[jira] [Created] (IO-591) Tailer has issue if a file is not logged to after rotating the file and second rotation occurs.

["chris humphrey (JIRA)" <ji...@apache.org>]

chris humphrey created IO-591:
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             Summary: Tailer has issue if a file is not logged to after rotating the file and second rotation occurs.
                 Key: IO-591
                 URL: https://issues.apache.org/jira/browse/IO-591
             Project: Commons IO
          Issue Type: Bug
            Reporter: chris humphrey


We are using the org.apache.commons.io.input.Tailer for scrapping logs as another system generates the logs.  Generally, our logs will rotate at midnight each night, sometimes no data will be sent to a log file for more than a day, this is where the problem comes in.

If the Tailer is working on a file and it is rotated, everything works fine unless the file is not written to before the next rotation.  Looking at Tailer.java beginning at line 457, there is a conditional "if (length > position)"... "else if (newer) {"

anytime the code gets into the "else if (newer) {" block is when this issue will occur.

The issue was noticed in a second hand way, and commented in the file

/* ... This can happen if the file is truncated or overwritten... */

So, in this block, the file has been Rotated, but, there is no place in this block where the RandomAccessFile is re-created with the 'new' underlying file. 

Anything written into the new file will be noticed because above, the File is used, but, when the code attempts to read from the file, it will never get the data written.

There are multiple ways to fix this, one work around is to set reOpen to true.  Unfortunately, this is not a good workaround for us as the files we are scraping can get very large, seeking to large files every 500ms is not a great way for our production servers to spend their time.

 

The real fix is to rebuild the RandomAccessFile as it is done beginning on line 437 of the same file.  

 

I can make changes and propose them but have never submitted changes for Apache open source and would need some guidance on the process.

 

 



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