: HADOOP-5795 > URL: https://issues.apache.org/jira/browse/HADOOP-5795 > Project: Hadoop Core > Issue Type: New Feature > Components: dfs > Affects Versions: 0.20.0 > Reporter: Arun C Murthy > Assignee: Jakob Homan > Fix For: 0.21.0 > > > 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.