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Posted to mapreduce-issues@hadoop.apache.org by "Zhihua Deng (Jira)" <ji...@apache.org> on 2019/09/18 03:00:00 UTC
[jira] [Commented] (MAPREDUCE-7241) FileInputFormat listStatus
causes oom when there are lots of files in HDFS
[ https://issues.apache.org/jira/browse/MAPREDUCE-7241?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16931994#comment-16931994 ]
Zhihua Deng commented on MAPREDUCE-7241:
----------------------------------------
Changing listLocatedStatus like that is hard to debug. [~stevel@apache.org], can we do a copy here when listing status? as new BlockLocation(location) will the remove LocatedBlock info from the _location_ instance, this seemed to be the most easy way
> FileInputFormat listStatus causes oom when there are lots of files in HDFS
> --------------------------------------------------------------------------
>
> 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[] dup(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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