[
https://issues.apache.org/jira/browse/IO-279?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13633820#comment-13633820
]
Herman Meerlo commented on IO-279:
----------------------------------
Well, this is the world turned upside down. I can only reopen the issue if I
have a patch for it. That doesn't make sense. The problem still exists and
therefore the ticket should be reopened. I have patched it locally for myself
but I doubt that my patch is ok for everyone because I completely removed the
last else if statement. For me it makes no sense to check if the file is newer.
The only use case would be that the file had been overwritten with exactly the
same amount of data. Truncation is not an issue because that would mean that
the length and position must have been 0 anyway. For me it is way more likely
that the file's modified time has been updated than that the content has been
overwritten with the same amount of bytes.
> Tailer erroneously considers file as new
> ----------------------------------------
>
> 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
> Fix For: 2.4
>
> Attachments: IO-279.patch
>
>
> Tailer sometimes erroneously considers 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:
> {code}
> // 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);
> }
> {code}
> 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?
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira
