Sandy Ryza created MAPREDUCE-4907:
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Summary: TrackerDistributedCacheManager issues too many
getFileStatus calls
Key: MAPREDUCE-4907
URL: https://issues.apache.org/jira/browse/MAPREDUCE-4907
Project: Hadoop Map/Reduce
Issue Type: Bug
Components: mrv1, tasktracker
Affects Versions: 1.1.1
Reporter: Sandy Ryza
Assignee: Sandy Ryza
TrackerDistributedCacheManager issues a number of redundant getFileStatus calls
when determining the timestamps and visibilities of files in the distributed
cache. 300 distributed cache files deep in the directory structure can hammer
HDFS with a couple thousand requests.
A couple optimizations can reduce this load:
1. determineTimestamps and determineCacheVisibilities both call getFileStatus
on every file. We could cache the results of the former and use them for the
latter.
2. determineCacheVisibilities needs to check that all ancestor directories of
each file have execute permissions for everyone. This currently entails a
getFileStatus on each ancestor directory for each file. The results of these
getFileStatus calls could be cached as well.
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