Strategy Plugins

Strategy plugins are used by the autoscaler to implement the logic of scaling strategy. They typically consume metrics from the configured APM plugin and the current scaling value from the target plugin and compute a new desired value for the scaling target.

For a real-world example of a Nomad strategy plugin implementation, see the target-value plugin.

Authoring Strategy Plugins

Authoring a strategy plugin in Go can be accomplished by implementing the strategy.Strategy interface, alongside a main package to launch the plugin.

The no-op Strategy plugin can be used as a starting point for new Strategy plugins.

Strategy Plugin API

The base plugin interface must be implemented in addition to the following functions.

Run(eval *sdk.ScalingCheckEvaluation, count int64) (*sdk.ScalingCheckEvaluation, error)

The Run function is called by the agent during policy evaluation. The eval argument contains information about the current policy evaluation, including the policy specification and the metrics from the APM. The count argument includes the current value of the scaling target. The returned struct should include the result from applying the strategy.