作者：张华 发表于：2022-08-25
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问题
客户描述虚机的metadata功能偶尔有问题，他们怀疑是：https://bugs.launchpad.net/networking-ovn/+bug/1953591
客户还说出现问题之后在出现问题的虚机所在的host上重启neutron-ovn-metadata-agent服务可以恢复服务，重启这个服务会重新运行：
/usr/bin/neutron-rootwrap /etc/neutron/rootwrap.conf ip netns exec ovnmeta-63e2c276-60dd-40e3-baa1-c16342eacce2 haproxy -f /var/lib/neutron/ovn-metadata-proxy/63e2c276-60dd-40e3-baa1-c16342eacce2.conf
ovn metadata原理
我很熟悉neutron metadata, 但ovn metadata弄得还是很多，但它们的原理应该是类似的．
- 对于sriov port它会有一个对应的external port来提供ovn metadata功能，所以ovn medata是在GW chassis上做的，与compute chassis并不在同一节点．流程见：20220607 - sriov ovn metadata - https://blog.csdn.net/quqi99/article/details/116893909 ,
- 对于普通虚机的metadata是由它所在的compute chassis上的ovnmeta-xxx来做．
1, 虚机VM(192.168.21.75)内可以由dhcp(192.168.21.2)提供主机路由来直接转发到元数据代理neutron-ovn-metadata-agent(192.168.21.2), 若没有启用dhcp则由GW转发至neutron-ovn-metadata-agent
$ ssh -i ~/testkey.priv ubuntu@10.5.150.219 -- ip route list |grep 169
169.254.169.254 via 192.168.21.2 dev ens2 proto dhcp src 192.168.21.75 metric 100
$ openstack port list
+--------------------------------------+------+-------------------+------------------------------------------------------------------------------+--------+
| ID | Name | MAC Address | Fixed IP Addresses | Status |
+--------------------------------------+------+-------------------+------------------------------------------------------------------------------+--------+
| 48244606-524d-4c24-bc54-0143869d4267 | | fa:16:3e:43:81:23 | ip_address='192.168.21.2', subnet_id='7a3260aa-e2a6-4721-8f0a-5b06aec71b53' | DOWN |
| 5043ab8b-184d-4d83-abf8-fa044aec9a6d | | fa:16:3e:e2:8c:a0 | ip_address='10.5.152.84', subnet_id='a0f40836-715c-4dcc-9df1-fb4093aa0f79' | DOWN |
| 544e4423-d3d8-418e-8b6c-ea294ff0d1b3 | | fa:16:3e:a2:83:76 | | DOWN |
| 70b96954-32a2-488b-b67b-4bf039189b02 | | fa:16:3e:42:29:d4 | ip_address='192.168.21.1', subnet_id='7a3260aa-e2a6-4721-8f0a-5b06aec71b53' | ACTIVE |
| c99885ae-1778-46cb-af07-29cf32113ef7 | | fa:16:3e:4d:03:e6 | ip_address='10.5.150.219', subnet_id='a0f40836-715c-4dcc-9df1-fb4093aa0f79' | N/A |
| dd6bd055-3460-459e-b9b2-8da7211dacdc | | fa:16:3e:53:b7:77 | ip_address='192.168.21.75', subnet_id='7a3260aa-e2a6-4721-8f0a-5b06aec71b53' | ACTIVE |
+--------------------------------------+------+-------------------+------------------------------------------------------------------------------+--------+
2, 计算节点上运行一个neutron-ovn-metadata-agent, 同时neutron-ovn-metadata-agent为每个network创建一个ovnmeta-xxx并启动haproxy实例.
如果ovn-meta-xxx不存在就会被创建一个，并且使用veth pair将ovn-meta-xxx(eg:tap8ea7d54e-51)与host(eg:tap8ea7d54e-50, 再加到br-int)相连.
haproxy实例监听169.254.169.254:80，并加入X-OVN-Network-ID头，最后转到backend (unix socket: /var/lib/neutron/metadata_proxy)
#nova-compute/0 has 3 processes about metadata
/usr/bin/python3 /usr/bin/neutron-ovn-metadata-agent --config-file=/etc/neutron/neutron.conf --config-file=/etc/neutron/neutron_ovn_metadata_agent.ini --log-file=/var/log/neutron/neutron-ovn-metadata-agent.log
/usr/bin/python3 /usr/bin/nova-api-metadata --config-file=/etc/nova/nova.conf --log-file=/var/log/nova/nova-api-metadata.log
haproxy -f /var/lib/neutron/ovn-metadata-proxy/8ea7d54e-5fe0-408d-9de8-5ccbed8ede84.conf
$ sudo ip netns exec ovnmeta-8ea7d54e-5fe0-408d-9de8-5ccbed8ede84 ip addr show tap8ea7d54e-51 |grep -E 'link|inet'
link/ether fa:16:3e:43:81:23 brd ff:ff:ff:ff:ff:ff link-netnsid 0
inet 169.254.169.254/32 brd 169.254.169.254 scope global tap8ea7d54e-51
inet 192.168.21.2/24 brd 192.168.21.255 scope global tap8ea7d54e-51
$ ip addr show tap8ea7d54e-50 |grep link
link/ether ca:cb:5c:af:dd:22 brd ff:ff:ff:ff:ff:ff link-netns ovnmeta-8ea7d54e-5fe0-408d-9de8-5ccbed8ede84
$ sudo ovs-vsctl show |grep 8ea7d54e
Port tap8ea7d54e-50
Interface tap8ea7d54e-50
$ sudo ip netns exec ovnmeta-8ea7d54e-5fe0-408d-9de8-5ccbed8ede84 route -n
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.21.0 0.0.0.0 255.255.255.0 U 0 0 0 tap8ea7d54e-51
$ cat /var/lib/neutron/ovn-metadata-proxy/8ea7d54e-5fe0-408d-9de8-5ccbed8ede84.conf
global
log /dev/log local0 info
user root
group root
maxconn 1024
pidfile /var/lib/neutron/external/pids/8ea7d54e-5fe0-408d-9de8-5ccbed8ede84.pid.haproxy
daemon
defaults
log global
mode http
option httplog
option dontlognull
option http-server-close
option forwardfor
retries 3
timeout http-request 30s
timeout connect 30s
timeout client 32s
timeout server 32s
timeout http-keep-alive 30s
listen listener
bind 169.254.169.254:80
server metadata /var/lib/neutron/metadata_proxy
http-request add-header X-OVN-Network-ID 8ea7d54e-5fe0-408d-9de8-5ccbed8ede84
3, neutron-ovn-metadata-agent与unix socket（/var/lib/neutron/metadata_proxy）相连，它再将请求发给本机上nova-api-metadata（DVR模式下每个计算节点都会有自己的nova-api-metadata）
已有数据分析
无奈，客户遇到问题了并在07-21 17.15重启了neutron-ovn-metadata-agent, 他抓的sosreport是在运行workaround之后抓的，参考价值有限啊．
他提到了这个namespace - ovnmeta-63e2c276-60dd-40e3-baa1-c16342eacce2, 所以搜索出如下信息，但是因为sosreport是在运行workaround之后抓的所以看不出什么问题.
$ grep -r 'tap63e2c276' sos_commands/networking/namespaces/ovnmeta-63e2c276-60dd-40e3-baa1-c16342eacce2/ip_netns_exec_ovnmeta-63e2c276-60dd-40e3-baa1-c16342eacce2_ip_-d_address_show
2: tap63e2c276-61@if20: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
inet 100.94.98.4/23 brd 100.94.99.255 scope global tap63e2c276-61
inet 169.254.169.254/32 brd 169.254.169.254 scope global tap63e2c276-61
但是根据这个IP (100.94.98.4)却搜不到东西（find var/log/neutron/* |xargs zgrep -i -E ‘100.94.98.4,’），但是却搜到了一个关于100.94.98.40的日志：
var/log/neutron/neutron-ovn-metadata-agent.log.1:2022-07-20 21:15:56.758 3872 ERROR neutron.agent.ovn.metadata.server [-] No port found in network 63e2c276-60dd-40e3-baa1-c16342eacce2 with IP address 100.94.98.40
这个日志来自代码./neutron/agent/ovn/metadata/server.py#_get_instance_and_project_id，在SB_DB里查询到的Port_Binding为0,
99 def _get_instance_and_project_id(self, req):
100 remote_address = req.headers.get('X-Forwarded-For')
101 network_id = req.headers.get('X-OVN-Network-ID')
102
103 ports = self.sb_idl.get_network_port_bindings_by_ip(network_id,
104 remote_address)
105 num_ports = len(ports)
106 if num_ports == 1:
107 external_ids = ports[0].external_ids
108 return (external_ids[ovn_const.OVN_DEVID_EXT_ID_KEY],
109 external_ids[ovn_const.OVN_PROJID_EXT_ID_KEY])
110 elif num_ports == 0:
111 LOG.error("No port found in network %s with IP address %s",
112 network_id, remote_address)
899 def get_network_port_bindings_by_ip(self, network, ip_address):
900 rows = self.db_list_rows('Port_Binding').execute(check_error=True)
901 # TODO(twilson) It would be useful to have a db_find that takes a
902 # comparison function
903
904 def check_net_and_ip(port):
905 # If the port is not bound to any chassis it is not relevant
906 if not port.chassis:
907 return False
908
909 # TODO(dalvarez): Remove the comparison to port.datapath.uuid in Y
910 # cycle when we are sure that all namespaces will be created with
911 # the Neutron network UUID and not anymore with the OVN datapath
912 # UUID.
913 is_in_network = lambda port: (
914 str(port.datapath.uuid) == network or
915 utils.get_network_name_from_datapath(port.datapath) == network)
916
917 return port.mac and is_in_network(port) and (
918 ip_address in port.mac[0].split(' '))
919
920 return [r for r in rows if check_net_and_ip(r)]
但是却搜不着和get_network_port_bindings_by_ip相关的东西（find var/log/neutron/* |xargs zgrep -i -E ‘get_network_port_bindings_by_ip’），所以应该不是连不着SB_DB的问题（若是连不上SB_DB，那运行get_network_port_bindings_by_ip时会出错，打出堆栈会有get_network_port_bindings_by_ip这个字眼吧？), 所以很有可能原因是真的Port_Binding就是0. 在我的测试环境上用’ovn-sbctl list Port_Binding’会看到下列数据(测试环境中的metadata port为192.168.21.2）：
_uuid : a011fdcd-15ba-48c3-aec0-2ef590aee864
chassis : []
datapath : 0f509be3-9b1f-4c66-9c59-ac4211cf5ef4
encap : []
external_ids : {"neutron:cidrs"="192.168.21.2/24", "neutron:device_id"=ovnmeta-8ea7d54e-5fe0-408d-9de8-5ccbed8ede84, "neutron:device_owner"="network:distributed", "neutron:network_name"=neutron-8ea7d54e-5fe0-408d-9de8-5ccbed8ede84, "neutron:port_name"="", "neutron:project_id"="728f2ae8aa8443b5a255574a5e236746", "neutron:revision_number"="2", "neutron:security_group_ids"=""}
gateway_chassis : []
ha_chassis_group : []
logical_port : "48244606-524d-4c24-bc54-0143869d4267"
mac : ["fa:16:3e:43:81:23 192.168.21.2"]
nat_addresses : []
options : {requested-chassis=""}
parent_port : []
tag : []
tunnel_key : 1
type : localport
up : false
virtual_parent : []
Port_Binding是谁创建的呢？
另外，nova-compute中大量这种日志, 似乎连不上neutron-api (9696)：
var/log/nova/nova-api-metadata.log:2022-07-21 13:41:24.086 1790270 ERROR nova.api.metadata.handler [req-42f38810-e2c3-4df0-8de6-754d1f6d5472 - - - - -] Failed to get metadata for instance id: 80f1bb26-f5db-4919-abb2-6b61d13f9267
和
var/log/nova/nova-api-metadata.log.20.gz:2022-07-01 20:21:46.371 3516 ERROR oslo.messaging._drivers.impl_rabbit [-] [e96b9581-fa77-4f0f-a580-05a13b18bfad] AMQP server on 192.168.0.124:5672 is unreachable: (0, 0): (320) CONNECTION_FORCED - broker forced connection closure with reason 'shutdown'. Trying again in 1 seconds.: amqp.exceptions.ConnectionForced: (0, 0): (320) CONNECTION_FORCED - broker forced connection closure with reason 'shutdown'
...
var/log/nova/nova-api-metadata.log.20.gz:2022-07-01 20:59:04.928 3514 ERROR nova.api.metadata.handler [req-c4d5a1b4-1c36-4864-b729-d68de13ef59d - - - - -] Failed to get metadata for instance id: cc1c7466-b5d4-47d0-8e23-e91c785fafb3: neutronclient.common.exceptions.NeutronClientException: <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
及
var/log/nova/nova-api-metadata.log.20.gz:2022-07-01 20:59:04.849 3514 ERROR nova.api.metadata.handler neutronclient.common.exceptions.NeutronClientException: <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
var/log/nova/nova-api-metadata.log.20.gz:2022-07-01 20:59:04.849 3514 ERROR nova.api.metadata.handler <html><head>
var/log/nova/nova-api-metadata.log.20.gz:2022-07-01 20:59:04.849 3514 ERROR nova.api.metadata.handler <title>502 Proxy Error</title>
var/log/nova/nova-api-metadata.log.20.gz:2022-07-01 20:59:04.849 3514 ERROR nova.api.metadata.handler </head><body>
var/log/nova/nova-api-metadata.log.20.gz:2022-07-01 20:59:04.849 3514 ERROR nova.api.metadata.handler <h1>Proxy Error</h1>
var/log/nova/nova-api-metadata.log.20.gz:2022-07-01 20:59:04.849 3514 ERROR nova.api.metadata.handler <p>The proxy server received an invalid^M
var/log/nova/nova-api-metadata.log.20.gz:2022-07-01 20:59:04.849 3514 ERROR nova.api.metadata.handler response from an upstream server.<br />^M
var/log/nova/nova-api-metadata.log.20.gz:2022-07-01 20:59:04.849 3514 ERROR nova.api.metadata.handler The proxy server could not handle the request<p>Reason: <strong>Error reading from remote server</strong></p></p>
var/log/nova/nova-api-metadata.log.20.gz:2022-07-01 20:59:04.849 3514 ERROR nova.api.metadata.handler <hr>
var/log/nova/nova-api-metadata.log.20.gz:2022-07-01 20:59:04.849 3514 ERROR nova.api.metadata.handler <address>Apache/2.4.41 (Ubuntu) Server at neutron.internal.api.xxx.infra.xxx.net Port 9696</address>
还有大量这种日志：
2022-07-20 23:59:18.828 1790159 INFO nova.compute.resource_tracker [req-25cb1333-d268-4870-877d-8465aea2b451 - - - - -] Instance 4d35b4ff-177c-4659-b6a4-d4d1d5ddecab has allocations against this compute host but is not found in the database.
也发现这种日志：
2022-07-11 16:37:25.769 2361 ERROR ovsdbapp.backend.ovs_idl.command Traceback (most recent call last):
2022-07-11 16:37:25.769 2361 ERROR ovsdbapp.backend.ovs_idl.command File "/usr/lib/python3/dist-packages/ovsdbapp/backend/ovs_idl/command.py", line 42, in execute
2022-07-11 16:37:25.769 2361 ERROR ovsdbapp.backend.ovs_idl.command t.add(self)
2022-07-11 16:37:25.769 2361 ERROR ovsdbapp.backend.ovs_idl.command File "/usr/lib/python3.8/contextlib.py", line 120, in __exit__
2022-07-11 16:37:25.769 2361 ERROR ovsdbapp.backend.ovs_idl.command next(self.gen)
2022-07-11 16:37:25.769 2361 ERROR ovsdbapp.backend.ovs_idl.command File "/usr/lib/python3/dist-packages/ovsdbapp/api.py", line 110, in transaction
2022-07-11 16:37:25.769 2361 ERROR ovsdbapp.backend.ovs_idl.command del self._nested_txns_map[cur_thread_id]
2022-07-11 16:37:25.769 2361 ERROR ovsdbapp.backend.ovs_idl.command File "/usr/lib/python3/dist-packages/ovsdbapp/api.py", line 61, in __exit__
2022-07-11 16:37:25.769 2361 ERROR ovsdbapp.backend.ovs_idl.command self.result = self.commit()
2022-07-11 16:37:25.769 2361 ERROR ovsdbapp.backend.ovs_idl.command File "/usr/lib/python3/dist-packages/ovsdbapp/backend/ovs_idl/transaction.py", line 57, in commit
2022-07-11 16:37:25.769 2361 ERROR ovsdbapp.backend.ovs_idl.command raise exceptions.TimeoutException(
2022-07-11 16:37:25.769 2361 ERROR ovsdbapp.backend.ovs_idl.command ovsdbapp.exceptions.TimeoutException: Commands [DbSetCommand(table=Chassis_Private, record=xxx.maas, col_values=(('external_ids', {'neutron:ovn-metadata-sb-cfg': '31205'}),))] exceeded timeout 180 seconds, cause: Result queue is empty
2022-07-11 16:37:25.769 2361 ERROR ovsdbapp.backend.ovs_idl.command
2022-07-11 16:37:25.780 2361 INFO ovsdbapp.backend.ovs_idl.vlog [-] ssl:100.94.0.158:6642: connected
2022-07-11 16:37:25.817 2361 INFO ovsdbapp.backend.ovs_idl.vlog [-] ssl:100.94.0.158:6642: clustered database server is not cluster leader; trying another server
2022-07-11 16:37:25.818 2361 INFO ovsdbapp.backend.ovs_idl.vlog [-] ssl:100.94.0.158:6642: connection closed by client
2022-07-11 16:37:33.831 2361 INFO ovsdbapp.backend.ovs_idl.vlog [-] ssl:100.94.0.204:6642: connected
2022-07-11 16:37:34.566 2361 INFO neutron.agent.ovn.metadata.agent [-] Connection to OVSDB established, doing a full sync
所以是metadata-agent连接SB_DB时超时导致查询到的port_binding为0了, 找到一个lp bug https://bugs.launchpad.net/neutron/+bug/1951841, 这个bug说system_id不为UUID时会报错，我们也看到了下列日志：
2022-07-11 18:57:45.926 798838 WARNING neutron.agent.ovn.metadata.agent [-] Can't read ovn-bridge external-id from OVSDB. Using br-int instead.
2022-07-11 18:57:45.926 798838 INFO neutron.agent.ovn.metadata.agent [-] Loaded chassis name xxx.maas (UUID: 4fe633c2-0c52-5c86-92b2-0ee1f5e71a90) and ovn bridge br-int.
2022-07-11 18:57:45.927 798838 INFO oslo_service.service [-] Starting 2 workers
308 def _get_ovn_bridge(self):
309 """Return the external_ids:ovn-bridge value of the Open_vSwitch table.
310
311 This is the OVS bridge used to plug the metadata ports to.
312 If the key doesn't exist, this method will return 'br-int' as default.
313 """
314 ext_ids = self.ovs_idl.db_get(
315 'Open_vSwitch', '.', 'external_ids').execute()
316 try:
317 return ext_ids['ovn-bridge']
318 except KeyError:
319 LOG.warning("Can't read ovn-bridge external-id from OVSDB. Using "
320 "br-int instead.")
321 return 'br-int'
但是取不到external_ids还是因为Port_Binding不存在啊？
排除lp bug 1951841
https://bugs.launchpad.net/neutron/+bug/1951841
ovn除了为计算节点添加Chassis记录(ovn-sbctl list Chassis), 还得为metadata-agent添加一个Chassis_Private记录(它根据Chassis system-id来生成Chassis_Private的agent-id．下面的代码中假设self.chassis_id是uuid，但实现charm部署的却不一定是uuid，这会导致neutron-ovn-metadata-agent运行可以但this produces that the neutron-ovn-metadata-agent daemon stays running but disconnected and new launched VMs won’t have access to the metadata service.
def register_metadata_agent(self):
# NOTE(lucasagomes): db_add() will not overwrite the UUID if
# it's already set.
table = ('Chassis_Private' if self.has_chassis_private else 'Chassis')
# Generate unique, but consistent metadata id for chassis name
agent_id = uuid.uuid5(self.chassis_id, 'metadata_agent')
ext_ids = {ovn_const.OVN_AGENT_METADATA_ID_KEY: str(agent_id)}
self.sb_idl.db_add(table, self.chassis, 'external_ids',
ext_ids).execute(check_error=True)
# ovn-sbctl list Chassis_Private
_uuid : 45524f21-0ca2-4736-a851-e5db69dad805
chassis : 4e2fabf4-3834-4137-8454-3525e541d652
external_ids : {"neutron:ovn-metadata-id"="26e2474c-75fc-5977-a311-828b9ad92180", "neutron:ovn-metadata-sb-cfg"="5"}
name : juju-3df241-ovn-8.cloud.sts
nb_cfg : 5
nb_cfg_timestamp : 1661337217145
做了下列实验未重现问题，可能是做一次不会稳定重现吗？
$ juju ssh nova-compute/0 sudo ip netns | grep ovnmeta
ovnmeta-0211506b-233e-4773-a034-3950dfefe23d
ovnmeta-8ea7d54e-5fe0-408d-9de8-5ccbed8ede84 (id: 0)
$ openstack server delete focal-103100
$ juju ssh nova-compute/0 sudo ip netns | grep ovnmeta
<empty>
$ juju status ovn-central | grep leader
ovn-central 21.09.0 active 3 ovn-central 21.09/stable 24 no Unit is ready (leader: ovnnb_db)
ovn-central/0 active idle 9 10.5.1.22 6641/tcp,6642/tcp Unit is ready (leader: ovnnb_db)
ovn-central/2* active idle 11 10.5.3.101 6641/tcp,6642/tcp Unit is ready (leader: ovnsb_db)
$ juju ssh $(juju status ovn-central | grep leader | tail -n 1 | awk '{print $1}' | tr -d '*') sudo reboot
#wait a few minutes
$ juju status ovn-central | grep leader
ovn-central 21.09.0 active 3 ovn-central 21.09/stable 24 no Unit is ready (leader: ovnnb_db)
ovn-central/0 active idle 9 10.5.1.22 6641/tcp,6642/tcp Unit is ready (leader: ovnnb_db)
ovn-central/1 active idle 10 10.5.0.186 6641/tcp,6642/tcp Unit is ready (leader: ovnsb_db northd: active)
$ ./tools/instance_launch.sh 1 focal
$ ./tools/float_all.sh
$ juju ssh nova-compute/0 sudo ip netns | grep ovnmeta
ovnmeta-8ea7d54e-5fe0-408d-9de8-5ccbed8ede84 (id: 0)
OVN中的Port_Binding表更新后会触发neutron中的 PortBindingUpdateVirtualPortsEvent 事件, 然后neutron的update_virtual_port_host再去neutron中创建PortBinding记录.
#https://bugs.launchpad.net/neutron/+bug/1951841/comments/28
neutron-ovn-metadata-agent如果每次启动用一个随机的agent-id来创建Private_Chassis的话，这个patch(https://github.com/openstack/neutron/commit/da3ce7319866e8dc874d405e91f9af160e2c3d31)改成不用随机的了，但是它使用了(chassis_id = uuid.UUID(self._get_own_chassis_name()) && agent_id = uuid.uuid5(chassis_id, ‘metadata_agent’))，这个会要求_get_own_chassis_name必须是一个uuid否则会抛异常．
为什么抛出了异常metada-agent就不再重新连接SB_DB去注册Private_Chassis了呢？那是因为ChassisCreateEventBase#run调用"self.agent.register_metadata_agent"第一次运行的时候因为first_time=true不会call self.agent.register_metadata_agent
def run(self, event, row, old):
if self.first_time:
self.first_time = False
else:
# NOTE(lucasagomes): Re-register the ovn metadata agent
# with the local chassis in case its entry was re-created
# (happens when restarting the ovn-controller)
self.agent.register_metadata_agent()
LOG.info("Connection to OVSDB established, doing a full sync")
self.agent.sync()
解决方法是支持让system-id为non-UUID - https://opendev.org/openstack/neutron/commit/6da4432fed255f3bcf3831f5d0520ab389ce36e5
但是这个代码已经在19.1.0里了，客户用的是19.3.0，显然不是这个bug
排除lp bug 1953510
#https://bugs.launchpad.net/neutron/+bug/1953510/comments/2
ovn-central端总会在做snapshot时做leader切换 - https://github.com/openvswitch/ovs/commit/3c2d6274bceecb65ec8f2f93f2aac26897a7ddfe
SB_DB端会看到日志：
$ find sosreport-juju-2752e1-*/var/log/ovn/* |xargs zgrep -i -E 'leadership'
sosreport-juju-2752e1-6-lxd-24-2022-08-18-entowko/var/log/ovn/ovsdb-server-sb.log:2022-08-18T12:30:35.322Z|80962|raft|INFO|Transferring leadership to write a snapshot.
sosreport-juju-2752e1-6-lxd-24-2022-08-18-entowko/var/log/ovn/ovsdb-server-sb.log:2022-08-18T12:30:35.610Z|80967|raft|INFO|received leadership transfer from 9b15 in term 295
sosreport-juju-2752e1-6-lxd-24-2022-08-18-entowko/var/log/ovn/ovsdb-server-sb.log:2022-08-18T17:52:53.024Z|82382|raft|INFO|Transferring leadership to write a snapshot.
sosreport-juju-2752e1-7-lxd-27-2022-08-18-hhxxqci/var/log/ovn/ovsdb-server-sb.log:2022-08-18T12:30:35.322Z|92695|raft|INFO|received leadership transfer from 0f3c in term 294
sosreport-juju-2752e1-7-lxd-27-2022-08-18-hhxxqci/var/log/ovn/ovsdb-server-sb.log:2022-08-18T12:30:35.330Z|92698|raft|INFO|Transferring leadership to write a snapshot.
sosreport-juju-2752e1-7-lxd-27-2022-08-18-hhxxqci/var/log/ovn/ovsdb-server-sb.log:2022-08-18T17:52:53.025Z|92893|raft|INFO|received leadership transfer from 0f3c in term 296
neutron端也会看到日志，这是在说刚好在写Chassis_Private时发生了leader切换吗？
2022-07-11 16:37:25.769 2361 ERROR ovsdbapp.backend.ovs_idl.command ovsdbapp.exceptions.TimeoutException: Commands [DbSetCommand(table=Chassis_Private, record=xxx.maas, col_values=(('external_ids', {'neutron:ovn-metadata-sb-cfg': '31205'}),))] exceeded timeout 180 seconds, cause: Result queue is empty
2022-07-11 16:37:25.769 2361 ERROR ovsdbapp.backend.ovs_idl.command
2022-07-11 16:37:25.780 2361 INFO ovsdbapp.backend.ovs_idl.vlog [-] ssl:100.94.0.158:6642: connected
2022-07-11 16:37:25.817 2361 INFO ovsdbapp.backend.ovs_idl.vlog [-] ssl:100.94.0.158:6642: clustered database server is not cluster leader; trying another server
进一步的流程分析
1, ovn-controller中的chassis_run上报chassis信息，并在SBDB中创建Chassis记录.
2, ovn-northd中的sbrec_port_binding_insert负责将NB_DB中的port(包含lsp和lrp)插入SB_DB的Port_Binding table， 见： ovn-northd 源码分析 - http://events.jianshu.io/p/e2139ecd0463
ovn-northd -vconsole:emer -vsyslog:err -vfile:info --ovnnb-db=ssl:100.94.0.158:6641,ssl:100.94.0.99:6641,ssl:100.94.0.204:6641 --ovnsb-db=ssl:100.94.0.158:16642,ssl:100.94.0.99:16642,ssl:100.94.0.204:16642 -c /etc/ovn/cert_host -C /etc/ovn/ovn-central.crt -p /etc/ovn/key_host --no-chdir --log-file=/var/log/ovn/ovn-northd.log --pidfile=/var/run/ovn/ovn-northd.pid --detach
2022-08-18T09:15:46.193Z|28332|ovsdb_cs|INFO|ssl:100.94.0.204:16642: clustered database server is not cluster leader; trying another server
2022-08-18T09:15:46.193Z|28333|reconnect|INFO|ssl:100.94.0.204:16642: connection attempt timed out
2022-08-18T09:15:46.194Z|28334|reconnect|INFO|ssl:100.94.0.99:16642: connecting...
2022-08-18T09:15:46.199Z|28335|reconnect|INFO|ssl:100.94.0.99:16642: connected
2022-08-18T09:15:46.201Z|28336|ovn_northd|INFO|ovn-northd lock acquired. This ovn-northd instance is now active.
2022-08-18T09:15:46.202Z|28337|northd|WARN|Dropped 3 log messages in last 86113 seconds (most recently, 86113 seconds ago) due to excessive rate
2022-08-18T09:15:46.202Z|28338|northd|WARN|Chassis does not exist for Chassis_Private record, name: juju-2752e1-5-lxd-24.maas
2022-08-18T09:15:46.202Z|28339|ovsdb_cs|INFO|ssl:100.94.0.99:16642: clustered database server is not cluster leader; trying another server
2022-08-18T09:15:46.203Z|28340|reconnect|INFO|ssl:100.94.0.99:16642: connection attempt timed out
2022-08-18T09:15:46.203Z|28341|ovn_northd|INFO|ovn-northd lock lost. This ovn-northd instance is now on standby.
2022-08-18T09:15:46.203Z|28342|reconnect|INFO|ssl:100.94.0.158:16642: connecting...
2022-08-18T09:15:46.207Z|28343|reconnect|INFO|ssl:100.94.0.158:16642: connected
2022-08-18T09:15:46.209Z|28344|ovn_northd|INFO|ovn-northd lock acquired. This ovn-northd instance is now active.
2022-08-18T09:15:46.210Z|28345|ovsdb_cs|INFO|ssl:100.94.0.158:16642: clustered database server is not cluster leader; trying another server
2022-08-18T09:15:46.210Z|28346|reconnect|INFO|ssl:100.94.0.158:16642: connection attempt timed out
2022-08-18T09:15:46.210Z|28347|ovn_northd|INFO|ovn-northd lock lost. This ovn-northd instance is now on standby.
2022-08-18T09:15:46.210Z|28348|reconnect|INFO|ssl:100.94.0.204:16642: connecting...
2022-08-18T09:15:46.215Z|28349|reconnect|INFO|ssl:100.94.0.204:16642: connected
3, ovn-northd一直有上面的日志显示连不上SB_DB，从而导致无法插入Port_Binding, 那么neutron也不会收到PortBindingUpdateVirtualPortsEvent事件，那么neutron也不会通过update_virtual_port_host在neutron中创建PortBinding记录
4, 这样neutron-medadata-agent的_get_instance_and_project_id查询Port_Binding为0, 也就有了：
var/log/neutron/neutron-ovn-metadata-agent.log.1:2022-07-20 21:15:56.758 3872 ERROR neutron.agent.ovn.metadata.server [-] No port found in network 63e2c276-60dd-40e3-baa1-c16342eacce2 with IP address 100.94.98.40
5, SB_DB leader老在切换， 切换过程中刚好创建虚机的话可能报下列错．
2022-07-11 16:37:25.769 2361 ERROR ovsdbapp.backend.ovs_idl.command ovsdbapp.exceptions.TimeoutException: Commands [DbSetCommand(table=Chassis_Private, record=xxx.maas, col_values=(('external_ids', {'neutron:ovn-metadata-sb-cfg': '31205'}),))] exceeded timeout 180 seconds, cause: Result queue is empty
6, 这种日志还是因为Port_Binding不存在，才取不到Port_Bidning中的external_ids - Can't read ovn-bridge external-id from OVSD
7, Port_Binding不存在，又回到了上面的第2步(Port_Binding是由ovn_northd创建的，它连不上SB_DB), 所以是SB_DB的问题
8, 为啥SB_DB有问题？
$ grep -r 'leader' sosreport-juju-2752e1-*/var/log/ovn/ovsdb-server-sb.log
sosreport-juju-2752e1-5-lxd-23--2022-08-18-bnsdhsj/var/log/ovn/ovsdb-server-sb.log:2022-08-18T09:15:49.863Z|31963|raft|INFO|server 0f3c is leader for term 294
sosreport-juju-2752e1-5-lxd-23--2022-08-18-bnsdhsj/var/log/ovn/ovsdb-server-sb.log:2022-08-18T12:30:35.330Z|32086|raft|INFO|server 9b15 is leader for term 295
sosreport-juju-2752e1-5-lxd-23--2022-08-18-bnsdhsj/var/log/ovn/ovsdb-server-sb.log:2022-08-18T12:30:35.613Z|32088|raft|INFO|server 0f3c is leader for term 296
sosreport-juju-2752e1-5-lxd-23--2022-08-18-bnsdhsj/var/log/ovn/ovsdb-server-sb.log:2022-08-18T17:52:53.379Z|32327|raft|INFO|server 9b15 is leader for term 297
sosreport-juju-2752e1-6-lxd-24--2022-08-18-entowko/var/log/ovn/ovsdb-server-sb.log:2022-08-18T09:15:49.862Z|80388|raft|INFO|term 294: elected leader by 2+ of 3 servers
sosreport-juju-2752e1-6-lxd-24--2022-08-18-entowko/var/log/ovn/ovsdb-server-sb.log:2022-08-18T12:30:35.322Z|80962|raft|INFO|Transferring leadership to write a snapshot.
sosreport-juju-2752e1-6-lxd-24--2022-08-18-entowko/var/log/ovn/ovsdb-server-sb.log:2022-08-18T12:30:35.324Z|80963|raft|INFO|rejected append_reply (not leader)
sosreport-juju-2752e1-6-lxd-24--2022-08-18-entowko/var/log/ovn/ovsdb-server-sb.log:2022-08-18T12:30:35.609Z|80964|raft|INFO|rejected append_reply (not leader)
sosreport-juju-2752e1-6-lxd-24--2022-08-18-entowko/var/log/ovn/ovsdb-server-sb.log:2022-08-18T12:30:35.609Z|80965|raft|INFO|rejected append_reply (not leader)
sosreport-juju-2752e1-6-lxd-24--2022-08-18-entowko/var/log/ovn/ovsdb-server-sb.log:2022-08-18T12:30:35.610Z|80966|raft|INFO|server 9b15 is leader for term 295
sosreport-juju-2752e1-6-lxd-24--2022-08-18-entowko/var/log/ovn/ovsdb-server-sb.log:2022-08-18T12:30:35.610Z|80967|raft|INFO|received leadership transfer from 9b15 in term 295
sosreport-juju-2752e1-6-lxd-24--2022-08-18-entowko/var/log/ovn/ovsdb-server-sb.log:2022-08-18T12:30:35.613Z|80969|raft|INFO|term 296: elected leader by 2+ of 3 servers
sosreport-juju-2752e1-6-lxd-24--2022-08-18-entowko/var/log/ovn/ovsdb-server-sb.log:2022-08-18T17:52:53.024Z|82382|raft|INFO|Transferring leadership to write a snapshot.
sosreport-juju-2752e1-6-lxd-24--2022-08-18-entowko/var/log/ovn/ovsdb-server-sb.log:2022-08-18T17:52:53.367Z|82383|raft|INFO|rejected append_reply (not leader)
sosreport-juju-2752e1-6-lxd-24--2022-08-18-entowko/var/log/ovn/ovsdb-server-sb.log:2022-08-18T17:52:53.378Z|82384|raft|INFO|server 9b15 is leader for term 297
sosreport-juju-2752e1-7-lxd-27--2022-08-18-hhxxqci/var/log/ovn/ovsdb-server-sb.log:2022-08-18T09:15:51.200Z|92562|raft|INFO|server 0f3c is leader for term 294
sosreport-juju-2752e1-7-lxd-27--2022-08-18-hhxxqci/var/log/ovn/ovsdb-server-sb.log:2022-08-18T12:30:35.322Z|92695|raft|INFO|received leadership transfer from 0f3c in term 294
sosreport-juju-2752e1-7-lxd-27--2022-08-18-hhxxqci/var/log/ovn/ovsdb-server-sb.log:2022-08-18T12:30:35.330Z|92697|raft|INFO|term 295: elected leader by 2+ of 3 servers
sosreport-juju-2752e1-7-lxd-27--2022-08-18-hhxxqci/var/log/ovn/ovsdb-server-sb.log:2022-08-18T12:30:35.330Z|92698|raft|INFO|Transferring leadership to write a snapshot.
sosreport-juju-2752e1-7-lxd-27--2022-08-18-hhxxqci/var/log/ovn/ovsdb-server-sb.log:2022-08-18T12:30:35.334Z|92699|raft|INFO|rejected append_reply (not leader)
sosreport-juju-2752e1-7-lxd-27--2022-08-18-hhxxqci/var/log/ovn/ovsdb-server-sb.log:2022-08-18T12:30:35.728Z|92700|raft|INFO|server 0f3c is leader for term 296
sosreport-juju-2752e1-7-lxd-27--2022-08-18-hhxxqci/var/log/ovn/ovsdb-server-sb.log:2022-08-18T17:52:53.025Z|92893|raft|INFO|received leadership transfer from 0f3c in term 296
sosreport-juju-2752e1-7-lxd-27--2022-08-18-hhxxqci/var/log/ovn/ovsdb-server-sb.log:2022-08-18T17:52:53.378Z|92895|raft|INFO|term 297: elected leader by 2+ of 3 servers
然后就搜到了这个:
$ find sosreport-juju-2752e1-*/var/log/ovn/* |xargs zgrep -i -E 'inactivity'
sosreport-juju-2752e1-7-lxd-27-2022-08-18-hhxxqci/var/log/ovn/ovsdb-server-nb.log:2022-08-18T09:15:49.882Z|657323|reconnect|ERR|ssl:100.94.0.99:40308: no response to inactivity probe after 5 seconds, disconnecting
sosreport-juju-2752e1-7-lxd-27-2022-08-18-hhxxqci/var/log/ovn/ovsdb-server-nb.log:2022-08-18T09:15:49.883Z|657324|reconnect|ERR|ssl:100.94.0.158:51592: no response to inactivity probe after 5 seconds, disconnecting
sosreport-juju-2752e1-7-lxd-27-2022-08-18-hhxxqci/var/log/ovn/ovsdb-server-sb.log:2022-08-18T09:15:47.313Z|92550|reconnect|ERR|ssl:100.94.0.158:6644: no response to inactivity probe after 5 seconds, disconnecting
sosreport-juju-2752e1-7-lxd-27-2022-08-18-hhxxqci/var/log/ovn/ovsdb-server-sb.log:2022-08-18T09:15:49.815Z|92555|reconnect|ERR|ssl:100.94.0.99:45744: no response to inactivity probe after 5 seconds, disconnecting
sosreport-juju-2752e1-7-lxd-27-2022-08-18-hhxxqci/var/log/ovn/ovsdb-server-sb.log:2022-08-18T09:15:49.816Z|92556|reconnect|ERR|ssl:100.94.0.158:44928: no response to inactivity probe after 5 seconds, disconnecting
可搜索’20220427 - ovn performance issue’ - https://blog.csdn.net/quqi99/article/details/103194137 , 得试试：
# on compute chassis
ovs-vsctl set open . external_ids:ovn-openflow-probe-interval=0
ovs-vsctl set open . external_ids:ovn-monitor-all=true
ovs-vsctl set open . external_ids:ovn-remote-probe-interval=100000
$ sudo ovs-vsctl get open . external_ids
{hostname=juju-3df241-ovn-8.cloud.sts, ovn-bridge-mappings="physnet1:br-data", ovn-encap-ip="10.5.0.110", ovn-encap-type=geneve, ovn-match-northd-version="true", ovn-remote="ssl:10.5.1.22:6642,ssl:10.5.0.186:6642,ssl:10.5.3.101:6642", rundir="/var/run/openvswitch", system-id=juju-3df241-ovn-8.cloud.sts}
#on SB_DB and NB_DB
ovn-nbctl set connection . inactivity_probe='180000'
ovn-sbctl set connection . inactivity_probe='180000'
ovn-nbctl get connection . inactivity_probe
#juju
juju config ovn-central ovsdb-server-inactivity-probe
确定SB_DB的问题
可以在每个ovn-central unit上运行"ovn-appctl -t ovn-northd status", 它用来告诉unit是active还是standby，但如果stuck就说明ovn-northd状态不对，可能需要重启ovn-northd，这个可排除是否所有ovn-central unit都有问题．
还有如下命令：
#https://github.com/sosreport/sos/commit/499b1ebd1341b524eca294762332939fe0408416
#cat sos_commands/ovn_central/ovs-appctl_-t_.var.run.ovn.ovnnb_db.ctl_cluster.status_OVN_Northbound
$ ls /var/run/ovn/*.ctl
$ sudo ovs-appctl -t /var/run/ovn/ovnnb_db.ctl cluster/status OVN_Northbound
2394
Name: OVN_Northbound
Cluster ID: 74bc (74bcea93-e506-4c88-97bf-e0094b9ca634)
Server ID: 2394 (23940573-b5be-465a-9e0f-b3ab9941335d)
Address: ssl:10.5.3.101:6643
Status: cluster member
Role: follower
Term: 7
Leader: ad8a
Vote: ad8a
Last Election started 5567642 ms ago, reason: timeout
Election timer: 4000
Log: [93, 100]
Entries not yet committed: 0
Entries not yet applied: 0
Connections: ->f38b ->ad8a <-f38b <-ad8a
Disconnections: 0
Servers:
f38b (f38b at ssl:10.5.1.22:6643) last msg 5564502 ms ago
ad8a (ad8a at ssl:10.5.0.186:6643) last msg 197 ms ago
2394 (2394 at ssl:10.5.3.101:6643) (self)
$ sudo ovs-appctl -t /var/run/ovn/ovnsb_db.ctl cluster/status OVN_Southbound
3dd6
Name: OVN_Southbound
Cluster ID: 0993 (09934a9f-1948-48ec-9cba-da7c6efba970)
Server ID: 3dd6 (3dd60330-5607-4817-bc53-1e08ad972c02)
Address: ssl:10.5.3.101:6644
Status: cluster member
Role: follower
Term: 10
Leader: 9c8f
Vote: self
Last Election started 5620622 ms ago, reason: timeout
Election timer: 4000
Log: [114, 125]
Entries not yet committed: 0
Entries not yet applied: 0
Connections: ->8ff3 ->9c8f <-9c8f <-8ff3
Disconnections: 0
Servers:
3dd6 (3dd6 at ssl:10.5.3.101:6644) (self)
8ff3 (8ff3 at ssl:10.5.0.186:6644) last msg 5619344 ms ago
9c8f (9c8f at ssl:10.5.1.22:6644) last msg 222 ms ago
Event Timeline
1, on 2022-07-11, SB_DB should be bad so neutron-ovn-metadata-agent reported a error 'exceeded timeout 180 seconds, cause: Result queue is empty'
2022-07-11 16:37:25.769 2361 ERROR ovsdbapp.backend.ovs_idl.command ovsdbapp.exceptions.TimeoutException: Commands [DbSetCommand(table=Chassis_Private, record=xxx.maas, col_values=(('external_ids', {'neutron:ovn-metadata-sb-cfg': '31205'}),))] exceeded timeout 180 seconds, cause: Result queue is empty
2022-07-11 16:37:25.769 2361 ERROR ovsdbapp.backend.ovs_idl.command
2022-07-11 16:37:25.780 2361 INFO ovsdbapp.backend.ovs_idl.vlog [-] ssl:100.94.0.158:6642: connected
2022-07-11 16:37:25.817 2361 INFO ovsdbapp.backend.ovs_idl.vlog [-] ssl:100.94.0.158:6642: clustered database server is not cluster leader; trying another server
2022-07-11 16:37:25.818 2361 INFO ovsdbapp.backend.ovs_idl.vlog [-] ssl:100.94.0.158:6642: connection closed by client
2022-07-11 16:37:33.831 2361 INFO ovsdbapp.backend.ovs_idl.vlog [-] ssl:100.94.0.204:6642: connected
2022-07-11 16:37:34.566 2361 INFO neutron.agent.ovn.metadata.agent [-] Connection to OVSDB established, doing a full sync
This error should have nothing to do with this issue because it happened on 2022-07-11, not on 2022-08-18
2, on 2022-08-18, SB_DB was good, because I just found the error 'exceeded timeout 180 seconds, cause: Result queue is empty' in sosreport-xxx-2022-07-21-baldxuf, not in sosreport-xxx-2022-08-18-bgnovqu
3, at 2022-08-18T09:15:47, one inactivity probe error happened
var/log/ovn/ovsdb-server-sb.log:2022-08-18T09:15:47.313Z|92550|reconnect|ERR|ssl:100.94.0.158:6644: no response to inactivity probe after 5 seconds, disconnecting
sosreport shows 100.94.0.204 is the leader at that time, so this inactivity probe means the leader 100.94.0.204 didn't receive the reply from 100.94.0.158:6644 within 5 seconds then it disconnected the TCP connection between 100.94.0.204 and 100.94.0.158 to avoid waste of resources. So it should not be the key of the problem.
5-lxd-23: f801 100.94.0.99:6644 follower term=297
6-lxd-24: 0f3c 100.94.0.158:6644 follower term=297
7-lxd-27: 9b15 100.94.0.204:6644 leader term=297 leader
4, at 2022-08-18 09:15:50, neutron-ovn-metadata-agent started to call self.agent.register_metadata_agent() to create Private_Chassis in SB_DB
$ find sosreport-srv1ibm00*/var/log/neutron/* |xargs zgrep -i -E 'Connection to OVSDB established, doing a full'
xxx/var/log/neutron/neutron-ovn-metadata-agent.log:2022-08-18 09:15:50.726 75556 INFO neutron.agent.ovn.metadata.agent [-] Connection to OVSDB established, doing a full sync
def run(self, event, row, old):
if self.first_time:
self.first_time = False
else:
# NOTE(lucasagomes): Re-register the ovn metadata agent
# with the local chassis in case its entry was re-created
# (happens when restarting the ovn-controller)
self.agent.register_metadata_agent()
LOG.info("Connection to OVSDB established, doing a full sync")
self.agent.sync()
5, at 2022-08-18T12:30:35, reelection took place due to snapshot factor
$ find sosreport-juju-2752e1-*/var/log/ovn/* |xargs zgrep -i -E 'received leadership transfer from'
sosreport-juju-2752e1-6-lxd-24-xxx/var/log/ovn/ovsdb-server-sb.log:2022-08-18T12:30:35.610Z|80967|raft|INFO|received leadership transfer from 9b15 in term 295
sosreport-juju-2752e1-7-lxd-27-xxx/var/log/ovn/ovsdb-server-sb.log:2022-08-18T12:30:35.322Z|92695|raft|INFO|received leadership transfer from 0f3c in term 294
sosreport-juju-2752e1-7-lxd-27-xxx/var/log/ovn/ovsdb-server-sb.log:2022-08-18T17:52:53.025Z|92893|raft|INFO|received leadership transfer from 0f3c in term 296
# reelection was caused by snapshot factor according to timestamp
$ find sosreport-juju-2752e1-*/var/log/ovn/* |xargs zgrep -i -E 'Transferring leadership'
sosreport-juju-2752e1-6-lxd-24-xxx/var/log/ovn/ovsdb-server-sb.log:2022-08-18T12:30:35.322Z|80962|raft|INFO|Transferring leadership to write a snapshot.
sosreport-juju-2752e1-6-lxd-24-xxx/var/log/ovn/ovsdb-server-sb.log:2022-08-18T17:52:53.024Z|82382|raft|INFO|Transferring leadership to write a snapshot.
sosreport-juju-2752e1-7-lxd-27-xxx/var/log/ovn/ovsdb-server-sb.log:2022-08-18T12:30:35.330Z|92698|raft|INFO|Transferring leadership to write a snapshot.
6, at 2022-08-18 12:30:36, neutron-ovn-metadata-agent can't query port from SB_DB
$ find sosreport-srv1ibm00*/var/log/neutron/* |xargs zgrep -i -E 'OVSDB Error'
sosreport-srv1ibm002d-xxx/var/log/neutron/neutron-ovn-metadata-agent.log:2022-08-18 12:30:36.103 75556 ERROR ovsdbapp.backend.ovs_idl.transaction [-] OVSDB Error: no error details available
sosreport-srv1ibm006d-xxx/var/log/neutron/neutron-ovn-metadata-agent.log:2022-08-18 12:30:36.104 2171 ERROR ovsdbapp.backend.ovs_idl.transaction [-] OVSDB Error: no error details available
7, at 2022-08-18 12:57:53, metadata port can't be created
2022-08-18 12:57:53.800 3730 ERROR neutron.agent.ovn.metadata.server [-] No port found in network 63e2c276-60dd-40e3-baa1-c16342eacce2 with IP address 100.94.98.135
8, at 2022-08-18 18:30:01, run the workaround to restart neutron-ovn-metadata-agent.service
所以这个问题是SB_DB在snapshot前做leadership的迁移的时候neutron又在创建metadata port，我们当然可以让snapshot的频率变低（https://bugs.launchpad.net/ubuntu/+source/openvswitch/+bug/1990978，这个特性在ovs=2.17.3里可用，客户用的是focal-xena: 2.16.0-0ubuntu2.1~cloud0）．但是即使SB_DB做leadership时也不能让创建metadata port就失败啊, 这个lp bug ( https://bugs.launchpad.net/neutron/+bug/1961013 )让neutron可以连接一个read-only的non-leader节点来减少失败率.
但neutron是在创建metadata port是在写啊？
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