Fix threhold plugin logic when there are not enough metrics within bo…

…unds (#537)

CHANGELOG.md

@@ -7,6 +7,7 @@ IMPROVEMENTS:
 
 BUG FIXES:
  * scaleutils: Fixed `least_busy` node selector on clusters running servers older than v1.0.0 [[GH-508](https://github.com/hashicorp/nomad-autoscaler/pull/508)]
+ * plugins/strategy/threshold: Fixed an issue where the wrong scaling action was taken even when the threshold was no met [[GH-537](https://github.com/hashicorp/nomad-autoscaler/pull/537)]
 
 ## 0.3.3 (May 03, 2021)
 

plugins/builtin/strategy/threshold/plugin/plugin.go

@@ -102,7 +102,8 @@ func (s *StrategyPlugin) Run(eval *sdk.ScalingCheckEvaluation, count int64) (*sd
 	// Check if we have enough data points within bounds.
 	if !withinBounds(logger, eval.Metrics, config) {
 		logger.Trace("not enough data points within bounds")
-		return nil, nil
+		eval.Action.Direction = sdk.ScaleDirectionNone
+		return eval, nil
 	}
 
 	// Calculate new count.

plugins/builtin/strategy/threshold/plugin/plugin_test.go

@@ -143,7 +143,9 @@ func TestThresholdPlugin(t *testing.T) {
 				"upper_bound": "20",
 				"delta":       "1",
 			},
-			expectedAction: nil,
+			expectedAction: &sdk.ScalingAction{
+				Direction: sdk.ScaleDirectionNone,
+			},
 		},
 		{
 			name:    "custom trigger value",