Wangda Tan created MAPREDUCE-7101:
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Summary: Revisit behavior of JHS scan file behavior
Key: MAPREDUCE-7101
URL: https://issues.apache.org/jira/browse/MAPREDUCE-7101
Project: Hadoop Map/Reduce
Issue Type: Bug
Reporter: Wangda Tan
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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