Add OTLPMetricPipeline builder methods for delta and lowmemory

opentelemetry-otlp/CHANGELOG.md

@@ -1,4 +1,11 @@
 # Changelog
+
+## Unreleased
+
+### Added
+- Added builder methods to configure delta, low-memory temporality for OTLP
+  Metric pipeline
+
 ## v0.12.0
 
 ### Added

opentelemetry-otlp/src/metric.rs

@@ -100,6 +100,56 @@ impl From<TonicExporterBuilder> for MetricsExporterBuilder {
     }
 }
 
+/// Configure delta temporality for all [InstrumentKind]
+///
+/// [Temporality::Delta] will be used for Counter, Asynchronous Counter and Histogram
+/// [Temporality::Cumulative] will be used for UpDownCounter and Asynchronous UpDownCounter
+#[derive(Clone, Default, Debug)]
+struct DeltaTemporalitySelector {
+    pub(crate) _private: (),
+}
+
+impl DeltaTemporalitySelector {
+    /// Create a new default temporality selector.
+    fn new() -> Self {
+        Self::default()
+    }
+}
+
+impl TemporalitySelector for DeltaTemporalitySelector {
+    fn temporality(&self, _kind: InstrumentKind) -> Temporality {
+        Temporality::Delta
+    }
+}
+
+/// Configure low memory temporality for all [InstrumentKind]
+///
+/// [Temporality::Delta] will be used for Counter and Histogram
+/// [Temporality::Cumulative] will be used for UpDownCounter, Asynchronous Counter and Asynchronous UpDownCounter
+#[derive(Clone, Default, Debug)]
+struct LowMemoryTemporalitySelector {
+    pub(crate) _private: (),
+}
+
+impl LowMemoryTemporalitySelector {
+    /// Create a new default temporality selector.
+    fn new() -> Self {
+        Self::default()
+    }
+}
+
+impl TemporalitySelector for LowMemoryTemporalitySelector {
+    fn temporality(&self, kind: InstrumentKind) -> Temporality {
+        match kind {
+            InstrumentKind::Counter | InstrumentKind::Histogram => Temporality::Delta,
+            InstrumentKind::UpDownCounter
+            | InstrumentKind::ObservableCounter
+            | InstrumentKind::ObservableGauge
+            | InstrumentKind::ObservableUpDownCounter => Temporality::Cumulative,
+        }
+    }
+}
+
 /// Pipeline to build OTLP metrics exporter
 ///
 /// Note that currently the OTLP metrics exporter only supports tonic as it's grpc layer and tokio as
@@ -158,6 +208,28 @@ where
         }
     }
 
+    /// Build with Delta temporality
+    /// This choses Delta for Counter, Asynchronous Counter and Histogram,
+    /// and choses Cumulative for UpDownCounter and Asynchronous UpDownCounter
+    pub fn with_delta_temporality(self) -> Self {
+        // This implements Delta from : https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/sdk_exporters/otlp.md#additional-configuration
+        OtlpMetricPipeline {
+            temporality_selector: Some(Box::new(DeltaTemporalitySelector::new())),
+            ..self
+        }
+    }
+
+    /// Build with "LowMemory" temporality
+    /// This choses Delta for Synchronous Counter and Histogram,
+    /// and choses Cumulative for UpDownCounter, Asynchronous Counter and Asynchronous UpDownCounter
+    pub fn with_low_memory_temporality(self) -> Self {
+        // This implements LowMemory from : https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/sdk_exporters/otlp.md#additional-configuration
+        OtlpMetricPipeline {
+            temporality_selector: Some(Box::new(DeltaTemporalitySelector::new())),
+            ..self
+        }
+    }
+
     /// Build with the given aggregation selector
     pub fn with_aggregation_selector<T: AggregationSelector + 'static>(self, selector: T) -> Self {
         OtlpMetricPipeline {