[OVN] Add router availability zones documentation
This patch is adding documentation about the router availability zones feature in the OVN driver. Change-Id: I6c8267100e1ee82c8b563528467b50b91f7700f6 Related-Bug: #1881095 Signed-off-by: Lucas Alvares Gomes <lucasagomes@gmail.com>
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Lucas Alvares Gomes
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@ -14,3 +14,4 @@ OVN Driver Administration Guide
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dpdk
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troubleshooting
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sriov
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router_availability_zones
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208
doc/source/admin/ovn/router_availability_zones.rst
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208
doc/source/admin/ovn/router_availability_zones.rst
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@ -0,0 +1,208 @@
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.. _ovn_router_availability_zones:
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=======================================
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Router Availability Zones guide for OVN
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=======================================
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The purpose of this page is to describe how the router availability zones
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works with OVN. Prior to reading this document, it is recommended to first
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read :ref:`ML2/OVS driver Availability Zones guide<config-az>`.
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How to configure it
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~~~~~~~~~~~~~~~~~~~
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Different from the ML2/OVS driver for Neutron the availability zones for
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the OVN driver is not configured via a configuration file. Since ML2/OVN
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does not rely on an external agent such as the L3 agent, certain nodes
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(e.g gateway/networker node) won't have any Neutron configuration file present. For
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this reason, OVN uses the local OVSDB for configuring the availability
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zones that instance of ``ovn-controller`` running on that hypervisor
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belongs to.
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The configuration is done via the ``ovn-cms-options`` entry in
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*external_ids* column of the local *Open_vSwitch* table:
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.. code-block:: bash
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$ ovs-vsctl set Open_vSwitch . external-ids:ovn-cms-options="enable-chassis-as-gw,availability-zones=az-0:az-1:az-2"
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.. end
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The above command is adding two configurations to the ``ovn-cms-options``
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option, the ``enable-chassis-as-gw`` option which tells the OVN driver
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that this is a gateway/networker node and the ``availability-zones``
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option specifying three availability zones: **az-0**, **az-1** and
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**az-2**.
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Note that, the syntax used to specify the availability zones is the
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``availability-zones`` word, followed by an equal sign (=) and a
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**colon** separated list of the availability zones that this local
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``ovn-controller`` instance belongs to.
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To confirm the specific ``ovn-controller`` availability zones, check the
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**Availability Zone** column in the output of the command below:
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.. code-block:: bash
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$ openstack network agent list
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+--------------------------------------+------------------------------+----------------+-------------------+-------+-------+----------------+
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| ID | Agent Type | Host | Availability Zone | Alive | State | Binary |
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+--------------------------------------+------------------------------+----------------+-------------------+-------+-------+----------------+
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| 2d1924b2-99a4-4c6c-a4f2-0be64c0cec8c | OVN Controller Gateway agent | gateway-host-0 | az0, az1, az2 | :-) | UP | ovn-controller |
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+--------------------------------------+------------------------------+----------------+-------------------+-------+-------+----------------+
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.. end
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.. note::
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If you know the UUID of the agent the "**openstack network agent show
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<UUID>**" command can also be used.
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.. end
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To confirm the availability zones defined in the system as a whole:
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.. code-block:: bash
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$ openstack availability zone list
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+-----------+-------------+
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| Zone Name | Zone Status |
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+-----------+-------------+
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| az0 | available |
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| az1 | available |
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| az2 | available |
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+-----------+-------------+
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.. end
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Using router availability zones
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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In order to create a router with availability zones the
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``--availability-zone-hint`` should be passed to the create command,
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note that this parameter can be specified multiple times in case the
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router belongs to more than one availability zone. For example:
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.. code-block:: bash
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$ openstack router create --availability-zone-hint az-0 --availability-zone-hint az-1 router-0
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+-------------------------+--------------------------------------+
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| Field | Value |
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+-------------------------+--------------------------------------+
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| admin_state_up | UP |
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| availability_zone_hints | az-0, az-1 |
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| availability_zones | |
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| created_at | 2020-06-04T08:29:33Z |
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| description | |
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| external_gateway_info | null |
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| flavor_id | None |
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| id | 8fd6d01a-57ad-4e91-a788-ebe48742d000 |
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| name | router-0 |
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| project_id | 2a364ced6c084888be0919450629de1c |
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| revision_number | 1 |
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| routes | |
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| status | ACTIVE |
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| tags | |
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| updated_at | 2020-06-04T08:29:33Z |
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+-------------------------+--------------------------------------+
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.. end
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It's also possible to set the default availability zones via the
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*/etc/neutron/neutron.conf* configuration file:
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.. code-block:: ini
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[DEFAULT]
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default_availability_zones = az-0,az-2
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...
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.. end
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When scheduling the gateway ports of a router, the OVN driver will take
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into consideration the router availability zones and make sure that the
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ports are scheduled on the nodes belonging to those availability zones.
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Note that in the router object we have two attributes
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related to availability zones: ``availability_zones`` and
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``availability_zone_hints``:
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.. code-block:: bash
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| availability_zone_hints | az-0, az-1 |
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| availability_zones | |
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.. end
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This distinction makes more sense in the **ML2/OVS** driver which
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relies on the L3 agent for its router placement (see the :ref:`ML2/OVS
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driver Availability Zones guide<config-az>` for more information). In
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**ML2/OVN** the ``ovn-controller`` service will be running on all nodes
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of the cluster so the ``availability_zone_hints`` will always match the
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``availability_zones`` attribute.
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OVN Database information
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~~~~~~~~~~~~~~~~~~~~~~~~
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In order to check the availability zones of a router
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via the OVN Northbound database, one can look for the
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``neutron:availability_zone_hints`` key in the ``external_ids``
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column for its entry in the ``Logical_Router`` table:
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.. code-block:: bash
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$ ovn-nbctl list Logical_Router
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_uuid : 4df68f1e-17dd-4b9a-848d-b6152ae19203
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external_ids : {"neutron:availability_zone_hints"="az-0,az-1", "neutron:gw_port_id"="", "neutron:revision_number"="1", "neutron:router_name"=router-0}
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name : neutron-8fd6d01a-57ad-4e91-a788-ebe48742d000
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...
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.. end
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To check the availability zones of the Chassis, look at the
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``ovn-cms-options`` key in the ``other_config`` column (or
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``external_ids`` for an older version of OVN) of the ``Chassis`` table
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in the OVN Southbound database:
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.. code-block:: bash
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$ ovn-sbctl list Chassis
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_uuid : abaa9f07-9988-40c0-bd1a-8d8326af08b0
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name : "2d1924b2-99a4-4c6c-a4f2-0be64c0cec8c"
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other_config : {..., ovn-cms-options="enable-chassis-as-gw,availability-zones=az-0:az-1:az-2"}
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...
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.. end
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As mentioned in the `Using router availability zones`_ section, the
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scheduling of the gateway router ports will take into consideration
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the availability zones that the router belongs to. We can confirm
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this behavior by looking in the ``Gateway_Chassis`` table from the OVN
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Southbound database:
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.. code-block:: bash
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$ ovn-sbctl list Gateway_Chassis
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_uuid : ac61b70f-ff51-43d9-830b-f9bc6d74090a
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chassis_name : "2d1924b2-99a4-4c6c-a4f2-0be64c0cec8c"
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external_ids : {}
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name : lrp-5a40eeca-5233-4029-a470-9018aa8b3de9_2d1924b2-99a4-4c6c-a4f2-0be64c0cec8c
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options : {}
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priority : 2
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_uuid : c1b7763b-1784-4e5a-a948-853662faeddc
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chassis_name : "1cde2542-69f9-4598-b20b-d4f68304deb0"
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external_ids : {}
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name : lrp-5a40eeca-5233-4029-a470-9018aa8b3de9_1cde2542-69f9-4598-b20b-d4f68304deb0
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options : {}
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priority : 1
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.. end
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Each entry on this table represents an instance of the gateway port
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(L3 HA, for more information see :ref:`Routing in OVN<ovn_routing>`),
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the ``chassis_name`` column indicates which Chassis that port instance
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is scheduled onto. If we co-relate each entry and their ``chassis_name``
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we will see that this port has been only scheduled to Chassis matching
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with the router's availability zones.
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