BIND 10 #1622: Ensure multiple processes log to same file when files are being rolled

[BIND 10 Development]

#1622: Ensure multiple processes log to same file when files are being rolled
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            Reporter:  stephen       |                        Owner:
                Type:  defect        |  jinmei
            Priority:  medium        |                       Status:
           Component:  logging       |  accepted
            Keywords:                |                    Milestone:
           Sensitive:  0             |  Sprint-20130611
         Sub-Project:  Core          |                   Resolution:
Estimated Difficulty:  6             |                 CVSS Scoring:
         Total Hours:  0             |              Defect Severity:
                                     |  Medium
                                     |  Feature Depending on Ticket:
                                     |          Add Hours to Ticket:  0
                                     |                    Internal?:  0
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Comment (by jinmei):

 trac1622 is ready for review.

 I've basically taken a minimalist approach: didn't introduce a derived
 class to solve this for log4cplus 1.0.x; didn't bother to leave
 warning log message when we detect it.  I explained why in the ticket
 comments.  Note that this should be relatively a rare problem in
 practice because normally logging should only happen sporadically and
 less frequently.

 Another note is that the log4cplus's internal log file is its default:
 "<log file name>.lock".  I considered an option of specifying our own
 name, but concluded the default should be better.  Note that this
 shouldn't cause permission problems we've seen with the in-house
 version of lock file; in fact, otherwise we couldn't even update the
 log file itself due to the permission problem.

 Proposed changelog entry:

 {{{
 622.?   [bug]           jinmei
         logging: prevented multiple BIND 10 processes from generating
         multiple small log files when they dumped logs to files and try
         to roll over them simultaneously.  This fix relies on a feature of
         underling logging library (log4cplus) version 1.1.0 or higher,
         so the problem can still happen if BIND 10 is built with an older
         version of log4cplus. (But this is expected to happen rarely in
         any case unless a verbose debug level is specified).
         (Trac #1622, git TBD)
 }}}

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Ticket URL: <http://bind10.isc.org/ticket/1622#comment:27>
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