dog vdi check dead

[clicx]

I created 3 nodes cluster, cluster mode is zookeeper. And created some vdi, just do nothing and leaved them a few hours, then run the dog vdi check will dead.
I can see some errors in sheep.log, those machine are physically working fine:
Jun 10 15:42:58 ERROR [main] zk_create_seq_node(252) failed, path:/queue/, connection loss
Jun 10 15:42:58 ERROR [main] zk_get_data(265) failed, path:/queue/0000000043, session expired
Jun 10 15:42:58 ERROR [main] zk_find_seq_node(505) failed, session expired
Jun 10 15:42:58 ERROR [main] zk_queue_push(536) failed, path:/queue/, connection loss
Jun 10 15:42:58 ERROR [main] add_event(698) failed, type: 3, connection loss
Jun 10 15:42:58 ERROR [main] zk_create_seq_node(252) failed, path:/queue/, invalid zhandle state
Jun 10 15:42:58 ERROR [main] zk_queue_push(536) failed, path:/queue/, invalid zhandle state
Jun 10 15:42:58 ERROR [main] add_event(698) failed, type: 3, invalid zhandle state
Jun 10 15:42:58 ERROR [main] zk_create_seq_node(252) failed, path:/queue/, invalid zhandle state
Jun 10 15:42:58 ERROR [main] zk_queue_push(536) failed, path:/queue/, invalid zhandle state
Jun 10 15:42:58 ERROR [main] add_event(698) failed, type: 3, invalid zhandle state
Jun 10 15:42:58 ERROR [main] zk_event_handler(1297) detect a session timeout. reconnecting...
Jun 10 15:42:58 INFO [main] zk_init(1498) version 3.4.9, address node1:2181,node2:2181,node3:2181/sheepdog, timeout 30000