func (c *C) CoordinatorIsDown(group string) {
log.Warnf("coordinator (%s) is down", group)
c.pool.DeleteCoordinator(group)
}
func (c *C) LeaderIsDown(topic string, partition int32) {
log.Warnf("leader (%s,%d) is down", topic, partition)
c.pool.DeleteLeader(topic, partition)
}