sfc classifier flows deleted during ovs-agent restart

[root@EXTENV-10-254-9-82 ~]# openstack sfc flow classifier list
+--------------------------------------+------+----------+-----------+-------------------+--------------------------------------+--------------------------+
| ID | Name | Protocol | Source-IP | Destination-IP | Logical-Source-Port | Logical-Destination-Port |
+--------------------------------------+------+----------+-----------+-------------------+--------------------------------------+--------------------------+
| 56933578-1384-47d8-ac0f-945917590387 | | tcp | None | 192.168.100.10/32 | 1d058e59-2ea8-4f02-8f5e-3b81b8b9306b | None |
+--------------------------------------+------+----------+-----------+-------------------+--------------------------------------+--------------------------+
[root@EXTENV-10-254-9-82 ~]# openstack port show 1d058e59-2ea8-4f02-8f5e-3b81b8b9306b
+-----------------------+------------------------------------------------------------------------------+
| Field | Value |
+-----------------------+------------------------------------------------------------------------------+
| admin_state_up | UP |
| allowed_address_pairs | |
| binding_host_id | EXTENV-10-254-8-14 |
| binding_profile | |
| binding_vif_details | ovs_hybrid_plug='True', port_filter='True' |
| binding_vif_type | ovs |
| binding_vnic_type | normal |
| created_at | 2017-04-26T02:19:27Z |
| description | |
| device_id | d9d5f523-a402-4019-b490-b4d68d65c06d |
| device_owner | network:router_interface |
| dns_assignment | None |
| dns_name | None |
| extra_dhcp_opts | |
| fixed_ips | ip_address='192.168.100.1', subnet_id='14590ffd-2313-4cbf-aeed-dc522acb69ae' |
| id | 1d058e59-2ea8-4f02-8f5e-3b81b8b9306b |
| ip_address | None |
| mac_address | fa:16:3e:e4:18:86 |
| name | |
| network_id | f15412d7-4aad-498e-ad44-275be87a5681 |
| option_name | None |
| option_value | None |
| port_security_enabled | False |
| project_id | d8cdc97536a545e4a135a9505665f87e |
| qos_policy_id | None |
| revision_number | 86 |
| security_groups | |
| status | ACTIVE |
| subnet_id | None |
| updated_at | 2017-04-28T03:54:11Z |
+-----------------------+------------------------------------------------------------------------------+
[root@EXTENV-10-254-9-82 ~]#

During ovs-agent restarting, i can fetch the classifier flows:

[root@EXTENV-10-254-8-14 agent]# ovs-ofctl dump-flows br-int |grep group
 cookie=0xa4175c3a6393f0ba, duration=113.411s, table=0, n_packets=0, n_bytes=0, idle_age=113, priority=30,tcp,in_port=7539,nw_dst=192.168.100.10,tp_dst=0x1f40/0xffc0 actions=group:1
 cookie=0xa4175c3a6393f0ba, duration=113.398s, table=0, n_packets=0, n_bytes=0, idle_age=113, priority=30,tcp,in_port=7539,nw_dst=192.168.100.10,tp_dst=0x1f80/0xff80 actions=group:1
 cookie=0xa4175c3a6393f0ba, duration=113.387s, table=0, n_packets=0, n_bytes=0, idle_age=113, priority=30,tcp,in_port=7539,nw_dst=192.168.100.10,tp_dst=0x2000/0xfe00 actions=group:1
 cookie=0xa4175c3a6393f0ba, duration=113.375s, table=0, n_packets=0, n_bytes=0, idle_age=113, priority=30,tcp,in_port=7539,nw_dst=192.168.100.10,tp_dst=0x2200/0xff00 actions=group:1
 cookie=0xa4175c3a6393f0ba, duration=113.362s, table=0, n_packets=0, n_bytes=0, idle_age=113, priority=30,tcp,in_port=7539,nw_dst=192.168.100.10,tp_dst=0x2300/0xffe0 actions=group:1
 cookie=0xa4175c3a6393f0ba, duration=113.350s, table=0, n_packets=0, n_bytes=0, idle_age=113, priority=30,tcp,in_port=7539,nw_dst=192.168.100.10,tp_dst=0x2320/0xfff8 actions=group:1
 cookie=0xa4175c3a6393f0ba, duration=113.339s, table=0, n_packets=0, n_bytes=0, idle_age=113, priority=30,tcp,in_port=7539,nw_dst=192.168.100.10,tp_dst=9000 actions=group:1
[root@EXTENV-10-254-8-14 agent]#

But after restarting is finished, i got nothing:
[root@EXTENV-10-254-8-14 agent]# ovs-ofctl dump-flows br-int |grep group
[root@EXTENV-10-254-8-14 agent]#