457819072f
Bug #2113862 details a number of suggested corrections and additions to the Workload Stabilization doc. This patch adds those suggested changes. Closes-Bug: #2113862 Assisted-By: Cursor (claude-3.5-sonnet) Change-Id: I4131a304c064d2ea397b2447025c7edf69a56e2a Signed-off-by: Ronelle Landy <rlandy@redhat.com>
188 lines
8.4 KiB
ReStructuredText
188 lines
8.4 KiB
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===============================
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Workload Stabilization Strategy
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===============================
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Synopsis
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--------
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**display name**: ``Workload stabilization``
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**goal**: ``workload_balancing``
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.. watcher-term:: watcher.decision_engine.strategy.strategies.workload_stabilization.WorkloadStabilization
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Requirements
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------------
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Metrics
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*******
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The *workload_stabilization* strategy requires the following metrics:
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============================ ==================================================
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metric description
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============================ ==================================================
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``instance_ram_usage`` ram memory usage in an instance as float in
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megabytes
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``instance_cpu_usage`` cpu usage in an instance as float ranging between
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0 and 100 representing the total cpu usage as
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percentage
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``host_ram_usage`` ram memory usage in a compute node as float in
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megabytes
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``host_cpu_usage`` cpu usage in a compute node as float ranging
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between 0 and 100 representing the total cpu
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usage as percentage
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============================ ==================================================
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Cluster data model
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******************
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Default Watcher's Compute cluster data model:
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.. watcher-term:: watcher.decision_engine.model.collector.nova.NovaClusterDataModelCollector
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Actions
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*******
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Default Watcher's actions:
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.. list-table::
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:widths: 30 30
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:header-rows: 1
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* - action
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- description
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* - ``migration``
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- .. watcher-term:: watcher.applier.actions.migration.Migrate
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Planner
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*******
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Default Watcher's planner:
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.. watcher-term:: watcher.decision_engine.planner.weight.WeightPlanner
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Configuration
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-------------
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Strategy parameters are:
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====================== ====== =================== =============================
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parameter type default Value description
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====================== ====== =================== =============================
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``metrics`` array |metrics| Metrics used as rates of
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cluster loads.
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``thresholds`` object |thresholds| Dict where key is a metric
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and value is a trigger value.
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The strategy will only will
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look for an action plan when
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the standard deviation for
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the usage of one of the
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resources included in the
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metrics, taken as a
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normalized usage between
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0 and 1 among the hosts is
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higher than the threshold.
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The value of a perfectly
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balanced cluster for the
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standard deviation would be
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0, while in a totally
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unbalanced one would be 0.5,
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which should be the maximum
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value.
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``weights`` object |weights| These weights are used to
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calculate common standard
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deviation when optimizing
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the resources usage.
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Name of weight contains meter
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name and _weight suffix.
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Higher values imply the
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metric will be prioritized
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when calculating an optimal
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resulting cluster
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distribution.
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``instance_metrics`` object |instance_metrics| This parameter represents
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the compute node metrics
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representing compute resource
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usage for the instances
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resource indicated in the
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metrics parameter.
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``host_choice`` string retry Method of host’s choice when
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analyzing destination for
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instances.
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There are cycle, retry and
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fullsearch methods. Cycle
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will iterate hosts in cycle.
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Retry will get some hosts
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random (count defined in
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retry_count option).
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Fullsearch will return each
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host from list.
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``retry_count`` number 1 Count of random returned
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hosts.
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``periods`` object |periods| Time, in seconds, to get
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statistical values for
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resources usage for instance
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and host metrics.
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Watcher will use the last
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period to calculate resource
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usage.
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``granularity`` number 300 NOT RECOMMENDED TO MODIFY:
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The time between two measures
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in an aggregated timeseries
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of a metric.
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``aggregation_method`` object |aggn_method| NOT RECOMMENDED TO MODIFY:
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Function used to aggregate
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multiple measures into an
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aggregated value.
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====================== ====== =================== =============================
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.. |metrics| replace:: ["instance_cpu_usage", "instance_ram_usage"]
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.. |thresholds| replace:: {"instance_cpu_usage": 0.2, "instance_ram_usage": 0.2}
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.. |weights| replace:: {"instance_cpu_usage_weight": 1.0, "instance_ram_usage_weight": 1.0}
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.. |instance_metrics| replace:: {"instance_cpu_usage": "host_cpu_usage", "instance_ram_usage": "host_ram_usage"}
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.. |periods| replace:: {"instance": 720, "node": 600}
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.. |aggn_method| replace:: {"instance": 'mean', "compute_node": 'mean'}
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Efficacy Indicator
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------------------
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Global efficacy indicator:
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.. watcher-func::
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:format: literal_block
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watcher.decision_engine.goal.efficacy.specs.WorkloadBalancing.get_global_efficacy_indicator
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Other efficacy indicators of the goal are:
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- ``instance_migrations_count``: The number of VM migrations to be performed
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- ``instances_count``: The total number of audited instances in strategy
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- ``standard_deviation_after_audit``: The value of resulted standard deviation
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- ``standard_deviation_before_audit``: The value of original standard deviation
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Algorithm
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---------
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You can find description of overload algorithm and role of standard deviation
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here: https://specs.openstack.org/openstack/watcher-specs/specs/newton/implemented/sd-strategy.html
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How to use it ?
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---------------
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.. code-block:: shell
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$ openstack optimize audittemplate create \
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at1 workload_balancing --strategy workload_stabilization
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$ openstack optimize audit create -a at1 \
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-p thresholds='{"instance_ram_usage": 0.05}' \
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-p metrics='["instance_ram_usage"]'
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External Links
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--------------
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None
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