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Merge "Add docs for compute capabilities as traits"

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Zuul 2019-03-20 05:09:12 +00:00 committed by Gerrit Code Review
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doc/source/admin/configuration/schedulers.rst
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@ -307,6 +307,8 @@ features in some virt drivers and querying traits is efficient. For more detail,
:ref:`Forbidden traits <extra-specs-forbidden-traits>` and
`Report CPU features to the Placement service <https://specs.openstack.org/openstack/nova-specs/specs/rocky/approved/report-cpu-features-as-traits.html>`_.
Also refer to `Compute capabilities as traits`_.
.. _ComputeFilter:
ComputeFilter
@ -1037,6 +1039,8 @@ nova service-disable [--reason <reason>] <id>
ERROR: Policy doesn't allow compute_extension:hosts to be performed. (HTTP 403) (Request-ID: req-ef2400f6-6776-4ea3-b6f1-7704085c27d1)
.. _config-sch-for-aggs:
Configure scheduler to support host aggregates
----------------------------------------------
@ -1449,3 +1453,72 @@ related commands. To enable or disable a cell, use
:command:`nova-manage cell_v2 update_cell` and to create pre-disabled cells,
use :command:`nova-manage cell_v2 create_cell`. See the
:ref:`man-page-cells-v2` man page for details on command usage.
Compute capabilities as traits
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Starting with the 19.0.0 Stein release, the ``nova-compute`` service will
report certain ``COMPUTE_*`` traits based on its compute driver capabilities
to the placement service. The traits will be associated with the resource
provider for that compute service. These traits can be used during scheduling
by configuring flavors with
:ref:`Required traits <extra-specs-required-traits>` or
:ref:`Forbidden traits <extra-specs-forbidden-traits>`. For example, if you
have a host aggregate with a set of compute nodes that support multi-attach
volumes, you can restrict a flavor to that aggregate by adding the
``trait:COMPUTE_VOLUME_MULTI_ATTACH=required`` extra spec to the flavor and
then restrict the flavor to the aggregate
:ref:`as normal <config-sch-for-aggs>`.
Here is an example of a libvirt compute node resource provider that is
exposing some CPU features as traits, driver capabilities as traits, and a
custom trait denoted by the ``CUSTOM_`` prefix:
.. code-block:: console
$ openstack --os-placement-api-version 1.6 resource provider trait list \
> d9b3dbc4-50e2-42dd-be98-522f6edaab3f --sort-column name
+---------------------------------------+
| name |
+---------------------------------------+
| COMPUTE_DEVICE_TAGGING |
| COMPUTE_NET_ATTACH_INTERFACE |
| COMPUTE_NET_ATTACH_INTERFACE_WITH_TAG |
| COMPUTE_TRUSTED_CERTS |
| COMPUTE_VOLUME_ATTACH_WITH_TAG |
| COMPUTE_VOLUME_EXTEND |
| COMPUTE_VOLUME_MULTI_ATTACH |
| CUSTOM_IMAGE_TYPE_RBD |
| HW_CPU_X86_MMX |
| HW_CPU_X86_SSE |
| HW_CPU_X86_SSE2 |
| HW_CPU_X86_SVM |
+---------------------------------------+
**Rules**
There are some rules associated with capability-defined traits.
1. The compute service "owns" these traits and will add/remove them when the
``nova-compute`` service starts and when the ``update_available_resource``
periodic task runs, with run intervals controlled by config option
:oslo.config:option:`update_resources_interval`.
2. The compute service will not remove any custom traits set on the resource
provider externally, such as the ``CUSTOM_IMAGE_TYPE_RBD`` trait in the
example above.
3. If compute-owned traits are removed from the resource provider externally,
for example by running ``openstack resource provider trait delete <rp_uuid>``,
the compute service will add its traits again on restart or SIGHUP.
4. If a compute trait is set on the resource provider externally which is not
supported by the driver, for example by adding the ``COMPUTE_VOLUME_EXTEND``
trait when the driver does not support that capability, the compute service
will automatically remove the unsupported trait on restart or SIGHUP.
5. Compute capability traits are standard traits defined in the `os-traits`_
library.
.. _os-traits: http://git.openstack.org/cgit/openstack/os-traits/tree/os_traits/compute