Use native Rust support for async traits in LogExporter::export() method (11% improvement) (open-telemetry#2374)

Co-authored-by: Cijo Thomas <[email protected]>
Co-authored-by: Zhongyang Wu <[email protected]>

Author: 3 people

Cargo.toml

@@ -24,7 +24,6 @@ opentelemetry-stdout = { path = "../opentelemetry-stdout", features = ["logs"] }
 opentelemetry_sdk = { path = "../opentelemetry-sdk", features = ["logs", "testing"]  }
 tracing-subscriber = { workspace = true, features = ["registry", "std", "env-filter"] }
 tracing-log = "0.2"
-async-trait = { workspace = true }
 criterion = { workspace = true }
 tokio = { workspace = true, features = ["full"]}
 

benches/logs.rs

@@ -13,7 +13,6 @@
     | ot_layer_enabled            | 196 ns      |
 */
 
-use async_trait::async_trait;
 use criterion::{criterion_group, criterion_main, Criterion};
 use opentelemetry::InstrumentationScope;
 use opentelemetry_appender_tracing::layer as tracing_layer;
@@ -32,10 +31,13 @@ struct NoopExporter {
     enabled: bool,
 }
 
-#[async_trait]
 impl LogExporter for NoopExporter {
-    async fn export(&self, _: LogBatch<'_>) -> LogResult<()> {
-        LogResult::Ok(())
+    #[allow(clippy::manual_async_fn)]
+    fn export(
+        &self,
+        _batch: LogBatch<'_>,
+    ) -> impl std::future::Future<Output = LogResult<()>> + Send {
+        async { LogResult::Ok(()) }
     }
 
     fn event_enabled(&self, _: opentelemetry::logs::Severity, _: &str, _: &str) -> bool {
@@ -44,17 +46,17 @@ impl LogExporter for NoopExporter {
 }
 
 #[derive(Debug)]
-struct NoopProcessor {
-    exporter: Box<dyn LogExporter>,
+struct NoopProcessor<E: LogExporter> {
+    exporter: E,
 }
 
-impl NoopProcessor {
-    fn new(exporter: Box<dyn LogExporter>) -> Self {
+impl<E: LogExporter> NoopProcessor<E> {
+    fn new(exporter: E) -> Self {
         Self { exporter }
     }
 }
 
-impl LogProcessor for NoopProcessor {
+impl<E: LogExporter> LogProcessor for NoopProcessor<E> {
     fn emit(&self, _: &mut LogRecord, _: &InstrumentationScope) {
         // no-op
     }
@@ -124,7 +126,7 @@ fn benchmark_no_subscriber(c: &mut Criterion) {
 
 fn benchmark_with_ot_layer(c: &mut Criterion, enabled: bool, bench_name: &str) {
     let exporter = NoopExporter { enabled };
-    let processor = NoopProcessor::new(Box::new(exporter));
+    let processor = NoopProcessor::new(exporter);
     let provider = LoggerProvider::builder()
         .with_resource(
             Resource::builder_empty()

src/layer.rs

@@ -209,7 +209,6 @@ const fn severity_of_level(level: &Level) -> Severity {
 #[cfg(test)]
 mod tests {
     use crate::layer;
-    use async_trait::async_trait;
     use opentelemetry::logs::Severity;
     use opentelemetry::trace::TracerProvider as _;
     use opentelemetry::trace::{TraceContextExt, TraceFlags, Tracer};
@@ -245,13 +244,18 @@ mod tests {
     #[derive(Clone, Debug, Default)]
     struct ReentrantLogExporter;
 
-    #[async_trait]
     impl LogExporter for ReentrantLogExporter {
-        async fn export(&self, _batch: LogBatch<'_>) -> LogResult<()> {
-            // This will cause a deadlock as the export itself creates a log
-            // while still within the lock of the SimpleLogProcessor.
-            warn!(name: "my-event-name", target: "reentrant", event_id = 20, user_name = "otel", user_email = "[email protected]");
-            Ok(())
+        #[allow(clippy::manual_async_fn)]
+        fn export(
+            &self,
+            _batch: LogBatch<'_>,
+        ) -> impl std::future::Future<Output = LogResult<()>> + Send {
+            async {
+                // This will cause a deadlock as the export itself creates a log
+                // while still within the lock of the SimpleLogProcessor.
+                warn!(name: "my-event-name", target: "reentrant", event_id = 20, user_name = "otel", user_email = "[email protected]");
+                Ok(())
+            }
         }
     }