Handle no metrics found for AWS Cloudwatch

CHANGELOG.md

@@ -29,6 +29,7 @@
 - ScaledJob: introduce `RolloutStrategy` ([#2164](https://github.com/kedacore/keda/pull/2164))
 - Add ScalersCache to reuse scalers unless they need changing ([#2187](https://github.com/kedacore/keda/pull/2187))
 - Cache metric names provided by KEDA Metrics Server ([#2279](https://github.com/kedacore/keda/pull/2279))
+- Return minimum value for the metric and log, when cloudwatch returns empty list of metrics ([#2345](https://github.com/kedacore/keda/pull/2345))
 
 ### Improvements
 

pkg/scalers/aws_cloudwatch_scaler.go

@@ -367,7 +367,8 @@ func (c *awsCloudwatchScaler) GetCloudwatchMetrics() (float64, error) {
 	if len(output.MetricDataResults) > 0 && len(output.MetricDataResults[0].Values) > 0 {
 		metricValue = *output.MetricDataResults[0].Values[0]
 	} else {
-		return -1, fmt.Errorf("metric data not received")
+		cloudwatchLog.Info("empty metric data received, returning minMetricValue")
+		metricValue = c.metadata.minMetricValue
 	}
 
 	return metricValue, nil

pkg/scalers/aws_cloudwatch_test.go

@@ -360,7 +360,23 @@ var awsCloudwatchGetMetricTestData = []awsCloudwatchMetadata{
 	},
 	{
 		namespace:            "Custom",
-		metricsName:          "Error",
+		metricsName:          testAWSCloudwatchErrorMetric,
+		dimensionName:        []string{"DIM"},
+		dimensionValue:       []string{"DIM_VALUE"},
+		targetMetricValue:    100,
+		minMetricValue:       0,
+		metricCollectionTime: 60,
+		metricStat:           "Average",
+		metricUnit:           "",
+		metricStatPeriod:     60,
+		metricEndTimeOffset:  60,
+		awsRegion:            "us-west-2",
+		awsAuthorization:     awsAuthorizationMetadata{podIdentityOwner: false},
+		scalerIndex:          0,
+	},
+	{
+		namespace:            "Custom",
+		metricsName:          testAWSCloudwatchNoValueMetric,
 		dimensionName:        []string{"DIM"},
 		dimensionValue:       []string{"DIM_VALUE"},
 		targetMetricValue:    100,
@@ -436,7 +452,7 @@ func TestAWSCloudwatchScalerGetMetrics(t *testing.T) {
 		case testAWSCloudwatchErrorMetric:
 			assert.Error(t, err, "expect error because of cloudwatch api error")
 		case testAWSCloudwatchNoValueMetric:
-			assert.Error(t, err, "expect error because of no data return from cloudwatch")
+			assert.NoError(t,err, "dont expect error when returning empty metric list from cloudwatch")
 		default:
 			assert.EqualValues(t, int64(10.0), value[0].Value.Value())
 		}