[Metrics builder] Add ability to override start time per resource

cmd/mdatagen/metrics_v2.tmpl

@@ -185,37 +185,58 @@ func (mb *MetricsBuilder) updateCapacity(rm pmetric.ResourceMetrics) {
 	}
 }
 
-// ResourceOption applies changes to provided resource.
-type ResourceOption func(pcommon.Resource)
+// ResourceMetricsOption applies changes to provided resource metrics.
+type ResourceMetricsOption func(pmetric.ResourceMetrics)
 
 {{- range $name, $attr := .ResourceAttributes }}
 // With{{ $name.Render }} sets provided value as "{{ $name }}" attribute for current resource.
-func With{{ $name.Render }}(val {{ $attr.Type.Primitive }}) ResourceOption {
-	return func(r pcommon.Resource) {
-		r.Attributes().Upsert{{ $attr.Type }}("{{ $name }}", val)
+func With{{ $name.Render }}(val {{ $attr.Type.Primitive }}) ResourceMetricsOption {
+	return func(rm pmetric.ResourceMetrics) {
+		rm.Resource().Attributes().Upsert{{ $attr.Type }}("{{ $name }}", val)
 	}
 }
 {{ end }}
 
+// WithStartTimeOverride overrides start time for all the resource metrics data points.
+// This option should be only used if different start time has to be set on metrics coming from different resources.
+func WithStartTimeOverride(start pcommon.Timestamp) ResourceMetricsOption {
+	return func(rm pmetric.ResourceMetrics) {
+		metrics := rm.ScopeMetrics().At(0).Metrics()
+		for i := 0; i < metrics.Len(); i++ {
+			dps := pmetric.NewNumberDataPointSlice()
+			switch metrics.At(i).DataType() {
+			case pmetric.MetricDataTypeGauge:
+				dps = metrics.At(i).Gauge().DataPoints()
+			case pmetric.MetricDataTypeSum:
+				dps = metrics.At(i).Sum().DataPoints()
+			}
+			for j := 0; j < dps.Len(); j++ {
+				dps.At(j).SetStartTimestamp(start)
+			}
+		}
+	}
+}
+
 // EmitForResource saves all the generated metrics under a new resource and updates the internal state to be ready for
 // recording another set of data points as part of another resource. This function can be helpful when one scraper
 // needs to emit metrics from several resources. Otherwise calling this function is not required,
-// just `Emit` function can be called instead. Resource attributes should be provided as ResourceOption arguments.
-func (mb *MetricsBuilder) EmitForResource(ro ...ResourceOption) {
+// just `Emit` function can be called instead.
+// Resource attributes should be provided as ResourceMetricsOption arguments.
+func (mb *MetricsBuilder) EmitForResource(rmo ...ResourceMetricsOption) {
 	rm := pmetric.NewResourceMetrics()
 	{{- if .SemConvVersion }}
 	rm.SetSchemaUrl(conventions.SchemaURL)
 	{{- end }}
 	rm.Resource().Attributes().EnsureCapacity(mb.resourceCapacity)
-	for _, op := range ro {
-		op(rm.Resource())
-	}
 	ils := rm.ScopeMetrics().AppendEmpty()
 	ils.Scope().SetName("otelcol/{{ .Name }}")
 	ils.Metrics().EnsureCapacity(mb.metricsCapacity)
 	{{- range $name, $metric := .Metrics }}
 	mb.metric{{- $name.Render }}.emit(ils.Metrics())
 	{{- end }}
+	for _, op := range rmo {
+		op(rm)
+	}
 	if ils.Metrics().Len() > 0 {
 		mb.updateCapacity(rm)
 		rm.MoveTo(mb.metricsBuffer.ResourceMetrics().AppendEmpty())
@@ -225,8 +246,8 @@ func (mb *MetricsBuilder) EmitForResource(ro ...ResourceOption) {
 // Emit returns all the metrics accumulated by the metrics builder and updates the internal state to be ready for
 // recording another set of metrics. This function will be responsible for applying all the transformations required to
 // produce metric representation defined in metadata and user settings, e.g. delta or cumulative.
-func (mb *MetricsBuilder) Emit(ro ...ResourceOption) pmetric.Metrics {
-	mb.EmitForResource(ro...)
+func (mb *MetricsBuilder) Emit(rmo ...ResourceMetricsOption) pmetric.Metrics {
+	mb.EmitForResource(rmo...)
 	metrics := pmetric.NewMetrics()
 	mb.metricsBuffer.MoveTo(metrics)
 	return metrics