title: logger creating multiple files
body: <p>The following piece of code creates 3 or 4 log files.  How should it be written so that only 1 file is created while keeping the format of the filename?  Also, this seems to be a Windows only issue.  When I run this on a RHEL 5.3 box even setting nproc to 1000, I only get 1 log file.  [Python 3.4.1]</p>
  
  <pre><code>import datetime, logging, multiprocessing, os.path, time
  
  logging.basicConfig(level=logging.DEBUG, format="%(asctime)-4s %(process)6s  %(message)s", datefmt="%m-%d %H:%M:%S",
      filename="test_%s.log"%(datetime.datetime.today().strftime("%Y%m%d-%H%M%S")))
  
  def worker(n):
      logging.info("before")
      time.sleep(n)
      logging.info("after")
  
  if __name__=='__main__':
      nproc = 40
      pool = multiprocessing.Pool(processes=nproc)
      pool.map(worker, (6,)*nproc)
  </code></pre>