fix: Pass immutable metrics to PushMetricExporter

opentelemetry-otlp/src/exporter/http/metrics.rs

@@ -9,7 +9,7 @@
 use super::OtlpHttpClient;
 
 impl MetricsClient for OtlpHttpClient {
-    async fn export(&self, metrics: &mut ResourceMetrics) -> OTelSdkResult {
+    async fn export(&self, metrics: &ResourceMetrics) -> OTelSdkResult {
         let client = self
             .client
             .lock()

opentelemetry-otlp/src/exporter/http/mod.rs

@@ -326,11 +326,11 @@
     #[cfg(feature = "metrics")]
     fn build_metrics_export_body(
         &self,
-        metrics: &mut ResourceMetrics,
+        metrics: &ResourceMetrics,
     ) -> Option<(Vec<u8>, &'static str)> {
         use opentelemetry_proto::tonic::collector::metrics::v1::ExportMetricsServiceRequest;
 
-        let req: ExportMetricsServiceRequest = (&*metrics).into();
+        let req: ExportMetricsServiceRequest = metrics.into();
 
         match self.protocol {
             #[cfg(feature = "http-json")]

opentelemetry-otlp/src/exporter/tonic/metrics.rs

@@ -52,7 +52,7 @@
 }
 
 impl MetricsClient for TonicMetricsClient {
-    async fn export(&self, metrics: &mut ResourceMetrics) -> OTelSdkResult {
+    async fn export(&self, metrics: &ResourceMetrics) -> OTelSdkResult {
         let (mut client, metadata, extensions) = self
             .inner
             .lock()
@@ -81,7 +81,7 @@
             .export(Request::from_parts(
                 metadata,
                 extensions,
-                ExportMetricsServiceRequest::from(&*metrics),
+                ExportMetricsServiceRequest::from(metrics),
             ))
             .await
             .map_err(|e| OTelSdkError::InternalFailure(format!("{e:?}")))?;

opentelemetry-otlp/src/metric.rs

@@ -123,7 +123,7 @@
 pub(crate) trait MetricsClient: fmt::Debug + Send + Sync + 'static {
     fn export(
         &self,
-        metrics: &mut ResourceMetrics,
+        metrics: &ResourceMetrics,
     ) -> impl std::future::Future<Output = OTelSdkResult> + Send;
     fn shutdown(&self) -> OTelSdkResult;
 }
@@ -149,7 +149,7 @@
 }
 
 impl PushMetricExporter for MetricExporter {
-    async fn export(&self, metrics: &mut ResourceMetrics) -> OTelSdkResult {
+    async fn export(&self, metrics: &ResourceMetrics) -> OTelSdkResult {
         match &self.client {
             #[cfg(feature = "grpc-tonic")]
             SupportedTransportClient::Tonic(client) => client.export(metrics).await,

opentelemetry-sdk/CHANGELOG.md

@@ -43,6 +43,9 @@ also modified to suppress telemetry before invoking exporters.
 - *Breaking* `Aggregation` enum moved behind feature flag
   "spec_unstable_metrics_views". This was only required when using Views.
   [#2928](https://github.com/open-telemetry/opentelemetry-rust/pull/2928)
+- *Breaking* change, affecting custom `PushMetricExporter` authors:
+  - The `export` method on `PushMetricExporter` receives a `&ResourceMetrics`
+    instead of `&mut ResourceMetrics`.
 
 ## 0.29.0
 

opentelemetry-sdk/src/metrics/exporter.rs

@@ -18,7 +18,7 @@ pub trait PushMetricExporter: Send + Sync + 'static {
     /// considered unrecoverable and will be logged.
     fn export(
         &self,
-        metrics: &mut ResourceMetrics,
+        metrics: &ResourceMetrics,
     ) -> impl std::future::Future<Output = OTelSdkResult> + Send;
 
     /// Flushes any metric data held by an exporter.

opentelemetry-sdk/src/metrics/in_memory_exporter.rs

@@ -237,7 +237,7 @@ impl InMemoryMetricExporter {
 }
 
 impl PushMetricExporter for InMemoryMetricExporter {
-    async fn export(&self, metrics: &mut ResourceMetrics) -> OTelSdkResult {
+    async fn export(&self, metrics: &ResourceMetrics) -> OTelSdkResult {
         self.metrics
             .lock()
             .map(|mut metrics_guard| {

opentelemetry-sdk/src/metrics/periodic_reader.rs

@@ -411,7 +411,7 @@ impl<E: PushMetricExporter> PeriodicReaderInner<E> {
 
         // Relying on futures executor to execute async call.
         // TODO: Pass timeout to exporter
-        futures_executor::block_on(self.exporter.export(&mut rm))
+        futures_executor::block_on(self.exporter.export(&rm))
     }
 
     fn force_flush(&self) -> OTelSdkResult {
@@ -553,7 +553,7 @@ mod tests {
     }
 
     impl PushMetricExporter for MetricExporterThatFailsOnlyOnFirst {
-        async fn export(&self, _metrics: &mut ResourceMetrics) -> OTelSdkResult {
+        async fn export(&self, _metrics: &ResourceMetrics) -> OTelSdkResult {
             if self.count.fetch_add(1, Ordering::Relaxed) == 0 {
                 Err(OTelSdkError::InternalFailure("export failed".into()))
             } else {
@@ -584,7 +584,7 @@ mod tests {
     }
 
     impl PushMetricExporter for MockMetricExporter {
-        async fn export(&self, _metrics: &mut ResourceMetrics) -> OTelSdkResult {
+        async fn export(&self, _metrics: &ResourceMetrics) -> OTelSdkResult {
             Ok(())
         }
 

opentelemetry-sdk/src/metrics/periodic_reader_with_async_runtime.rs

@@ -259,7 +259,7 @@
             message = "Calling exporter's export method with collected metrics.",
             count = self.rm.scope_metrics.len(),
         );
-        let export = self.reader.exporter.export(&mut self.rm);
+        let export = self.reader.exporter.export(&self.rm);
         let timeout = self.runtime.delay(self.timeout);
         pin_mut!(export);
         pin_mut!(timeout);

opentelemetry-stdout/src/metrics/exporter.rs

@@ -42,7 +42,7 @@
 
 impl PushMetricExporter for MetricExporter {
     /// Write Metrics to stdout
-    async fn export(&self, metrics: &mut ResourceMetrics) -> OTelSdkResult {
+    async fn export(&self, metrics: &ResourceMetrics) -> OTelSdkResult {
         if self.is_shutdown.load(atomic::Ordering::SeqCst) {
             Err(opentelemetry_sdk::error::OTelSdkError::AlreadyShutdown)
         } else {