fix: allow users to use custom export kind selector.

examples/basic-otlp-with-selector/README.md

@@ -1,4 +1,7 @@
-# Basic OpenTelemetry Example
+# Basic OTLP exporter Example
 
-This example shows basic span and metric usage, and exports to the [OpenTelemetry Collector](https://github.com/open-telemetry/opentelemetry-collector) via OTLP with a custom metric aggregator selector.
+This example shows how to configure OTLP metrics exporter to use custom aggregator selectors and custom export kind selectors.
+
+## Prerequisite
+You should first start a `opentelemetry-collector` on localhost using the default configuration. 
 

examples/basic-otlp-with-selector/src/main.rs

@@ -1,6 +1,7 @@
 use futures::stream::Stream;
 use futures::StreamExt;
 use opentelemetry::global::shutdown_tracer_provider;
+use opentelemetry::sdk::export::metrics::{ExportKind, ExportKindFor};
 use opentelemetry::sdk::{
     export::metrics::{Aggregator, AggregatorSelector},
     metrics::{aggregators, PushController},
@@ -50,6 +51,15 @@ impl AggregatorSelector for CustomAggregator {
     }
 }
 
+#[derive(Debug, Clone)]
+struct CustomExportKindFor();
+
+impl ExportKindFor for CustomExportKindFor {
+    fn export_kind_for(&self, _descriptor: &Descriptor) -> ExportKind {
+        ExportKind::Delta
+    }
+}
+
 fn init_meter() -> metrics::Result<PushController> {
     let export_config = ExporterConfig {
         endpoint: "http://localhost:4317".to_string(),
@@ -58,6 +68,7 @@ fn init_meter() -> metrics::Result<PushController> {
     };
     opentelemetry_otlp::new_metrics_pipeline(tokio::spawn, delayed_interval)
         .with_export_config(export_config)
+        .with_export_kind(CustomExportKindFor())
         .with_aggregator_selector(CustomAggregator())
         .build()
 }

examples/basic-otlp/README.md

@@ -1,4 +1,6 @@
-# Basic OpenTelemetry Example
+# Basic OTLP exporter Example
 
 This example shows basic span and metric usage, and exports to the [OpenTelemetry Collector](https://github.com/open-telemetry/opentelemetry-collector) via OTLP.
 
+## Prerequisite
+You should first start a `opentelemetry-collector` on localhost using the default configuration. 

opentelemetry-otlp/src/metric.rs

@@ -169,10 +169,24 @@ where
     }
 
     /// Build with export kind selector
-    pub fn with_export_kind(self, export_selector: ES) -> Self {
+    pub fn with_export_kind<E>(
+        self,
+        export_selector: E,
+    ) -> OtlpMetricPipelineBuilder<AS, E, SP, SO, I, IO>
+    where
+        E: ExportKindFor + Send + Sync + Clone + 'static,
+    {
         OtlpMetricPipelineBuilder {
+            aggregator_selector: self.aggregator_selector,
             export_selector,
-            ..self
+            spawn: self.spawn,
+            interval: self.interval,
+            export_config: self.export_config,
+            tonic_config: self.tonic_config,
+            resource: self.resource,
+            stateful: self.stateful,
+            period: self.period,
+            timeout: self.timeout,
         }
     }