unicorn.conf

/path/to/unicorn/log/unicorn.stderr.log
/path/to/production/log/production.log 
{
  daily
  missingok
  rotate 180
  compress
  dateext

  # this is important if using "compress" since we need to call
  # the "lastaction" script below before compressing:
  delaycompress

  # note the lack of the evil "copytruncate" option in this
  # config.  Unicorn supports the USR1 signal and we send it
  # as our "lastaction" action:
  lastaction
    pid=/path/to/pid/unicorn.pid
    test -s $pid && kill -USR1 "$(cat $pid)"
  endscript
}