Provide default implementation for MetricExporter trait methods

Author: cijothomas

opentelemetry-otlp/src/metric.rs

@@ -144,11 +144,6 @@ impl PushMetricExporter for MetricExporter {
         self.client.export(metrics).await
     }
 
-    async fn force_flush(&self) -> MetricResult<()> {
-        // this component is stateless
-        Ok(())
-    }
-
     fn shutdown(&self) -> MetricResult<()> {
         self.client.shutdown()
     }

opentelemetry-sdk/CHANGELOG.md

@@ -211,6 +211,15 @@ metadata, a feature introduced in version 0.1.40. [#2418](https://github.com/ope
     - Continue enabling one of the async runtime feature flags: `rt-tokio`,
       `rt-tokio-current-thread`, or `rt-async-std`.
 
+`PushMetricExporter` now provides default implementation for the following methods.
+Custom exporter authors may rely on the defaults, if applicable. 
+  * `force_flush()`
+default implementation returns Ok(()) Result. 
+  * `shutdown()` default
+implementation returns Ok(()) Result. 
+  * `temporality()` default implementation
+returns `Temporality::Cumulative`.
+
 ## 0.27.1
 
 Released 2024-Nov-27

opentelemetry-sdk/src/metrics/exporter.rs

@@ -21,14 +21,23 @@ pub trait PushMetricExporter: Send + Sync + 'static {
     async fn export(&self, metrics: &mut ResourceMetrics) -> MetricResult<()>;
 
     /// Flushes any metric data held by an exporter.
-    async fn force_flush(&self) -> MetricResult<()>;
+    async fn force_flush(&self) -> MetricResult<()>
+    {
+        Ok(())
+    }
 
     /// Releases any held computational resources.
     ///
     /// After Shutdown is called, calls to Export will perform no operation and
     /// instead will return an error indicating the shutdown state.
-    fn shutdown(&self) -> MetricResult<()>;
+    fn shutdown(&self) -> MetricResult<()>
+    {
+        Ok(())
+    }
 
     /// Access the [Temporality] of the MetricExporter.
-    fn temporality(&self) -> Temporality;
+    fn temporality(&self) -> Temporality
+    {
+        Temporality::Cumulative
+    }
 }

opentelemetry-sdk/src/metrics/periodic_reader.rs

@@ -518,18 +518,6 @@ mod tests {
                 Ok(())
             }
         }
-
-        async fn force_flush(&self) -> MetricResult<()> {
-            Ok(())
-        }
-
-        fn shutdown(&self) -> MetricResult<()> {
-            Ok(())
-        }
-
-        fn temporality(&self) -> Temporality {
-            Temporality::Cumulative
-        }
     }
 
     #[derive(Debug, Clone, Default)]
@@ -543,18 +531,10 @@ mod tests {
             Ok(())
         }
 
-        async fn force_flush(&self) -> MetricResult<()> {
-            Ok(())
-        }
-
         fn shutdown(&self) -> MetricResult<()> {
             self.is_shutdown.store(true, Ordering::Relaxed);
             Ok(())
         }
-
-        fn temporality(&self) -> Temporality {
-            Temporality::Cumulative
-        }
     }
 
     #[test]

opentelemetry-sdk/src/testing/metrics/in_memory_exporter.rs

@@ -273,14 +273,6 @@ impl PushMetricExporter for InMemoryMetricExporter {
             .map_err(MetricError::from)
     }
 
-    async fn force_flush(&self) -> MetricResult<()> {
-        Ok(()) // In this implementation, flush does nothing
-    }
-
-    fn shutdown(&self) -> MetricResult<()> {
-        Ok(())
-    }
-
     fn temporality(&self) -> Temporality {
         self.temporality
     }

opentelemetry-stdout/src/metrics/exporter.rs

@@ -54,11 +54,6 @@ impl PushMetricExporter for MetricExporter {
         }
     }
 
-    async fn force_flush(&self) -> MetricResult<()> {
-        // exporter holds no state, nothing to flush
-        Ok(())
-    }
-
     fn shutdown(&self) -> MetricResult<()> {
         self.is_shutdown.store(true, atomic::Ordering::SeqCst);
         Ok(())