208 lines
5.5 KiB
ReStructuredText
208 lines
5.5 KiB
ReStructuredText
..
|
|
This work is licensed under a Creative Commons Attribution 3.0 Unported
|
|
License.
|
|
|
|
http://creativecommons.org/licenses/by/3.0/legalcode
|
|
|
|
======================================
|
|
Scheduling support for Routed Networks
|
|
======================================
|
|
|
|
https://blueprints.launchpad.net/nova/+spec/routed-networks-scheduling
|
|
|
|
Neutron provides network segments support thanks to Routed Networks where you
|
|
can create a port allocated to a specific segment. Unfortunately, Nova doesn't
|
|
verify the segment at every instance operation, including those where you move
|
|
an instance, which leads to inconsistencies.
|
|
|
|
|
|
Problem description
|
|
===================
|
|
|
|
Although it's possible to create a Neutron port with a routed networks setup
|
|
and boot an instance with this port, the network locality of the compute node
|
|
associated with the instance won't be verified by the scheduler and could
|
|
lead to a wrong scheduling decision. This is problematic when a move operation
|
|
sends an instance to a compute node that isn't in the network segment that is
|
|
related to the IP address that was allocated at boot time.
|
|
|
|
As a result of this gap, the only way to use routed networks in Nova currently
|
|
is by creating a port having the ``ip_allocation`` value be ``deferred`` and
|
|
making sure that all compute services are assigned to at least one network
|
|
segment.
|
|
|
|
Use Cases
|
|
---------
|
|
|
|
As an operator, I'd like to make sure that instances IP addresses can be
|
|
correctly separated between the network segments I provided.
|
|
|
|
As an operator, I don't want to see instances going to compute services that
|
|
aren't in network segments if the user asks for either a port or a routed
|
|
network.
|
|
|
|
As a user, I'd like Nova to place my instance on the correct host according to
|
|
the port or network I've requested for my instance, without having to
|
|
specifically create a port with a ``ip_allocation=deferred`` value.
|
|
|
|
|
|
Proposed change
|
|
===============
|
|
|
|
Once you `configure routed networks in Neutron`_, network segments are
|
|
represented as Placement Resource Providers. Neutron will then ask Nova to
|
|
create a Nova host aggregate for each segment and will add compute services
|
|
that are mapped with respective segments into the related aggregates.
|
|
Eventually, Nova will mirror those aggregates into Placement aggregates.
|
|
|
|
What we then need for Nova is to have a way for asking the Placement API to
|
|
only get resource providers (i.e. compute nodes) that are in the aggregate
|
|
related to the segments that are in the network passed by the user (or related
|
|
to the port that is asked).
|
|
|
|
As Nova needs to find which segments are related and then which aggregates,
|
|
we could just provide a new pre-filter that would look at it if some
|
|
configuration option (say ``query_placement_for_routed_network_aggregates``)
|
|
would be ``True``.
|
|
|
|
A pseudo-code for it would be :
|
|
|
|
.. code::
|
|
|
|
def support_routed_networks(ctxt, request_spec):
|
|
if not CONF.query_placement_for_routed_network_aggregates:
|
|
return False
|
|
segment_ids = <get_all_segments_ids_from_network_or_port>
|
|
for segment in segment_ids:
|
|
agg_info = <get_provider_aggregates_from_segment_id>
|
|
<append_agg_info_to_required_aggregates>
|
|
|
|
.. note::
|
|
|
|
As said below in the `Alternatives`_ section, we could have Neutron passing
|
|
directly the aggregates, so this pre-filter could be deprecated once we
|
|
do it.
|
|
|
|
|
|
Alternatives
|
|
------------
|
|
|
|
Instead of having a new pre-filter, we could provide a specific scheduler
|
|
filter. This said, given we limit the number of allocation candidates returned
|
|
by Placement, we could miss some good resource providers so the filter couldn't
|
|
work.
|
|
|
|
Another alternative would be to have Neutron passing directly the needed
|
|
aggregate to Nova instead of Nova asking Neutron for it, but that would mean
|
|
that we should modify Neutron to return the Placement needed query in the
|
|
``port.resource_request`` attribute.
|
|
|
|
Data model impact
|
|
-----------------
|
|
|
|
We may need to augment the ``RequestSpec`` object to be able to provide in its
|
|
nested ``RequestLevelParams`` object attribute the specific aggregate.
|
|
|
|
REST API impact
|
|
---------------
|
|
None.
|
|
|
|
Security impact
|
|
---------------
|
|
|
|
None.
|
|
|
|
Notifications impact
|
|
--------------------
|
|
|
|
None.
|
|
|
|
Other end user impact
|
|
---------------------
|
|
|
|
None.
|
|
|
|
Performance Impact
|
|
------------------
|
|
|
|
There could be a performance impact if we would verify the segments for every
|
|
instance in every cloud, but given we ask the operator to modify an option
|
|
if they want to use routed networks, we don't really think this would be an
|
|
issue.
|
|
|
|
Other deployer impact
|
|
---------------------
|
|
|
|
A new configuration option would be::
|
|
|
|
cfg.BoolOpt("query_placement_for_routed_network_aggregates",
|
|
default=False),
|
|
|
|
Developer impact
|
|
----------------
|
|
|
|
None.
|
|
|
|
Upgrade impact
|
|
--------------
|
|
|
|
None.
|
|
|
|
|
|
Implementation
|
|
==============
|
|
|
|
Assignee(s)
|
|
-----------
|
|
|
|
Primary assignee:
|
|
bauzas
|
|
|
|
Other contributors:
|
|
None
|
|
|
|
Feature Liaison
|
|
---------------
|
|
|
|
bauzas
|
|
|
|
Work Items
|
|
----------
|
|
|
|
* Create a new pre-filter that would find the related aggregate
|
|
* Pass the aggregate to the RequestSpec asking to verify it by Placement
|
|
* That's it.
|
|
|
|
Dependencies
|
|
============
|
|
|
|
None.
|
|
|
|
Testing
|
|
=======
|
|
|
|
Functional tests of course, but Tempest tests would be nice as well.
|
|
|
|
Documentation Impact
|
|
====================
|
|
|
|
Maybe modifying https://docs.openstack.org/neutron/latest/admin/config-routed-networks.html
|
|
|
|
References
|
|
==========
|
|
|
|
None.
|
|
|
|
.. _`configure routed networks in Neutron`: https://docs.openstack.org/neutron/latest/admin/config-routed-networks.html
|
|
|
|
History
|
|
=======
|
|
|
|
.. list-table:: Revisions
|
|
:header-rows: 1
|
|
|
|
* - Release Name
|
|
- Description
|
|
* - Victoria
|
|
- Introduced
|