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Posted to mapreduce-issues@hadoop.apache.org by "Arun Suresh (JIRA)" <ji...@apache.org> on 2018/06/12 23:13:00 UTC
[jira] [Updated] (MAPREDUCE-7101) Add config parameter to allow JHS
to alway scan user dir irrespective of modTime
[ https://issues.apache.org/jira/browse/MAPREDUCE-7101?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Arun Suresh updated MAPREDUCE-7101:
-----------------------------------
Summary: Add config parameter to allow JHS to alway scan user dir irrespective of modTime (was: Revisit behavior of JHS scan file behavior)
> Add config parameter to allow JHS to alway scan user dir irrespective of modTime
> --------------------------------------------------------------------------------
>
> Key: MAPREDUCE-7101
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-7101
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Reporter: Wangda Tan
> Assignee: Thomas Marquardt
> Priority: Critical
> Attachments: MAPREDUCE-7101.001.patch, MAPREDUCE-7101.001.patch
>
>
> Currently, the JHS scan directory if the modification of *directory* changed:
> {code}
> public synchronized void scanIfNeeded(FileStatus fs) {
> long newModTime = fs.getModificationTime();
> if (modTime != newModTime) {
> <... omitted some logics ...>
> // reset scanTime before scanning happens
> scanTime = System.currentTimeMillis();
> Path p = fs.getPath();
> try {
> scanIntermediateDirectory(p);
> {code}
> This logic relies on an assumption that, the directory's modification time will be updated if a file got placed under the directory.
> However, the semantic of directory's modification time is not consistent in different FS implementations. For example, MAPREDUCE-6680 fixed some issues of truncated modification time. And HADOOP-12837 mentioned on S3, the directory's modification time is always 0.
> I think we need to revisit behavior of this logic to make it to more robustly work on different file systems.
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