after zk session timeout, watchers/ehpemeral nodes are lost
after zk session timeout, watchers/ehpemeral nodes are lost

TODO: if we want to keep the server running, we MUST rebuild the
zk watchers and ephemeral nodes

funkygao/gafka,funkygao/gafka,funkygao/gafka,funkygao/gafka,funkygao/gafka