hadoop-common-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-5795) Add a bulk FIleSystem.getFileBlockLocations
Date Tue, 12 May 2009 13:35:45 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-5795?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12708433#action_12708433
] 

dhruba borthakur commented on HADOOP-5795:
------------------------------------------

Ok, so from what I can understand, here is the proposal:

Map<FileStatus, BlockLocation[]> listBlockLocations(Path[] inputPaths);

The "inputPaths" can be a set of files and/or directories. If one of the inputPaths is a directory,
then all items inside that directory (only one level, not recursive) are listed and their
block locations are returned by this call. if one of the inputPaths is a file, then its block
locations are returned by this call.  The FileStatus returned by this call should have the
absolulte path of the object being returned. 

> 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.


Mime
View raw message