'Launches all EC2 instances based on this cluster\'s settings.'

def create_cluster(self):

    log.info(('Launching    a    %d-node    %s' % (self.cluster_size, '    '.join([('VPC' if self.subnet_id else ''), 'cluster...']).strip())))
    mtype = (self.master_instance_type or self.node_instance_type)
    self.master_instance_type = mtype
    if self.spot_bid:
        self._create_spot_cluster()
    else:
        self._create_flat_rate_cluster()
