feat(router_env): add sampling_rate for traces (#335)

crates/router_env/src/logger/config.rs

@@ -90,6 +90,8 @@ pub struct LogConsole {
 pub struct LogTelemetry {
     /// Whether tracing/telemetry is enabled.
     pub enabled: bool,
+    /// Sampling rate for traces
+    pub sampling_rate: Option<f64>,
 }
 
 /// Telemetry / tracing.

crates/router_env/src/logger/setup.rs

@@ -42,6 +42,9 @@ pub fn setup<Str: AsRef<str>>(
 
     let telemetry = if conf.telemetry.enabled {
         let trace_config = trace::config()
+            .with_sampler(trace::Sampler::TraceIdRatioBased(
+                conf.telemetry.sampling_rate.unwrap_or(1.0),
+            ))
             .with_resource(Resource::new(vec![KeyValue::new("service.name", "router")]));
         let tracer = opentelemetry_otlp::new_pipeline()
             .tracing()