Handle no metrics found for AWS Cloudwatch (#2345)

Signed-off-by: Althaf Mohamed <amohamed@duosecurity.com>

CHANGELOG.md

@@ -34,6 +34,7 @@
 
 - Artemis Scaler: parse out broker config parameters in case `restAPITemplate` is given ([#2104](https://github.com/kedacore/keda/pull/2104))
 - AWS Cloudwatch Scaler: improve metric exporting logic ([#2243](https://github.com/kedacore/keda/pull/2243))
+- AWS Cloudwatch Scaler: return minimum value for the metric when cloudwatch returns empty list ([#2345](https://github.com/kedacore/keda/pull/2345))
 - Azure Log Analytics Scaler: add support to provide the metric name([#2106](https://github.com/kedacore/keda/pull/2106))
 - Azure Pipelines Scaler: improve logs ([#2297](https://github.com/kedacore/keda/pull/2297))
 - Cron Scaler: improve validation in case start & end input is same ([#2032](https://github.com/kedacore/keda/pull/2032))

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())
 		}