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From "Sebb (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (IO-398) listener.fileRotated() will be invoked more than one time in a real rotate activity
Date Fri, 13 Sep 2013 16:50:53 GMT

    [ https://issues.apache.org/jira/browse/IO-398?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13766626#comment-13766626
] 

Sebb commented on IO-398:
-------------------------

On Windows when the Tailer has the file open for read, it's not possible to delete the file.
I've not tested (yet), but I don't think it's possible to rename the file either. The locking
issue is why the reOpen option was added.

Your unit test requires the file to be deleted/renamed. On Windows this can only be done whilst
the Tailer is sleeping.
When it wakes up, it throws FileNotFoundException and stops processing. So it's not possible
to run the unit test on Windows.

But it's not only on Windows that this behaviour will occur. If the Tailer is set to reOpen,
the same can happen on Un*x.
Try it and see (I assume you are not testing on Windows).

So I think we need to fix the reOpen behaviour first, and then this bug can be addressed.
                
> listener.fileRotated() will be invoked more than one time in a real rotate activity
> -----------------------------------------------------------------------------------
>
>                 Key: IO-398
>                 URL: https://issues.apache.org/jira/browse/IO-398
>             Project: Commons IO
>          Issue Type: Bug
>    Affects Versions: 2.4
>            Reporter: Lantao Jin
>         Attachments: IO-398.patch, IO398_with_ut.patch
>
>
>        When Tailer considers file rotation is occurred, listener.fileRotated() will be
execute, and file will re-open by "reader = new RandomAccessFile(file, RAF_MODE);". However,
the new file may not be created yet, FileNotFoundException would be caught and while loop
would be executed again and again until the new file is actually created, which cause listener.fileRotated()
triggered repeatedly. 
> This is the piece of code causing the problem:
> {noformat} 
> while (getRun()) {
>     final boolean newer = isFileNewer(file, last); // IO-279, must be done first
>     // Check the file length to see if it was rotated
>     final long length = file.length();
>     if (length < position) {
>         // File was rotated
>         listener.fileRotated();
>         // Reopen the reader after rotation
>         try {
>             // Ensure that the old file is closed iff we re-open it successfully
>             final RandomAccessFile save = reader;
>             reader = new RandomAccessFile(file, RAF_MODE);
>             /* some code */
>         } catch (final FileNotFoundException e) {
>             // in this case we continue to use the previous reader and position values
>             listener.fileNotFound();
>         }
>         continue;
> {noformat}
>       While condition checkes can be deployed in listener.fileRotated() to correct the
sematic of fileRotate, it is better to prevent multiple invocation of listener.fileRotated()
on this issue.

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