4e325088d3
This patch adds the documentation to the Network Availability Zones support in OVN. Instead of having two documentation pages, one for router AZs and another one for network AZs, this patch merges both guides into one single documentation. Setting up AZs in OVN is the same for both types and the differences between the two are documented within their own sections. The patch also removes a limitation listed in the SR-IOV documentation for OVN since we no longer have a default HA Chassis Group. This limitation was removed as part of the Network AZ work. Change-Id: I55f27a5473dcd1e6e2255007108c2008acfb6dec Signed-off-by: Lucas Alvares Gomes <lucasagomes@gmail.com>
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374 lines
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ReStructuredText
.. _ovn_availability_zones:
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================================
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Availability Zones guide for OVN
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================================
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The purpose of this page is to describe how the availability zones works
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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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There are two types of availability zones available in Neutron: Router
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and Network. For ML2/OVS, this is related to the scheduling of the L3
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agent and DHCP agent respectively. For ML2/OVN, it's about the scheduling
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of logical router ports and "external" ports respectively.
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More details about each type of availability zones can be found later
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in this document but first let's go over the common parts between them:
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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
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present. For this reason, OVN uses the local OVSDB for configuring the
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availability zones that instance of ``ovn-controller`` running on that
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hypervisor 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::
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Specifying the "enable-chassis-as-gw" option is not required for the
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Availability Zones **however** ML2/OVN will only consider nodes that
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are gateway (the ones with the "enable-chassis-as-gw" option) when
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scheduling both ``router`` and ``external`` ports. So, even tho the
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"availability-zones" option can be set own their own, the ML2/OVN
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driver does not have a use case for it at the moment.
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.. end
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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 --network
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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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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, as below:
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.. code-block:: bash
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| availability_zone_hints | az-0, az-1 |
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| availability_zones | az-0, az-1 |
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.. end
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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 `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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Northbound database:
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.. code-block:: bash
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$ ovn-nbctl 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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Network Availability Zones
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--------------------------
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Since OVN has a distributed DHCP server model (see the
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`ovn-architecture <http://www.openvswitch.org/support/dist-docs-2.5/ovn-architecture.7.html>`_
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document for more information), one may think that there's no need
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for Ml2/OVN to support Network Availability Zones as there's no need
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to co-locate a DHCP agent within the same zones to serve the VMs but,
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in ML2/OVN there's a special case which are the ``external`` ports and
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those need to be aware of the Availability Zones for its scheduling.
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These ``external`` ports are ports that are located on a different
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node than the one that the VM is running. At the moment, ML2/OVN only
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supports one case that makes use of these ports which is the :ref:`SR-IOV
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support<ovn_sriov>`.
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In order to create a network 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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network belongs to more than one availability zone. For example:
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.. code-block:: bash
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$ openstack network create --availability-zone-hint az-0 --availability-zone-hint az-1 network-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 | 2021-04-26T14:04:51Z |
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| description | |
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| dns_domain | |
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| id | ba584cdb-b866-4744-85d3-6e38718055cc |
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| ipv4_address_scope | None |
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| ipv6_address_scope | None |
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| is_default | False |
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| is_vlan_transparent | None |
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| mtu | 1442 |
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| name | network-0 |
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| port_security_enabled | True |
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| project_id | ffd9e4a60af34b0599f1d50aed20dde0 |
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| provider:network_type | None |
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| provider:physical_network | None |
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| provider:segmentation_id | None |
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| qos_policy_id | None |
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| revision_number | 1 |
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| router:external | Internal |
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| segments | None |
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| shared | False |
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| status | ACTIVE |
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| subnets | |
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| tags | |
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| updated_at | 2021-04-26T14:04:52Z |
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+---------------------------+--------------------------------------+
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.. end
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OVN Database information
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************************
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Upon creating the first ``external`` port to a network with Availability
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Zones set a HA Chassis Group correspondent to that network will also be
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created in the OVN Northbound Database:
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.. code-block:: bash
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$ openstack port create --network network-0 --vnic-type direct port-0
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+-------------------------+--------------------------------------+
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| Field | Value |
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+-------------------------+--------------------------------------+
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| id | 2523d7f5-c7ca-40b8-83c5-ac37e5b126ea |
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| name | port-0 |
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| network_id | ba584cdb-b866-4744-85d3-6e38718055cc |
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...
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+-------------------------+--------------------------------------+
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.. end
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To find the corresponding HA Chassis Group we need to look for a group
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named as *neutron-<Neutron Network UUID>*, for example:
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.. code-block:: bash
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$ ovn-nbctl list HA_Chassis_Group neutron-ba584cdb-b866-4744-85d3-6e38718055cc
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_uuid : f6a49abb-dc97-4e2a-955a-6f8e8be4865e
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external_ids : {"neutron:availability_zone_hints"="az-0,az-1"}
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ha_chassis : [46850075-7383-4da9-b0b2-5ded2858f681, ce1da6a5-77d3-4945-b218-c0ae35403b80]
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name : neutron-ba584cdb-b866-4744-85d3-6e38718055cc
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.. end
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In the output above is possible to see that the HA Chassis Group for
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the Neutron network ``ba584cdb-b866-4744-85d3-6e38718055cc`` includes
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two Chassis (the ``ha_chassis`` column) that are part of the Availability
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Zones that this network is also part of.
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We can inspect these members to see which one has the **highest**
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priority, which means that when the ``external`` port is bound it
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will first bound to the HA Chassis with the **highest** priority in
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the Group. In case that Chassis goes down the port will move on to the
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next Chassis with the **highest** priority and so on. To check these HA
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Chassis do:
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.. code-block:: bash
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$ ovn-nbctl list HA_Chassis 46850075-7383-4da9-b0b2-5ded2858f681
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_uuid : 46850075-7383-4da9-b0b2-5ded2858f681
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chassis_name : "2c5c4479-0e2b-4742-a1d7-df10be020143"
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external_ids : {}
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priority : 32766
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$ ovn-nbctl list HA_Chassis ce1da6a5-77d3-4945-b218-c0ae35403b8
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_uuid : ce1da6a5-77d3-4945-b218-c0ae35403b80
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chassis_name : "159970f0-71f7-4d3d-9a9e-92e37c5f03c5"
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external_ids : {}
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priority : 32767
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.. end
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In this case, the **active** Chassis is the
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``159970f0-71f7-4d3d-9a9e-92e37c5f03c5``.
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And lastly, to find which HA Chassis Group an external
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port belongs to by looking into the OVN Northbound Database do:
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.. code-block:: bash
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$ sudo ovn-nbctl list Logical_Switch_Port 2523d7f5-c7ca-40b8-83c5-ac37e5b126ea
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_uuid : 382d8cd8-575f-4a3f-93ba-a01cb9c2c265
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ha_chassis_group : f6a49abb-dc97-4e2a-955a-6f8e8be4865e
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name : "2523d7f5-c7ca-40b8-83c5-ac37e5b126ea"
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type : external
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...
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.. end
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The ``ha_chassis_group`` column will point to the UUID (in the OVN
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database) of the HA Chassis Group it belongs to.
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