liuxiaolong created HADOOP-16872:
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Summary: Performance improvement when distcp files in large dir
with -direct option
Key: HADOOP-16872
URL: https://issues.apache.org/jira/browse/HADOOP-16872
Project: Hadoop Common
Issue Type: Improvement
Reporter: liuxiaolong
We use distcp with -direct option to copy a file between two large directories.
We found it costed a few minutes. If we launch too much distcp jobs at the same
time, NameNode performance degradation is serious.
hadoop -direct -skipcrccheck -update -prbugaxt -i -numListstatusThreads 1
hdfs://cluster1:8020/source/100.log hdfs://cluster2:8020/target/100.jpg
|| ||Dir path||Count||
||Source dir|| hdfs://cluster1:8020/source/ ||100k+ files||
||Target dir||hdfs://cluster2:8020/target/ ||100k+ files||
Check code in CopyCommitter.java, we find in function
deleteAttemptTempFiles() has a code
targetFS.globStatus(new Path(targetWorkPath, ".distcp.tmp." +
jobId.replaceAll("job","attempt") + "*"));
it will waste a lot of time when distcp between two large dirs. When we use
distcp with -direct option, it will direct write to the target file without
generate a '.distcp.tmp' temp file. So, i think this code need add a judgment
in function deleteAttemptTempFiles, if distcp with -direct option, do nothing ,
directly return .
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