Add log appender for tracing (open-telemetry#1085)

Author: cijothomas

logs.rs

@@ -0,0 +1,66 @@
+use opentelemetry_api::KeyValue;
+use opentelemetry_appender_tracing::layer;
+use opentelemetry_sdk::{
+    logs::{Config, LoggerProvider},
+    Resource,
+};
+use tracing::error;
+use tracing_subscriber::{prelude::*, Layer};
+
+mod throughput;
+
+struct NoopEventVisitor;
+
+impl tracing::field::Visit for NoopEventVisitor {
+    fn record_debug(&mut self, _field: &tracing::field::Field, _value: &dyn std::fmt::Debug) {}
+}
+
+struct NoOpLogLayer;
+impl<S> Layer<S> for NoOpLogLayer
+where
+    S: tracing::Subscriber,
+{
+    fn on_event(
+        &self,
+        event: &tracing::Event<'_>,
+        _ctx: tracing_subscriber::layer::Context<'_, S>,
+    ) {
+        let mut visitor = NoopEventVisitor;
+        event.record(&mut visitor);
+    }
+
+    fn event_enabled(
+        &self,
+        _event: &tracing::Event<'_>,
+        _ctx: tracing_subscriber::layer::Context<'_, S>,
+    ) -> bool {
+        true
+    }
+}
+
+fn main() {
+    // LoggerProvider without any exporter.
+    let provider: LoggerProvider = LoggerProvider::builder()
+        .with_config(
+            Config::default().with_resource(Resource::new(vec![KeyValue::new(
+                "service.name",
+                "log-appender-tracing-example",
+            )])),
+        )
+        .build();
+
+    // Use the OpenTelemetryTracingBridge to test the throughput of the appender-tracing.
+    let layer = layer::OpenTelemetryTracingBridge::new(&provider);
+    tracing_subscriber::registry().with(layer).init();
+
+    // Use a "Do-Nothing" layer to test the throughput of the tracing system without
+    // OpenTelemetry overhead. This helps measure the OpenTelemetry overhead.
+    // let noop_layer = NoOpLogLayer;
+    // tracing_subscriber::registry().with(noop_layer).init();
+
+    throughput::test_throughput(test_log);
+}
+
+fn test_log() {
+    error!(target: "my-system", event_id = 20, event_name = "my-event_name", user_name = "otel", user_email = "otel@opentelemetry.io");
+}