watcher/doc/source/strategies/workload-stabilization.rst

Watcher Overload standard deviation algorithm

Synopsis

display name: Workload stabilization

goal: workload_balancing

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 hardware.memory.used	ceilometer ceilometer	none SNMP	need to set the compute_monitors option to cpu.virt_driver in the nova.conf.
cpu_util memory.resident	ceilometer ceilometer	none none	cpu_util has been removed since Stein.

Cluster data model

Default Watcher's Compute cluster data model:

watcher.decision_engine.model.collector.nova.NovaClusterDataModelCollector

Actions

Default Watcher's actions:

action	description
migration	watcher.applier.actions.migration.Migrate

Planner

Default Watcher's planner:

watcher.decision_engine.planner.weight.WeightPlanner

Configuration

Strategy parameters are:

parameter	type	default Value	description
metrics	array	["cpu_util", "memory.resident"]	Metrics used as rates of cluster loads.
thresholds	object	{"cpu_util": 0.2, "memory.resident": 0.2}	Dict where key is a metric and value is a trigger value.
weights	object	{"cpu_util_weight": 1.0, "memory.resident_weight": 1.0}	These weights used to calculate common standard deviation. Name of weight contains meter name and _weight suffix.
instance_metrics	object	{"cpu_util": "compute.node.cpu.percent", "memory.resident": "hardware.memory.used"}	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	{"instance": 720, "node": 600}	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.

Efficacy Indicator

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 ?

$ openstack optimize audittemplate create \
  at1 workload_balancing --strategy workload_stabilization

$ openstack optimize audit create -a at1 \
  -p thresholds='{"memory.resident": 0.05}' \
  -p metrics='["memory.resident"]'

External Links

• Watcher Overload standard deviation algorithm spec