Scalable and highly available DHCP agentsThis section describes how to use the agent management
(alias agent) and scheduler (alias agent_scheduler) extensions
for DHCP agents scalability and HA.Use the neutron ext-list client
command to check if these extensions are enabled:
$neutron ext-list -c name -c alias+-----------------+--------------------------+
| alias | name |
+-----------------+--------------------------+
| agent_scheduler | Agent Schedulers |
| binding | Port Binding |
| quotas | Quota management support |
| agent | agent |
| provider | Provider Network |
| router | Neutron L3 Router |
| lbaas | LoadBalancing service |
| extraroute | Neutron Extra Route |
+-----------------+--------------------------+
There will be three hosts in the setup.
Hosts for demo
Host
Description
OpenStack Controller host - controlnode
Runs the Neutron, Keystone, and Nova
services that are required to deploy VMs.
The node must have at least one network
interface that is connected to the
Management Network.Note that nova-network should
not be running because it is replaced
by Neutron.
HostA
Runs Nova compute, the Neutron L2 agent and
DHCP agent
HostB
Same as HostA
Configurationcontrolnode—Neutron ServerNeutron configuration file
/etc/neutron/neutron.conf:[DEFAULT]
core_plugin = neutron.plugins.linuxbridge.lb_neutron_plugin.LinuxBridgePluginV2
rabbit_host = controlnode
allow_overlapping_ips = True
host = controlnode
agent_down_time = 5Update the plug-in configuration file
/etc/neutron/plugins/linuxbridge/linuxbridge_conf.ini:[vlans]
tenant_network_type = vlan
network_vlan_ranges = physnet1:1000:2999
[database]
connection = mysql://root:root@127.0.0.1:3306/neutron_linux_bridge
retry_interval = 2
[linux_bridge]
physical_interface_mappings = physnet1:eth0HostA and HostB—L2 AgentNeutron configuration file
/etc/neutron/neutron.conf:[DEFAULT]
rabbit_host = controlnode
rabbit_password = openstack
# host = HostB on hostb
host = HostAUpdate the plug-in configuration file
/etc/neutron/plugins/linuxbridge/linuxbridge_conf.ini:[vlans]
tenant_network_type = vlan
network_vlan_ranges = physnet1:1000:2999
[database]
connection = mysql://root:root@127.0.0.1:3306/neutron_linux_bridge
retry_interval = 2
[linux_bridge]
physical_interface_mappings = physnet1:eth0Update the nova configuration file
/etc/nova/nova.conf:[DEFAULT]
network_api_class=nova.network.neutronv2.api.API
neutron_admin_username=neutron
neutron_admin_password=servicepassword
neutron_admin_auth_url=http://controlnode:35357/v2.0/
neutron_auth_strategy=keystone
neutron_admin_tenant_name=servicetenant
neutron_url=http://100.1.1.10:9696/
firewall_driver=nova.virt.firewall.NoopFirewallDriverHostA and HostB—DHCP AgentUpdate the DHCP configuration file
/etc/neutron/dhcp_agent.ini:[DEFAULT]
interface_driver = neutron.agent.linux.interface.BridgeInterfaceDriverCommands in agent management and scheduler
extensionsThe following commands require the tenant running the
command to have an admin role.Ensure that the following environment variables are
set. These are used by the various clients to access
Keystone.export OS_USERNAME=admin
export OS_PASSWORD=adminpassword
export OS_TENANT_NAME=admin
export OS_AUTH_URL=http://controlnode:5000/v2.0/SettingsTo experiment, you need VMs and a neutron
network:$nova list+--------------------------------------+-----------+--------+---------------+
| ID | Name | Status | Networks |
+--------------------------------------+-----------+--------+---------------+
| c394fcd0-0baa-43ae-a793-201815c3e8ce | myserver1 | ACTIVE | net1=10.0.1.3 |
| 2d604e05-9a6c-4ddb-9082-8a1fbdcc797d | myserver2 | ACTIVE | net1=10.0.1.4 |
| c7c0481c-3db8-4d7a-a948-60ce8211d585 | myserver3 | ACTIVE | net1=10.0.1.5 |
+--------------------------------------+-----------+--------+---------------+
$neutron net-list+--------------------------------------+------+--------------------------------------+
| id | name | subnets |
+--------------------------------------+------+--------------------------------------+
| 89dca1c6-c7d4-4f7a-b730-549af0fb6e34 | net1 | f6c832e3-9968-46fd-8e45-d5cf646db9d1 |
+--------------------------------------+------+--------------------------------------+Manage agents in neutron deploymentEvery agent which supports these extensions will
register itself with the neutron server when it
starts up.List all agents:$neutron agent-list+--------------------------------------+--------------------+-------+-------+----------------+
| id | agent_type | host | alive | admin_state_up |
+--------------------------------------+--------------------+-------+-------+----------------+
| 1b69828d-6a9b-4826-87cd-1757f0e27f31 | Linux bridge agent | HostA | :-) | True |
| a0c1c21c-d4f4-4577-9ec7-908f2d48622d | DHCP agent | HostA | :-) | True |
| ed96b856-ae0f-4d75-bb28-40a47ffd7695 | Linux bridge agent | HostB | :-) | True |
| f28aa126-6edb-4ea5-a81e-8850876bc0a8 | DHCP agent | HostB | :-) | True |
+--------------------------------------+--------------------+-------+-------+----------------+
The output shows information for four
agents. The alive field
shows :-) if the agent
reported its state within the period
defined by the
option in the
neutron.conf
file. Otherwise the
is xxx.List the DHCP agents that host a
specified networkIn some deployments, one DHCP agent is
not enough to hold all network data. In
addition, you must have a backup for it
even when the deployment is small. The
same network can be assigned to more than
one DHCP agent and one DHCP agent can host
more than one network.List DHCP agents that a a specified
network:$neutron dhcp-agent-list-hosting-net net1+--------------------------------------+-------+----------------+-------+
| id | host | admin_state_up | alive |
+--------------------------------------+-------+----------------+-------+
| a0c1c21c-d4f4-4577-9ec7-908f2d48622d | HostA | True | :-) |
+--------------------------------------+-------+----------------+-------+
List the networks hosted by a given DHCP
agent.This command is to show which networks a
given dhcp agent is managing.$neutron net-list-on-dhcp-agent a0c1c21c-d4f4-4577-9ec7-908f2d48622d+--------------------------------------+------+---------------------------------------------------+
| id | name | subnets |
+--------------------------------------+------+---------------------------------------------------+
| 89dca1c6-c7d4-4f7a-b730-549af0fb6e34 | net1 | f6c832e3-9968-46fd-8e45-d5cf646db9d1 10.0.1.0/24 |
+--------------------------------------+------+---------------------------------------------------+
Show agent details.The agent-list
command shows details for a specified
agent:$neutron agent-show a0c1c21c-d4f4-4577-9ec7-908f2d48622d+---------------------+----------------------------------------------------------+
| Field | Value |
+---------------------+----------------------------------------------------------+
| admin_state_up | True |
| agent_type | DHCP agent |
| alive | False |
| binary | neutron-dhcp-agent |
| configurations | { |
| | "subnets": 1, |
| | "use_namespaces": true, |
| | "dhcp_driver": "neutron.agent.linux.dhcp.Dnsmasq", |
| | "networks": 1, |
| | "dhcp_lease_time": 120, |
| | "ports": 3 |
| | } |
| created_at | 2013-03-16T01:16:18.000000 |
| description | |
| heartbeat_timestamp | 2013-03-17T01:37:22.000000 |
| host | HostA |
| id | 58f4ce07-6789-4bb3-aa42-ed3779db2b03 |
| started_at | 2013-03-16T06:48:39.000000 |
| topic | dhcp_agent |
+---------------------+----------------------------------------------------------+
In this output,
heartbeat_timestamp
is the time on the neutron server. You do
not need to synchronize all agents to this
time for this extension to run correctly.
configurations
describes the static configuration for the
agent or run time data. This agent is a
DHCP agent and it hosts one network, one
subnet, and three ports.Different types of agents show different
details. The following output shows
information for a Linux bridge
agent:$neutron agent-show ed96b856-ae0f-4d75-bb28-40a47ffd7695+---------------------+--------------------------------------+
| Field | Value |
+---------------------+--------------------------------------+
| admin_state_up | True |
| binary | neutron-linuxbridge-agent |
| configurations | { |
| | "physnet1": "eth0", |
| | "devices": "4" |
| | } |
| created_at | 2013-03-16T01:49:52.000000 |
| description | |
| disabled | False |
| group | agent |
| heartbeat_timestamp | 2013-03-16T01:59:45.000000 |
| host | HostB |
| id | ed96b856-ae0f-4d75-bb28-40a47ffd7695 |
| topic | N/A |
| started_at | 2013-03-16T06:48:39.000000 |
| type | Linux bridge agent |
+---------------------+--------------------------------------+The output shows
bridge-mapping and
the number of virtual network devices on
this L2 agent.Manage assignment of networks to DHCP agentNow that you have run the
net-list-on-dhcp-agent and
dhcp-agent-list-hosting-net
commands, you can add a network to a DHCP agent
and remove one from it.Default scheduling.When you create a network with one port,
you can schedule it to an active DHCP
agent. If many active DHCP agents are
running, select one randomly. You can
design more sophisticated scheduling
algorithms in the same way as nova-schedule later
on.$neutron net-create net2$neutron subnet-create net2 9.0.1.0/24 --name subnet2$neutron port-create net2$neutron dhcp-agent-list-hosting-net net2+--------------------------------------+-------+----------------+-------+
| id | host | admin_state_up | alive |
+--------------------------------------+-------+----------------+-------+
| a0c1c21c-d4f4-4577-9ec7-908f2d48622d | HostA | True | :-) |
+--------------------------------------+-------+----------------+-------+It is allocated to DHCP agent on HostA.
If you want to validate the behavior
through the dnsmasq
command, you must create a subnet for the
network because the DHCP agent starts the
dnsmasq service only if
there is a DHCP.Assign a network to a given DHCP
agent.To add another DHCP agent to host the
network, run this command:$neutron dhcp-agent-network-add f28aa126-6edb-4ea5-a81e-8850876bc0a8 net2Added network net2 to dhcp agent$neutron dhcp-agent-list-hosting-net net2+--------------------------------------+-------+----------------+-------+
| id | host | admin_state_up | alive |
+--------------------------------------+-------+----------------+-------+
| a0c1c21c-d4f4-4577-9ec7-908f2d48622d | HostA | True | :-) |
| f28aa126-6edb-4ea5-a81e-8850876bc0a8 | HostB | True | :-) |
+--------------------------------------+-------+----------------+-------+Both DHCP agents host the
net2
network.Remove a network from a specified DHCP
agent.This command is the sibling command for
the previous one. Remove
net2 from the DHCP
agent for HostA:$neutron dhcp-agent-network-remove a0c1c21c-d4f4-4577-9ec7-908f2d48622d net2Removed network net2 to dhcp agent$neutron dhcp-agent-list-hosting-net net2+--------------------------------------+-------+----------------+-------+
| id | host | admin_state_up | alive |
+--------------------------------------+-------+----------------+-------+
| f28aa126-6edb-4ea5-a81e-8850876bc0a8 | HostB | True | :-) |
+--------------------------------------+-------+----------------+-------+You can see that only the DHCP agent for
HostB is hosting the
net2
network.HA of DHCP agentsBoot a VM on net2. Let both DHCP agents host
net2. Fail the agents in
turn to see if the VM can still get the desired
IP.Boot a VM on net2.$neutron net-list+--------------------------------------+------+--------------------------------------------------+
| id | name | subnets |
+--------------------------------------+------+--------------------------------------------------+
| 89dca1c6-c7d4-4f7a-b730-549af0fb6e34 | net1 | f6c832e3-9968-46fd-8e45-d5cf646db9d1 10.0.1.0/24|
| 9b96b14f-71b8-4918-90aa-c5d705606b1a | net2 | 6979b71a-0ae8-448c-aa87-65f68eedcaaa 9.0.1.0/24 |
+--------------------------------------+------+--------------------------------------------------+$nova boot --image tty --flavor 1 myserver4 \
--nic net-id=9b96b14f-71b8-4918-90aa-c5d705606b1a$nova list+--------------------------------------+-----------+--------+---------------+
| ID | Name | Status | Networks |
+--------------------------------------+-----------+--------+---------------+
| c394fcd0-0baa-43ae-a793-201815c3e8ce | myserver1 | ACTIVE | net1=10.0.1.3 |
| 2d604e05-9a6c-4ddb-9082-8a1fbdcc797d | myserver2 | ACTIVE | net1=10.0.1.4 |
| c7c0481c-3db8-4d7a-a948-60ce8211d585 | myserver3 | ACTIVE | net1=10.0.1.5 |
| f62f4731-5591-46b1-9d74-f0c901de567f | myserver4 | ACTIVE | net2=9.0.1.2 |
+--------------------------------------+-----------+--------+---------------+Make sure both DHCP agents hosting
'net2'.Use the previous commands to assign the
network to agents.$neutron dhcp-agent-list-hosting-net net2+--------------------------------------+-------+----------------+-------+
| id | host | admin_state_up | alive |
+--------------------------------------+-------+----------------+-------+
| a0c1c21c-d4f4-4577-9ec7-908f2d48622d | HostA | True | :-) |
| f28aa126-6edb-4ea5-a81e-8850876bc0a8 | HostB | True | :-) |
+--------------------------------------+-------+----------------+-------+Test the HALog in to the
myserver4 VM,
and run udhcpc,
dhclient or
other DHCP client.Stop the DHCP agent on HostA.
Besides stopping the
neutron-dhcp-agent
binary, you must stop the
dnsmasq
processes.Run a DHCP client in VM to see
if it can get the wanted IP.
Stop the DHCP agent on HostB
too.Run udhcpc in
the VM; it cannot get the wanted
IP.Start DHCP agent on HostB. The
VM gets the wanted IP again.Disable and remove an agentAn administrator might want to disable an agent
if a system hardware or software upgrade is
planned. Some agents that support scheduling also
support disabling and enabling agents, such as L3
and DHCP agents. After the agent is disabled, the
scheduler does not schedule new resources to the
agent. After the agent is disabled, you can safely
remove the agent. Remove the resources on the
agent before you delete the agent.To run the following commands, you must stop the
DHCP agent on HostA.$neutron agent-update --admin-state-up False a0c1c21c-d4f4-4577-9ec7-908f2d48622d$neutron agent-list+--------------------------------------+--------------------+-------+-------+----------------+
| id | agent_type | host | alive | admin_state_up |
+--------------------------------------+--------------------+-------+-------+----------------+
| 1b69828d-6a9b-4826-87cd-1757f0e27f31 | Linux bridge agent | HostA | :-) | True |
| a0c1c21c-d4f4-4577-9ec7-908f2d48622d | DHCP agent | HostA | :-) | False |
| ed96b856-ae0f-4d75-bb28-40a47ffd7695 | Linux bridge agent | HostB | :-) | True |
| f28aa126-6edb-4ea5-a81e-8850876bc0a8 | DHCP agent | HostB | :-) | True |
+--------------------------------------+--------------------+-------+-------+----------------+$neutron agent-delete a0c1c21c-d4f4-4577-9ec7-908f2d48622dDeleted agent: a0c1c21c-d4f4-4577-9ec7-908f2d48622d$neutron agent-list+--------------------------------------+--------------------+-------+-------+----------------+
| id | agent_type | host | alive | admin_state_up |
+--------------------------------------+--------------------+-------+-------+----------------+
| 1b69828d-6a9b-4826-87cd-1757f0e27f31 | Linux bridge agent | HostA | :-) | True |
| ed96b856-ae0f-4d75-bb28-40a47ffd7695 | Linux bridge agent | HostB | :-) | True |
| f28aa126-6edb-4ea5-a81e-8850876bc0a8 | DHCP agent | HostB | :-) | True |
+--------------------------------------+--------------------+-------+-------+----------------+After deletion, if you restart the DHCP agent,
it appears on the agent list again.