8354f42e20
This counts instance mappings for counting quota usage for instances
and adds calls to placement for counting quota usage for cores and ram.
During an upgrade, if any un-migrated instance mappings are found (with
NULL user_id or NULL queued_for_delete fields), we will fall back to
the legacy counting method.
Counting quota usage from placement is opt-in via the
[quota]count_usage_from_placement configuration option because:
* Though beneficial for multi-cell deployments to be resilient to
down cells, the vast majority of deployments are single cell and
will not be able to realize a down cells resiliency benefit and may
prefer to keep legacy quota usage counting.
* Usage for resizes will reflect resources being held on both the
source and destination until the resize is confirmed or reverted.
Operators may not want to enable counting from placement based on
whether the behavior change is problematic for them.
* Placement does not yet support the ability to partition resource
providers from mulitple Nova deployments, so environments that are
sharing a single placement deployment would see usage that
aggregates all Nova deployments together. Such environments should
not enable counting from placement.
* Usage for unscheduled instances in ERROR state will not reflect
resource consumption for cores and ram because the instance has no
placement allocations.
* Usage for instances in SHELVED_OFFLOADED state will not reflect
resource consumption for cores and ram because the instance has no
placement allocations. Note that because of this, it will be possible for a
request to unshelve a server to be rejected if the user does not have
enough quota available to support the cores and ram needed by the server to
be unshelved.
Part of blueprint count-quota-usage-from-placement
Change-Id: Ie22b0acb5824a41da327abdcf9848d02fc9a92f5
50 lines
2.8 KiB
YAML
50 lines
2.8 KiB
YAML
upgrade:
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- |
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It is now possible to count quota usage for cores and ram from the
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placement service and instances from instance mappings in the API database
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instead of counting resources from cell databases. This makes quota usage
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counting resilient in the presence of down or poor-performing cells.
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Quota usage counting from placement is opt-in via the
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``[quota]count_usage_from_placement`` configuration option.
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There are some things to note when opting in to counting quota usage from
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placement:
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* Counted usage will not be accurate in an environment where multiple Nova
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deployments are sharing a placement deployment because currently
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placement has no way of partitioning resource providers between different
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Nova deployments. Operators who are running multiple Nova deployments
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that share a placement deployment should not set the
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``[quota]count_usage_from_placement`` configuration option to ``True``.
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* Behavior will be different for resizes. During a resize, resource
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allocations are held on both the source and destination (even on the same
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host, see https://bugs.launchpad.net/nova/+bug/1790204) until the resize
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is confirmed or reverted. Quota usage will be inflated for servers in
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the ``VERIFY_RESIZE`` state and operators should weigh the advantages and
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disadvantages before enabling ``[quota]count_usage_from_placement``.
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* The ``populate_queued_for_delete`` and ``populate_user_id`` online data
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migrations must be completed before usage can be counted from placement.
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Until the data migration is complete, the system will fall back to legacy
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quota usage counting from cell databases depending on the result of an
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``EXISTS`` database query during each quota check, if
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``[quota]count_usage_from_placement`` is set to ``True``. Operators who
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want to avoid the performance hit from the ``EXISTS`` queries should wait
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to set the ``[quota]count_usage_from_placement`` configuration option to
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``True`` until after they have completed their online data migrations via
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``nova-manage db online_data_migrations``.
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* Behavior will be different for unscheduled servers in ``ERROR`` state.
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A server in ``ERROR`` state that has never been scheduled to a compute
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host will not have placement allocations, so it will not consume quota
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usage for cores and ram.
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* Behavior will be different for servers in ``SHELVED_OFFLOADED`` state.
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A server in ``SHELVED_OFFLOADED`` state will not have placement
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allocations, so it will not consume quota usage for cores and ram. Note
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that because of this, it will be possible for a request to unshelve a
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server to be rejected if the user does not have enough quota available to
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support the cores and ram needed by the server to be unshelved.
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