f0b8204072
As discussed at our nova meetings, reorganize the juno specs into three directories: - proposed: things proposed which weren't approved - approved: things we approved but didn't implement - implemented: things approved and implemented The first I suspect is the most controversial. I've done this because I worry about the case where a future developer wants to pick up something dropped by a previous developer, but has trouble finding previous proposed specifications on the topic. Note that the actual proposed specs for Juno are adding in a later commit. Change-Id: Idcf55ca37a83d7098dcb7c2971240c4e8fd23dc8
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This work is licensed under a Creative Commons Attribution 3.0 Unported
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License.
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http://creativecommons.org/licenses/by/3.0/legalcode
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============================================
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Strictly isolate group of hosts for an image
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============================================
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https://blueprints.launchpad.net/nova/+spec/restrict-image-isolation-with-defined-keys
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The aim of this blueprint is to improve the filter
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`AggregateImagePropertiesIsolation`
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An operator wants to schedule instances for a specific image on a
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pre-defined group of hosts. In addition, he wants to strictly isolate this
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group of hosts for the image only and accept images without key scheduled
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to other hosts.
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Problem description
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===================
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Currently with the filter `AggregateImagePropertiesIsolation` we have the
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possibility to define images that will be scheduled on a specific aggregate
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following this matrix:
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+--------------+------------+----------+----------+
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| img \\ aggr | key=foo | key=xxx | <empty> |
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+==============+============+==========+==========+
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| key=foo | True | False | True |
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+--------------+------------+----------+----------+
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| key=bar | False | False | True |
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+--------------+------------+----------+----------+
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| <empty> | True | True | True |
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+--------------+------------+----------+----------+
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*Table 1: row are image properties, col are aggregate metadata.*
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The problem is:
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* An image without key can still be scheduled in a tagged aggregate
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* The hosts outside aggregates or in a no-tagged aggregate can still accept a
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tagged image
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Proposed change
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===============
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We would like to add an option to:
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* Make tagged aggregate refuse not-tagged images
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* Make not-tagged aggregate accept ONLY not-tagged images
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+--------------+------------+----------+----------+
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| img \\ aggr | key=foo | key=xxx | <empty> |
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+==============+============+==========+==========+
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| key=foo | True | False | False |
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+--------------+------------+----------+----------+
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| key=bar | False | False | False |
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+--------------+------------+----------+----------+
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| <empty> | False | False | True |
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+--------------+------------+----------+----------+
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*Table 2: row are image properties, col are aggregate metadata*
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We propose to add global option `aggregate_image_filter_strict_isolation` in
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the filter which dictates strictness level of the isolation:
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* aggregate_image_filter_strict_isolation = False:
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the filter functions as before (Tab. 1)
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* aggregate_image_filter_strict_isolation = True:
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the filter functions as proposed decision (Tab. 2)
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*For backward compatibility this option will be set by default to False.*
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We also propose to add this option configurable in per-aggregate.
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Alternatives
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------------
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* An alternative solution would be to create a new filter that inherits from
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`AggregateImagePropertiesIsolation`.
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* A more configurable solution could be to use two config options
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`allow_untagged_images_in_tagged_aggregate=True` and
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`allow_tagged_images_in_untagged_aggregate=True` but currently we cannot
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find any cases of using this alternative.
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Data model impact
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-----------------
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None
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REST API impact
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---------------
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None
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Security impact
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---------------
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None
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Notifications impact
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--------------------
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None
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Other end user impact
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---------------------
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None
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Performance Impact
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------------------
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None
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Other deployer impact
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---------------------
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* Operator needs to update the scheduler's `nova.conf` to set the option
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`aggregate_image_filter_strict_isolation`.
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::
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aggregate_image_filter_strict_isolation=True
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* To configure per-aggregate Operator needs to set the metadata.
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::
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nova aggregate-set-metadata aggrA
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aggregate_image_filter_strict_isolation=True
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*Note: For existing system, instances will be not re-scheduled. The operator
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always have the possibility to do migration.*
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Developer impact
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----------------
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None
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Implementation
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==============
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Assignee(s)
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-----------
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Primary assignee:
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sahid-ferdjaoui
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Work Items
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----------
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* Updating `AggregateImagePropertiesIsolation` to accept the new global option.
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* Updating `AggregateImagePropertiesIsolation` to accept per-aggregate
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configuration.
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Dependencies
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============
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None
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Testing
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=======
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* Unit tests can validate the expected behavior.
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Documentation Impact
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====================
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We need to update the documentation:
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'doc/source/devref/filter_scheduler.rst'
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References
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==========
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* http://docs.openstack.org/developer/nova/devref/filter_scheduler.html#filtering
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* https://review.openstack.org/#/c/80940/
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