efca596141
That script was lacking some comments and explainations about how it works, what it does and its limitations Change-Id: I7c5badf03f7903f42e33d5dfa750c76ddca882c4
Neutron folder
this folder contains scripts that are related to Neutron
L3 Agent Evacuate
Migrate away the OpenStack routers from a L3 Agent
./l3-agent-evacuate.py --help
usage: l3-agent-evacuate.py [-h] [-f FROM_L3AGENT] [-t TO_L3AGENT] [-r ROUTER]
[-l LIMIT] [-v]
Evacuate a neutron l3-agent
optional arguments:
-h, --help show this help message and exit
-f FROM_L3AGENT, --from-l3agent FROM_L3AGENT
l3agent uuid
-t TO_L3AGENT, --to-l3agent TO_L3AGENT
l3agent uuid
-r ROUTER, --router ROUTER
specific router
-l LIMIT, --limit LIMIT
max number of routers to migrate
-v, --verbose verbose
First of all we should have clear in mind that when we create a router in Openstack, that router is just a network namespace on one of the network nodes, with name qrouter-. For each namespace there is a qr (downstream) and a qg (upstream) interface. In some situations an operation might want to migrate away all the routers from a network node, to be able for example to reboot the node without impacting the user traffic. The neutron component responsible for creating the namespaces and cabling them with openvswitch is the l3 agent. You can check the uuid of the l3 agents currently running with:
openstack network agent list
When you are running multiple l3 agents, if you create a new router Openstack will schedule the namespace to be created on one of the available network nodes. Given a specific router, with this command you can find out on which network node the namespace has been created:
neutron l3-agent-list-hosting-router <router_uuid>
To list instead all the routers scheduled on a specific network node neutron router-list-on-l3-agent <l3agent-uuid> Using the neutron commands
l3-agent-router-add and l3-agent-router-remove is then possible to move a
router from a l3 agent to another one.
The tool l3-agent-evacuate.py will create a list of all the routers present
on the from-agent and will move 1 router every 10 seconds to the to-agent.
It is better to add a 10 seconds delay because Openvswitch has to make a lot of
operations when the namespace is created, and moving many routers at once will
cause openvswitch to blow up with unpredictable behavior.
The script has also a --router option if you want to migrate a specific
router, or a --limit option if you want to migrate just a few routers.
While migrating the routers, you can check (especially on the target l3-agent)
the openvswitch operations going on in /var/log/syslog.