Small change to return error from periodic exporter (#1857)

Co-authored-by: Cijo Thomas <cijo.thomas@gmail.com>

Author: lalitb

opentelemetry-sdk/CHANGELOG.md

@@ -45,6 +45,8 @@
 
 - **Breaking** [1850] (https://github.com/open-telemetry/opentelemetry-rust/pull/1850) `LoggerProvider::log_processors()` and `LoggerProvider::resource()` are not public methods anymore. They are only used within the `opentelemetry-sdk` crate.
 
+- [1857](https://github.com/open-telemetry/opentelemetry-rust/pull/1857) Fixed an issue in Metrics SDK which prevented export errors from being send to global error handler. With the fix, errors occurring during export like OTLP Endpoint unresponsive shows up in stderr by default.
+
 ## v0.23.0
 
 - Fix SimpleSpanProcessor to be consistent with log counterpart. Also removed

opentelemetry-sdk/src/metrics/periodic_reader.rs

@@ -260,7 +260,7 @@ impl<RT: Runtime> PeriodicReaderWorker<RT> {
         pin_mut!(timeout);
 
         match future::select(export, timeout).await {
-            Either::Left(_) => Ok(()),
+            Either::Left((res, _)) => res, // return the result.
             Either::Right(_) => Err(MetricsError::Other("export timed out".into())),
         }
     }