Fix first run of linear regression erroring out (#54)

CHANGELOG.md

@@ -5,6 +5,11 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Changed
+- Updated to Custom Pod Autoscaler `v2.2.0`.
+- Updated to Horizontal Pod Autoscaler CPA `v0.7.0`.
+### Fixed
+- Linear regression no longer fails on first run.
 
 ## [v0.7.0] - 2021-04-05
 ### Added

internal/prediction/linear/linear.go

@@ -58,6 +58,16 @@ func (p *Predict) GetPrediction(model *config.Model, evaluations []*stored.Evalu
 		return 0, errors.New("No Linear configuration provided for model")
 	}
 
+	if len(evaluations) == 0 {
+		return 0, errors.New("No evaluations provided for Linear regression model")
+	}
+
+	if len(evaluations) == 1 {
+		// If only 1 evaluation is provided do not try and calculate using the linear regression model, just return
+		// the target replicas from the only evaluation
+		return evaluations[0].Evaluation.TargetReplicas, nil
+	}
+
 	parameters, err := json.Marshal(linearRegressionParameters{
 		LookAhead:   model.Linear.LookAhead,
 		Evaluations: evaluations,

internal/prediction/linear/linear_test.go

@@ -52,6 +52,41 @@ func TestPredict_GetPrediction(t *testing.T) {
 			&config.Model{},
 			[]*stored.Evaluation{},
 		},
+		{
+			"Fail no evaluations",
+			0,
+			errors.New("No evaluations provided for Linear regression model"),
+			&linear.Predict{},
+			&config.Model{
+				Type: linear.Type,
+				Linear: &config.Linear{
+					StoredValues: 5,
+					LookAhead:    0,
+				},
+			},
+			[]*stored.Evaluation{},
+		},
+		{
+			"Success, only one evaluation, return without the prediction",
+			32,
+			nil,
+			&linear.Predict{},
+			&config.Model{
+				Type: linear.Type,
+				Linear: &config.Linear{
+					StoredValues: 5,
+					LookAhead:    0,
+				},
+			},
+			[]*stored.Evaluation{
+				{
+					ID: 0,
+					Evaluation: stored.DBEvaluation{
+						TargetReplicas: 32,
+					},
+				},
+			},
+		},
 		{
 			"Fail execution of algorithm fails",
 			0,
@@ -70,7 +105,14 @@ func TestPredict_GetPrediction(t *testing.T) {
 					LookAhead:    0,
 				},
 			},
-			[]*stored.Evaluation{},
+			[]*stored.Evaluation{
+				{
+					ID: 0,
+				},
+				{
+					ID: 1,
+				},
+			},
 		},
 		{
 			"Fail algorithm returns non-integer castable value",
@@ -90,7 +132,14 @@ func TestPredict_GetPrediction(t *testing.T) {
 					LookAhead:    0,
 				},
 			},
-			[]*stored.Evaluation{},
+			[]*stored.Evaluation{
+				{
+					ID: 0,
+				},
+				{
+					ID: 1,
+				},
+			},
 		},
 		{
 			"Success",
@@ -110,7 +159,14 @@ func TestPredict_GetPrediction(t *testing.T) {
 					LookAhead:    0,
 				},
 			},
-			[]*stored.Evaluation{},
+			[]*stored.Evaluation{
+				{
+					ID: 0,
+				},
+				{
+					ID: 1,
+				},
+			},
 		},
 	}
 	for _, test := range tests {