Tailer erroneously consider file as new
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Key: IO-279
URL: https://issues.apache.org/jira/browse/IO-279
Project: Commons IO
Issue Type: Bug
Affects Versions: 2.0.1
Reporter: Sergio Bossa
Tailer sometimes erroneously consider the tailed file as new, forcing a
repositioning at the start of the file: I'm still unable to reproduce this in a
test case, because it only happens to me with huge log files during Apache
Tomcat startup.
This is the piece of code causing the problem:
// See if the file needs to be read again
if (length > position) {
// The file has more content than it did last time
last = System.currentTimeMillis();
position = readLines(reader);
} else if (FileUtils.isFileNewer(file, last)) {
/* This can happen if the file is truncated or overwritten
* with the exact same length of information. In cases like
* this, the file position needs to be reset
*/
position = 0;
reader.seek(position); // cannot be null here
// Now we can read new lines
last = System.currentTimeMillis();
position = readLines(reader);
}
What probably happens is that the new file content is about to be written on
disk, the date is already updated but content is still not flushed, so actual
length is untouched and there you go.
In other words, I think there should be some better method to verify the
condition above, rather than relying only on dates: keeping and comparing the
hash code of the latest line may be a solution, but may hurt performances ...
other ideas?
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