7.7 KiB
Live migrate Neutron routers (OVS/ML2)
Introduction
Neutron routers are hosted by L3 Agents running on neutron-gateway units.
When the unit(s) need to be brought down for maintenance, routers need
to be migrated to another unit that will host them during the
downtime.
Note
This tutorial deals with migration of a router strictly in the
OVS/ML2 environment, deployments using OVN have different topology in
which routers are not hosted by individual L3 Agents.
Warning
Migration of a router will cause brief disruption of a traffic between networks connected to the router.
Example topology
To demonstrate steps needed for the migration, we will use openstack deployment with three neutron-gateway units:
Unit Workload Agent Machine Public address Ports Message
neutron-gateway/0* active idle 0 10.5.1.149 Unit is ready
ntp/0* active idle 10.5.1.149 123/udp chrony: Ready
neutron-gateway/1 active idle 13 10.5.2.17 Unit is ready
ntp/4 active idle 10.5.2.17 123/udp chrony: Ready
neutron-gateway/2 active idle 14 10.5.0.159 Unit is ready
ntp/5 active idle 10.5.0.159 123/udp chrony: Ready
Machine State DNS Inst id Series AZ Message
0 started 10.5.1.149 1bf707d8-3e27-473f-b597-5cfc43c50b85 bionic nova ACTIVE
13 started 10.5.2.17 960d3868-a5a3-443c-99a8-acbcec7a4272 bionic nova ACTIVE
14 started 10.5.0.159 c8c75144-7a5b-49c0-bfb5-4910c6501f21 bionic nova ACTIVEEach of these units hosts single L3 Agent:
openstack network agent list --agent-type l3
+--------------------------------------+------------+-------------------+-------------------+-------+-------+------------------+
| ID | Agent Type | Host | Availability Zone | Alive | State | Binary |
+--------------------------------------+------------+-------------------+-------------------+-------+-------+------------------+
| 6226d159-ed57-4dfb-a311-ae36d2b4462b | L3 agent | juju-56ea63-os-0 | nova | :-) | UP | neutron-l3-agent |
| 6ae7ed32-7aa4-460c-8eb7-d13f4e651fcc | L3 agent | juju-56ea63-os-13 | nova | :-) | UP | neutron-l3-agent |
| b066c34d-aa91-46fe-9b20-f19f4a297932 | L3 agent | juju-56ea63-os-14 | nova | :-) | UP | neutron-l3-agent |
+--------------------------------------+------------+-------------------+-------------------+-------+-------+------------------+And we will be bringing down unit neutron-gateway/2 for
maintenance.
Procedure
Find out which routers run on our targeted unit
Referencing our example topology above, we are about to bring down
unit neutron-gateway/2. We need to find out which routers
are hosted on it. We can see that this unit is running on machine
14, listing all the L3 Agents we get:
openstack network agent list --agent-type l3
+--------------------------------------+------------+-------------------+-------------------+-------+-------+------------------+
| ID | Agent Type | Host | Availability Zone | Alive | State | Binary |
+--------------------------------------+------------+-------------------+-------------------+-------+-------+------------------+
| 6226d159-ed57-4dfb-a311-ae36d2b4462b | L3 agent | juju-56ea63-os-0 | nova | :-) | UP | neutron-l3-agent |
| 6ae7ed32-7aa4-460c-8eb7-d13f4e651fcc | L3 agent | juju-56ea63-os-13 | nova | :-) | UP | neutron-l3-agent |
| b066c34d-aa91-46fe-9b20-f19f4a297932 | L3 agent | juju-56ea63-os-14 | nova | :-) | UP | neutron-l3-agent |
+--------------------------------------+------------+-------------------+-------------------+-------+-------+------------------+Machine 14 corresponds to Host
juju-56ea63-os-14, so we need to find out which routers are
hosted on the L3 agent with ID
b066c34d-aa91-46fe-9b20-f19f4a297932.
openstack router list --agent b066c34d-aa91-46fe-9b20-f19f4a297932
+--------------------------------------+-----------------+--------+-------+-------------+-------+----------------------------------+
| ID | Name | Status | State | Distributed | HA | Project |
+--------------------------------------+-----------------+--------+-------+-------------+-------+----------------------------------+
| 35dcce1b-f69f-4af3-b46f-54249812ec9f | provider-router | ACTIVE | UP | False | False | b800e60c5e3841fbbb8b1dbc02ce13e3 |
+--------------------------------------+-----------------+--------+-------+-------------+-------+----------------------------------+This means that we need to move router with name
provider-router to a different agent.
Move router to a different agent
This is the part that will cause brief disruption of a traffic as routers can not be moved seamlessly. Moving consists of manually removing router from one agent and adding it to another. First we double-check that the router is hosted on the agent that is about to go down:
openstack network agent list --router provider-router
+--------------------------------------+------------+-------------------+-------------------+-------+-------+------------------+
| ID | Agent Type | Host | Availability Zone | Alive | State | Binary |
+--------------------------------------+------------+-------------------+-------------------+-------+-------+------------------+
| b066c34d-aa91-46fe-9b20-f19f4a297932 | L3 agent | juju-56ea63-os-14 | nova | :-) | UP | neutron-l3-agent |
+--------------------------------------+------------+-------------------+-------------------+-------+-------+------------------+Now we remove the router from this agent and assign it to an agent
running on the unit neutron-gateway/0 with agent ID
6226d159-ed57-4dfb-a311-ae36d2b4462b. Note that this will
increase the load on the neutron-gateway/0 unit. Make sure
that the machine hosting this unit has enough resources to accommodate
the additional router.
openstack network agent remove router b066c34d-aa91-46fe-9b20-f19f4a297932 provider-router --l3
openstack network agent add router 6226d159-ed57-4dfb-a311-ae36d2b4462b provider-router --l3Result of this move can be checked by:
openstack network agent list --router provider-router
+--------------------------------------+------------+------------------+-------------------+-------+-------+------------------+
| ID | Agent Type | Host | Availability Zone | Alive | State | Binary |
+--------------------------------------+------------+------------------+-------------------+-------+-------+------------------+
| 6226d159-ed57-4dfb-a311-ae36d2b4462b | L3 agent | juju-56ea63-os-0 | nova | :-) | UP | neutron-l3-agent |
+--------------------------------------+------------+------------------+-------------------+-------+-------+------------------+