diff --git a/website/content/tools/autoscaling/plugins/strategy/target-value.mdx b/website/content/tools/autoscaling/plugins/strategy/target-value.mdx index 7be659517..41c9c24e0 100644 --- a/website/content/tools/autoscaling/plugins/strategy/target-value.mdx +++ b/website/content/tools/autoscaling/plugins/strategy/target-value.mdx @@ -6,9 +6,36 @@ description: The "target-value" strategy plugin tracks a target metric value. # Target Value Strategy Plugin -The `target-value` strategy plugin will perform count calculations in order to +The `target-value` strategy plugin performs count calculations in order to keep the value resulting from the APM query at or around a specified target. +It accomplishes this by extrapolating the current metric value and used +capacity linearly to determine if a scaling action is required and how many +instances need to be added or removed. More specify, the new scaling value is +calculated as: + +``` +new_count = (current_metric_value / target) * current_count +``` + +As an example, a policy that tracks memory usage with target defined as `70` +(representing 70% of memory usage) and there are `10` instances running will +generate a scaling action to add `2` new instances when the metric reaches `80` +(80% of memory usage) because: + +``` +new_count = (80/70) * 10 = 11.43 ~= 12 +``` + +In other words, if with 10 instances the memory usage in 80%, it's expected +that with 12 instances the memory usage is lower and closer to the target value +of 70%. + +~> **Note:** In some situations this inverse relationship may not be true, + meaning that _more_ instances causes the metric value to _grow_. Make sure + you have a good grasp of your query result dynamic when the number of + instances changes. + ## Agent Configuration Options ```hcl