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=============================================
Watcher Overload standard deviation algorithm
=============================================
Synopsis
--------
**display name**: ``Workload stabilization``
**goal**: ``workload_balancing``
.. watcher-term:: watcher.decision_engine.strategy.strategies.workload_stabilization.WorkloadStabilization
Requirements
------------
Metrics
*******
The *workload_stabilization* strategy requires the following metrics:
============================ ============ ======= =============================
metric service name plugins comment
============================ ============ ======= =============================
``compute.node.cpu.percent`` ceilometer_ none need to set the
``compute_monitors`` option
to ``cpu.virt_driver`` in the
nova.conf.
``hardware.memory.used`` ceilometer_ SNMP_
``cpu`` ceilometer_ none
``instance_ram_usage`` ceilometer_ none
============================ ============ ======= =============================
.. _ceilometer: https://docs.openstack.org/ceilometer/latest/admin/telemetry-measurements.html#openstack-compute
.. _SNMP: https://docs.openstack.org/ceilometer/latest/admin/telemetry-measurements.html#snmp-based-meters
Cluster data model
******************
Default Watcher's Compute cluster data model:
.. watcher-term:: watcher.decision_engine.model.collector.nova.NovaClusterDataModelCollector
Actions
*******
Default Watcher's actions:
.. list-table::
:widths: 30 30
:header-rows: 1
* - action
- description
* - ``migration``
- .. watcher-term:: watcher.applier.actions.migration.Migrate
Planner
*******
Default Watcher's planner:
.. watcher-term:: watcher.decision_engine.planner.weight.WeightPlanner
Configuration
-------------
Strategy parameters are:
==================== ====== ===================== =============================
parameter type default Value description
==================== ====== ===================== =============================
``metrics`` array |metrics| Metrics used as rates of
cluster loads.
``thresholds`` object |thresholds| Dict where key is a metric
and value is a trigger value.
``weights`` object |weights| These weights used to
calculate common standard
deviation. Name of weight
contains meter name and
_weight suffix.
``instance_metrics`` object |instance_metrics| Mapping to get hardware
statistics using instance
metrics.
``host_choice`` string retry Method of host's choice.
There are cycle, retry and
fullsearch methods. Cycle
will iterate hosts in cycle.
Retry will get some hosts
random (count defined in
retry_count option).
Fullsearch will return each
host from list.
``retry_count`` number 1 Count of random returned
hosts.
``periods`` object |periods| These periods are used to get
statistic aggregation for
instance and host metrics.
The period is simply a
repeating interval of time
into which the samples are
grouped for aggregation.
Watcher uses only the last
period of all received ones.
==================== ====== ===================== =============================
.. |metrics| replace:: ["instance_cpu_usage", "instance_ram_usage"]
.. |thresholds| replace:: {"instance_cpu_usage": 0.2, "instance_ram_usage": 0.2}
.. |weights| replace:: {"instance_cpu_usage_weight": 1.0, "instance_ram_usage_weight": 1.0}
.. |instance_metrics| replace:: {"instance_cpu_usage": "compute.node.cpu.percent", "instance_ram_usage": "hardware.memory.used"}
.. |periods| replace:: {"instance": 720, "node": 600}
Efficacy Indicator
------------------
.. watcher-func::
:format: literal_block
watcher.decision_engine.goal.efficacy.specs.ServerConsolidation.get_global_efficacy_indicator
Algorithm
---------
You can find description of overload algorithm and role of standard deviation
here: https://specs.openstack.org/openstack/watcher-specs/specs/newton/implemented/sd-strategy.html
How to use it ?
---------------
.. code-block:: shell
$ openstack optimize audittemplate create \
at1 workload_balancing --strategy workload_stabilization
$ openstack optimize audit create -a at1 \
-p thresholds='{"instance_ram_usage": 0.05}' \
-p metrics='["instance_ram_usage"]'
External Links
--------------
- `Watcher Overload standard deviation algorithm spec <https://specs.openstack.org/openstack/watcher-specs/specs/newton/implemented/sd-strategy.html>`_
|
