Remove old global meter provider shutdown method (#1412)

This change removes the old `global::shutdown_meter_provider` method
which is not part of the metrics API spec, and properly documents the
`SdkMeterProvider::shutdown` method which is spec compliant.

opentelemetry-sdk/src/metrics/meter_provider.rs

@@ -58,30 +58,31 @@ impl SdkMeterProvider {
     /// use opentelemetry_sdk::metrics::SdkMeterProvider;
     ///
     /// fn init_metrics() -> SdkMeterProvider {
+    ///     // Setup metric pipelines with readers + views, default has no
+    ///     // readers so nothing is exported.
     ///     let provider = SdkMeterProvider::default();
     ///
     ///     // Set provider to be used as global meter provider
     ///     let _ = global::set_meter_provider(provider.clone());
     ///
-    ///     // Setup metric pipelines with readers + views
-    ///
     ///     provider
     /// }
     ///
-    /// fn main() {
+    /// fn main() -> Result<(), Box<dyn std::error::Error>> {
     ///     let provider = init_metrics();
     ///
     ///     // create instruments + record measurements
     ///
     ///     // force all instruments to flush
-    ///     provider.force_flush().unwrap();
+    ///     provider.force_flush()?;
     ///
     ///     // record more measurements..
     ///
-    ///     // dropping provider and shutting down global provider ensure all
-    ///     // remaining metrics data are exported
-    ///     drop(provider);
-    ///     global::shutdown_meter_provider();
+    ///     // shutdown ensures any cleanup required by the provider is done,
+    ///     // and also invokes shutdown on the readers.
+    ///     provider.shutdown()?;
+    ///
+    ///     Ok(())
     /// }
     /// ```
     pub fn force_flush(&self) -> Result<()> {

opentelemetry/CHANGELOG.md

@@ -10,7 +10,6 @@ of entries, so moving from `IndexMap` to `HashMap` offers slight performance
 gains, and avoids `IndexMap` dependency. This affects `body` and `attributes` of
 `LogRecord`.
 [#1353](https://github.com/open-telemetry/opentelemetry-rust/pull/1353)
-
 - Add `TextMapCompositePropagator` [#1373](https://github.com/open-telemetry/opentelemetry-rust/pull/1373)
 
 ### Removed
@@ -19,6 +18,8 @@ gains, and avoids `IndexMap` dependency. This affects `body` and `attributes` of
 `HashMap`.
 [#1353](https://github.com/open-telemetry/opentelemetry-rust/pull/1353)
 - Remove API for Creating Histograms with signed integers. [#1371](https://github.com/open-telemetry/opentelemetry-rust/pull/1371)
+- Remove `global::shutdown_meter_provider`, use `SdkMeterProvider::shutdown`
+  directly instead (#1412).
 
 ## [v0.21.0](https://github.com/open-telemetry/opentelemetry-rust/compare/v0.20.0...v0.21.0)
 

opentelemetry/src/global/metrics.rs

@@ -98,14 +98,6 @@ where
     *global_provider = GlobalMeterProvider::new(new_provider);
 }
 
-/// Shut down the current meter global meter provider.
-pub fn shutdown_meter_provider() {
-    let mut global_provider = GLOBAL_METER_PROVIDER
-        .write()
-        .expect("GLOBAL_METER_PROVIDER RwLock poisoned");
-    *global_provider = GlobalMeterProvider::new(metrics::noop::NoopMeterProvider::new());
-}
-
 /// Returns an instance of the currently configured global [`MeterProvider`]
 /// through [`GlobalMeterProvider`].
 pub fn meter_provider() -> GlobalMeterProvider {