logrotateのファイル名に一意な値を入れたい ref: http://qiita.com/tbaba/items/76d8af798d1c138aaaf1

file0.txt

production.log
production.log.1
production.log.2
production.log.3

file1.txt

/var/www/app/shared/log/production.log {
  delaycompress
  compress
}

file2.txt

production.log
production.log.1
production.log.2.gz
production.log.3.gz

file3.txt

/var/www/app/shared/log/production.log {
  delaycompress
  compress
  dateext
}

file4.txt

production.log
production.log.2014-05-21
production.log.2014-05-20.gz
production.log.2014-05-19.gz