[exporter/awsemfexporter] Add config option to retain the initial val…

…ue of delta metrics (#16218)

.chloggen/awsemfexporter_retein_intitial_delta_value.yaml

@@ -0,0 +1,16 @@
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: awsemfexporter
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: The AWS EMF exporter now supports the additional configuration flag `retain_initial_value_of_delta_metric`. With this flag active the first value of a metric is not discarded but instead sent to AWS.
+
+# One or more tracking issues related to the change
+issues: [16218]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:

exporter/awsemfexporter/config.go

@@ -43,6 +43,11 @@ type Config struct {
 	// Namespace is a container for CloudWatch metrics.
 	// Metrics in different namespaces are isolated from each other.
 	Namespace string `mapstructure:"namespace"`
+	// RetainInitialValueOfDeltaMetric is the flag to signal that the initial value of a metric is a valid datapoint.
+	// The default behavior is that the first value occurrence of a metric is set as the baseline for the calculation of
+	// the delta to the next occurrence. With this flag set to true the exporter will instead use this first value as the
+	// initial delta value. This is especially useful when handling low frequency metrics.
+	RetainInitialValueOfDeltaMetric bool `mapstructure:"retain_initial_value_of_delta_metric"`
 	// DimensionRollupOption is the option for metrics dimension rollup. Three options are available, default option is "ZeroAndSingleDimensionRollup".
 	// "ZeroAndSingleDimensionRollup" - Enable both zero dimension rollup and single dimension rollup
 	// "SingleDimensionRollupOnly" - Enable single dimension rollup

exporter/awsemfexporter/datapoint.go

@@ -63,11 +63,12 @@ type dataPoints interface {
 
 // deltaMetricMetadata contains the metadata required to perform rate/delta calculation
 type deltaMetricMetadata struct {
-	adjustToDelta bool
-	metricName    string
-	namespace     string
-	logGroup      string
-	logStream     string
+	adjustToDelta              bool
+	retainInitialValueForDelta bool
+	metricName                 string
+	namespace                  string
+	logGroup                   string
+	logStream                  string
 }
 
 // numberDataPointSlice is a wrapper for pmetric.NumberDataPointSlice
@@ -114,6 +115,13 @@ func (dps numberDataPointSlice) At(i int) (dataPoint, bool) {
 		var deltaVal interface{}
 		mKey := aws.NewKey(dps.deltaMetricMetadata, labels)
 		deltaVal, retained = deltaMetricCalculator.Calculate(mKey, metricVal, metric.Timestamp().AsTime())
+
+		// If a delta to the previous data point could not be computed use the current metric value instead
+		if !retained && dps.retainInitialValueForDelta {
+			retained = true
+			deltaVal = metricVal
+		}
+
 		if !retained {
 			return dataPoint{}, retained
 		}
@@ -163,6 +171,13 @@ func (dps summaryDataPointSlice) At(i int) (dataPoint, bool) {
 		mKey := aws.NewKey(dps.deltaMetricMetadata, labels)
 
 		delta, retained = summaryMetricCalculator.Calculate(mKey, summaryMetricEntry{sum, count}, metric.Timestamp().AsTime())
+
+		// If a delta to the previous data point could not be computed use the current metric value instead
+		if !retained && dps.retainInitialValueForDelta {
+			retained = true
+			delta = summaryMetricEntry{sum, count}
+		}
+
 		if !retained {
 			return dataPoint{}, retained
 		}
@@ -208,6 +223,7 @@ func createLabels(attributes pcommon.Map, instrLibName string) map[string]string
 func getDataPoints(pmd pmetric.Metric, metadata cWMetricMetadata, logger *zap.Logger) (dps dataPoints) {
 	adjusterMetadata := deltaMetricMetadata{
 		false,
+		metadata.retainInitialValueForDelta,
 		pmd.Name(),
 		metadata.namespace,
 		metadata.logGroup,