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Posted to mapreduce-issues@hadoop.apache.org by "Steve Loughran (Jira)" <ji...@apache.org> on 2019/09/17 10:57:00 UTC
[jira] [Commented] (MAPREDUCE-7241) FileInputFormat listStatus
causes oom when there are lots of files
[ https://issues.apache.org/jira/browse/MAPREDUCE-7241?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16931306#comment-16931306 ]
Steve Loughran commented on MAPREDUCE-7241:
-------------------------------------------
I see: HdfsBlockLocation includes too much information which causes the OOM problems.
At a quick scan of the code through the IDE, I don't see that extra block location info being used outside of tests.
Maybe the thing to do here is (somehow) not collect that information in the DFS listLocatedStatus call?
> FileInputFormat listStatus causes oom when there are lots of files
> ------------------------------------------------------------------
>
> Key: MAPREDUCE-7241
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-7241
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: job submission
> Affects Versions: 2.6.1
> Reporter: Zhihua Deng
> Priority: Major
> Attachments: filestatus.png
>
>
> This case sometimes sees in hive when user issues queries over all partitions by mistakes. The file status cached when listing status could accumulate to over 3g. After digging into the dumped memory, the LocatedBlock occupies about 50%(sometimes over 60%) memory that retained by LocatedFileStatus, as shows followed,
> !filestatus.png!
> Right now we only extract the block locations info from LocatedFileStatus, the datanode infos(types) or block token are not taken into account. So there is no need to cache LocatedBlock, as do like this:
> BlockLocation[] blockLocations = dedup(stat.getBlockLocations());
> LocatedFileStatus shrink = new LocatedFileStatus(stat, blockLocations);
> private static BlockLocation[] dedup(BlockLocation[] blockLocations) {
> BlockLocation[] copyLocs = new BlockLocation[blockLocations.length];
> int i = 0;
> for (BlockLocation location : blockLocations)
> { copyLocs[i++] = new BlockLocation(location); }
> return copyLocs;
> }
>
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