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From "Dave Moten (JIRA)" <j...@apache.org>
Subject [jira] [Created] (IO-528) Tailer.run race condition runaway logging
Date Wed, 01 Feb 2017 04:18:51 GMT
Dave Moten created IO-528:
-----------------------------

             Summary: Tailer.run race condition runaway logging
                 Key: IO-528
                 URL: https://issues.apache.org/jira/browse/IO-528
             Project: Commons IO
          Issue Type: Bug
          Components: Utilities
    Affects Versions: 2.5
            Reporter: Dave Moten


`Tailer.run` has a race condition that can have serious effects. 

The `run()` method has two while loops. The first waits till the file exists and the second
loop reads lines from the file doing some file rotation checking on the way.  If the file
is deleted while the second loop is in progress then the loop goes crazy logging warnings
that look like this:

`
Dec 06, 2016 1:02:18 AM com.github.davidmoten.logan.LogFile$1 fileRotated
INFO: file rotated
Dec 06, 2016 1:02:18 AM com.github.davidmoten.logan.LogFile$1 fileNotFound
WARNING: file not found
Dec 06, 2016 1:02:18 AM com.github.davidmoten.logan.LogFile$1 fileRotated
INFO: file rotated
Dec 06, 2016 1:02:18 AM com.github.davidmoten.logan.LogFile$1 fileNotFound
WARNING: file not found
Dec 06, 2016 1:02:18 AM com.github.davidmoten.logan.LogFile$1 fileRotated
INFO: file rotated
Dec 06, 2016 1:02:18 AM com.github.davidmoten.logan.LogFile$1 fileNotFound
WARNING: file not found
Dec 06, 2016 1:02:18 AM com.github.davidmoten.logan.LogFile$1 fileRotated
INFO: file rotated
Dec 06, 2016 1:02:18 AM com.github.davidmoten.logan.LogFile$1 fileNotFound
WARNING: file not found
`

In our case this had serious effects. The file being tailed was deleted by another process
and all available disk space was rapidly used up by the logging. This crashed a system.

The fix is to put a sleep after the call to `fileNotFound()`.

This problem was raised in IO-398 three years ago but no change was made to the code base.

PR submitted via github repo.



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