otlp: Add DeltaTemporalitySelector

Author: svix-jplatte

opentelemetry-otlp/src/lib.rs

@@ -226,7 +226,7 @@ pub use crate::span::{
 
 #[cfg(feature = "metrics")]
 pub use crate::metric::{
-    MetricsExporter, MetricsExporterBuilder, OtlpMetricPipeline,
+    DeltaTemporalitySelector, MetricsExporter, MetricsExporterBuilder, OtlpMetricPipeline,
     OTEL_EXPORTER_OTLP_METRICS_COMPRESSION, OTEL_EXPORTER_OTLP_METRICS_ENDPOINT,
     OTEL_EXPORTER_OTLP_METRICS_HEADERS, OTEL_EXPORTER_OTLP_METRICS_TIMEOUT,
 };

opentelemetry-otlp/src/metric.rs

@@ -247,6 +247,34 @@ impl<RT, EB: Debug> Debug for OtlpMetricPipeline<RT, EB> {
             .finish()
     }
 }
+/// A temporality selector that returns [`Delta`][Temporality::Delta] for all
+/// instruments except `UpDownCounter` and `ObservableUpDownCounter`.
+///
+/// This should be used over the default if you export your data to a service
+/// like DataDog that works better with delta aggregation¹.
+///
+/// ¹ as per DataDog documentation:
+/// <https://docs.datadoghq.com/opentelemetry/guide/otlp_delta_temporality/>
+#[non_exhaustive]
+pub struct DeltaTemporalitySelector;
+
+impl TemporalitySelector for DeltaTemporalitySelector {
+    fn temporality(&self, kind: InstrumentKind) -> Temporality {
+        #[rustfmt::skip]
+        match kind {
+            InstrumentKind::Counter
+            | InstrumentKind::Histogram
+            | InstrumentKind::ObservableCounter
+            | InstrumentKind::ObservableGauge => {
+                Temporality::Delta
+            }
+            InstrumentKind::UpDownCounter
+            | InstrumentKind::ObservableUpDownCounter => {
+                Temporality::Cumulative
+            }
+        }
+    }
+}
 
 /// An interface for OTLP metrics clients
 #[async_trait]