def prune_dead_workers
      Worker.all.each do |worker|
        host, pid, thread, path, queues = worker.id.split(':')
        next unless host.include?(hostname)
        next if worker_pids.include?(pid)
        log! "Pruning dead worker: #{worker}"
        worker.unregister_worker
      end
    end
def prune_dead_workers
      Worker.all.each do |worker|
        host, pid, thread, path, queues = worker.id.split(':')
        next unless host.include?(hostname)
        next if worker_pids.include?(pid)
        log! "Pruning dead worker: #{worker}"
        worker.unregister_worker
      end
    end
Looks for any workers which should be running on this server
 and, if they're not, removes them from Redis.

 This is a form of garbage collection. If a server is killed by a
 hard shutdown, power failure, or something else beyond our
 control, the Resque workers will not die gracefully and therefore
 will leave stale state information in Redis.

 By checking the current Redis state against the actual
 environment, we can determine if Redis is old and clean it up a bit.