Remove mut self reference from SpanExporter::export() method. (#2695)

Author: lalitb

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

@@ -9,7 +9,7 @@ use opentelemetry_sdk::{
 };
 
 impl SpanExporter for OtlpHttpClient {
-    async fn export(&mut self, batch: Vec<SpanData>) -> OTelSdkResult {
+    async fn export(&self, batch: Vec<SpanData>) -> OTelSdkResult {
         let client = match self
             .client
             .lock()

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

@@ -1,4 +1,5 @@
 use core::fmt;
+use tokio::sync::Mutex;
 
 use opentelemetry::otel_debug;
 use opentelemetry_proto::tonic::collector::trace::v1::{
@@ -23,7 +24,7 @@ pub(crate) struct TonicTracesClient {
 
 struct ClientInner {
     client: TraceServiceClient<Channel>,
-    interceptor: BoxInterceptor,
+    interceptor: Mutex<BoxInterceptor>,
 }
 
 impl fmt::Debug for TonicTracesClient {
@@ -50,26 +51,27 @@ impl TonicTracesClient {
         TonicTracesClient {
             inner: Some(ClientInner {
                 client,
-                interceptor,
+                interceptor: Mutex::new(interceptor),
             }),
             resource: Default::default(),
         }
     }
 }
 
 impl SpanExporter for TonicTracesClient {
-    async fn export(&mut self, batch: Vec<SpanData>) -> OTelSdkResult {
-        let (mut client, metadata, extensions) = match &mut self.inner {
+    async fn export(&self, batch: Vec<SpanData>) -> OTelSdkResult {
+        let (mut client, metadata, extensions) = match &self.inner {
             Some(inner) => {
-                let (m, e, _) = match inner.interceptor.call(Request::new(())) {
-                    Ok(res) => res.into_parts(),
-                    Err(e) => return Err(OTelSdkError::InternalFailure(e.to_string())),
-                };
+                let (m, e, _) = inner
+                    .interceptor
+                    .lock()
+                    .await // tokio::sync::Mutex doesn't return a poisoned error, so we can safely use the interceptor here
+                    .call(Request::new(()))
+                    .map_err(|e| OTelSdkError::InternalFailure(format!("error: {:?}", e)))?
+                    .into_parts();
                 (inner.client.clone(), m, e)
             }
-            None => {
-                return Err(OTelSdkError::AlreadyShutdown);
-            }
+            None => return Err(OTelSdkError::AlreadyShutdown),
         };
 
         let resource_spans = group_spans_by_resource_and_scope(batch, &self.resource);

opentelemetry-otlp/src/span.rs

@@ -141,8 +141,8 @@ impl SpanExporter {
 }
 
 impl opentelemetry_sdk::trace::SpanExporter for SpanExporter {
-    async fn export(&mut self, batch: Vec<SpanData>) -> OTelSdkResult {
-        match &mut self.client {
+    async fn export(&self, batch: Vec<SpanData>) -> OTelSdkResult {
+        match &self.client {
             #[cfg(feature = "grpc-tonic")]
             SupportedTransportClient::Tonic(client) => client.export(batch).await,
             #[cfg(any(feature = "http-proto", feature = "http-json"))]

opentelemetry-sdk/CHANGELOG.md

@@ -33,7 +33,17 @@
     }
 }
 ```
-
+- **Breaking** The SpanExporter::export() method no longer requires a mutable reference to self.
+  Before: 
+  ```rust
+    async fn export(&mut self, batch: Vec<SpanData>) -> OTelSdkResult 
+  ```
+  After: 
+  ```rust 
+    async fn export(&self, batch: Vec<SpanData>) -> OTelSdkResult  
+  ```
+  Custom exporters will need to internally synchronize any mutable state, if applicable.
+  
 ## 0.28.0
 
 Released 2025-Feb-10

opentelemetry-sdk/benches/context.rs

@@ -136,7 +136,7 @@ fn parent_sampled_tracer(inner_sampler: Sampler) -> (SdkTracerProvider, BoxedTra
 struct NoopExporter;
 
 impl SpanExporter for NoopExporter {
-    async fn export(&mut self, _spans: Vec<SpanData>) -> OTelSdkResult {
+    async fn export(&self, _spans: Vec<SpanData>) -> OTelSdkResult {
         Ok(())
     }
 }

opentelemetry-sdk/benches/span_builder.rs

@@ -65,7 +65,7 @@ fn not_sampled_provider() -> (sdktrace::SdkTracerProvider, sdktrace::SdkTracer)
 struct NoopExporter;
 
 impl SpanExporter for NoopExporter {
-    async fn export(&mut self, _spans: Vec<SpanData>) -> OTelSdkResult {
+    async fn export(&self, _spans: Vec<SpanData>) -> OTelSdkResult {
         Ok(())
     }
 }

opentelemetry-sdk/benches/trace.rs

@@ -59,7 +59,7 @@ fn criterion_benchmark(c: &mut Criterion) {
 struct VoidExporter;
 
 impl SpanExporter for VoidExporter {
-    async fn export(&mut self, _spans: Vec<SpanData>) -> OTelSdkResult {
+    async fn export(&self, _spans: Vec<SpanData>) -> OTelSdkResult {
         Ok(())
     }
 }

opentelemetry-sdk/src/testing/trace/span_exporters.rs

@@ -41,7 +41,7 @@ pub struct TokioSpanExporter {
 }
 
 impl SpanExporter for TokioSpanExporter {
-    async fn export(&mut self, batch: Vec<SpanData>) -> OTelSdkResult {
+    async fn export(&self, batch: Vec<SpanData>) -> OTelSdkResult {
         batch.into_iter().try_for_each(|span_data| {
             self.tx_export
                 .send(span_data)
@@ -110,7 +110,7 @@ impl NoopSpanExporter {
 }
 
 impl SpanExporter for NoopSpanExporter {
-    async fn export(&mut self, _: Vec<SpanData>) -> OTelSdkResult {
+    async fn export(&self, _: Vec<SpanData>) -> OTelSdkResult {
         Ok(())
     }
 }

opentelemetry-sdk/src/trace/export.rs

@@ -28,7 +28,7 @@ pub trait SpanExporter: Send + Sync + Debug {
     /// Any retry logic that is required by the exporter is the responsibility
     /// of the exporter.
     fn export(
-        &mut self,
+        &self,
         batch: Vec<SpanData>,
     ) -> impl std::future::Future<Output = OTelSdkResult> + Send;
 

opentelemetry-sdk/src/trace/in_memory_exporter.rs

@@ -130,7 +130,7 @@ impl InMemorySpanExporter {
 }
 
 impl SpanExporter for InMemorySpanExporter {
-    async fn export(&mut self, batch: Vec<SpanData>) -> OTelSdkResult {
+    async fn export(&self, batch: Vec<SpanData>) -> OTelSdkResult {
         let result = self
             .spans
             .lock()