BIND 10 #1071: introduce "null" output for logs

[BIND 10 Development]

#1071: introduce "null" output for logs
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            Reporter:  jinmei        |                        Owner:
                Type:  task          |                       Status:  new
            Priority:  major         |                    Milestone:
           Component:  logging       |  Sprint-20110712
           Sensitive:  0             |                     Keywords:
         Sub-Project:  DNS           |              Defect Severity:  N/A
Estimated Difficulty:  0             |  Feature Depending on Ticket:
         Total Hours:  0             |          Add Hours to Ticket:  0
                                     |                    Internal?:  0
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 We need a special type of logging output (say "null") in addition to
 more common syslog, local log file, stdout/stderr.  If it's specified
 as the logging output, log messages will be generated but won't actually
 appear anywhere.

 If you are familiar with BIND 9, it's like BIND 9's "null" logging
 channel.

 The primary purpose for this feature is to help #1024: so that we
 won't spam test outputs due to the verbose log messages (note that
 even without #1024, some log messages are currently dumped to
 test outputs.  So if we care about noise in test outputs, this feature
 is useful anyway).

 As agreed on jabber, I'm pushing this to the current sprint.

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Ticket URL: <http://bind10.isc.org/ticket/1071>
BIND 10 Development <http://bind10.isc.org>
BIND 10 Development