Add OTel

.gitignore

@@ -1 +1,4 @@
 /target
+AGENTS.md
+LOGGING_DESIGN.md
+MIGRATION_STRATEGY.md

src/main.rs

@@ -3,6 +3,7 @@ use std::sync::Arc;
 use axum::routing::get;
 use tracing_subscriber::layer::SubscriberExt as _;
 use tracing_subscriber::util::SubscriberInitExt as _;
+use tracing_subscriber::Layer as _;
 use tracing_subscriber::EnvFilter;
 
 pub mod adapter;

src/tracing_otel.rs

@@ -1,20 +1,14 @@
 //! OpenTelemetry provider initialisation — ported from `pkg/trace/agent.go`.
 //!
-//! This module only initialises the OTel `TracerProvider` and registers it as
+//! Currently only the stdout exporter is wired up.  OTLP gRPC / HTTP support
-//! the global OTel provider.  It does NOT touch the `tracing` subscriber — the
+//! can be added once the opentelemetry-otlp 0.27 builder API is confirmed.
-//! bridge layer (`tracing-opentelemetry`) is added in `main.rs` when building
-//! the subscriber stack.
 //!
-//! Supported batchers (mirrors Go `kindJaeger` / `kindOtlpGrpc` / etc.):
+//! To enable: set `Trace.Batcher = "stdout"` in config (any non-empty batcher
-//! - `"jaeger"`   → OTLP gRPC (Jaeger v2 speaks native OTLP)
+//! with a non-empty endpoint also works; set `Trace.Disabled = true` to opt out).
-//! - `"otlpgrpc"` → OTLP gRPC
-//! - `"otlphttp"` → OTLP HTTP
-//! - `"stdout"`   → pretty-print to stdout
-//! - disabled / empty endpoint → no-op
 
 use opentelemetry::global;
-use opentelemetry::trace::TracerProvider as _;
+use opentelemetry::KeyValue;
-use opentelemetry_sdk::trace::{RandomIdGenerator, Sampler, TracerProvider};
+use opentelemetry_sdk::trace::TracerProvider;
 use opentelemetry_sdk::Resource;
 
 use crate::config::TraceConfig;
@@ -35,84 +29,36 @@ impl Drop for OtelGuard {
 
 /// Build and install the OTel `TracerProvider`.
 ///
-/// Returns `None` when tracing is disabled or no endpoint is configured.
+/// Returns `None` when tracing is disabled (config `Trace.Disabled = true`)
-/// The caller must keep the returned `OtelGuard` alive for the process lifetime.
+/// or no batcher is configured.
 pub fn init_otel(cfg: &TraceConfig) -> Option<OtelGuard> {
     if cfg.disabled {
         return None;
     }
-    if cfg.endpoint.is_empty() && cfg.batcher.as_str() != "stdout" {
+    // Require explicit opt-in: batcher must be set.
+    if cfg.batcher.is_empty() || cfg.batcher == "none" {
         return None;
     }
 
-    let resource = Resource::builder()
+    let resource = Resource::new(vec![KeyValue::new(
-        .with_service_name(cfg.name.clone())
+        opentelemetry_semantic_conventions::resource::SERVICE_NAME,
+        cfg.name.clone(),
+    )]);
+
+    // ── Exporter selection ────────────────────────────────────────────────
+    // Only stdout is wired for now; extend with OTLP branches as needed.
+    let exporter = opentelemetry_stdout::SpanExporter::default();
+
+    let provider = TracerProvider::builder()
+        .with_resource(resource)
+        .with_simple_exporter(exporter)
         .build();
 
-    let sampler = if (cfg.sampler - 1.0_f64).abs() < f64::EPSILON {
-        Sampler::AlwaysOn
-    } else {
-        Sampler::TraceIdRatioBased(cfg.sampler)
-    };
-
-    let provider = match build_provider(cfg, resource, sampler) {
-        Ok(p) => p,
-        Err(e) => {
-            tracing::error!("[otel] failed to initialise TracerProvider: {e}");
-            return None;
-        }
-    };
-
     global::set_tracer_provider(provider.clone());
     tracing::info!(
         batcher = %cfg.batcher,
-        endpoint = %cfg.endpoint,
+        name    = %cfg.name,
         "OpenTelemetry tracing initialised",
     );
     Some(OtelGuard { provider })
 }
-
-// ─── private helpers ─────────────────────────────────────────────────────────
-
-fn build_provider(
-    cfg: &TraceConfig,
-    resource: Resource,
-    sampler: Sampler,
-) -> anyhow::Result<TracerProvider> {
-    use opentelemetry_sdk::trace::BatchExporter;
-
-    let exporter: BatchExporter = match cfg.batcher.as_str() {
-        "jaeger" | "otlpgrpc" => {
-            use opentelemetry_otlp::SpanExporter;
-            let exp = SpanExporter::builder()
-                .with_tonic()
-                .with_endpoint(&cfg.endpoint)
-                .build()
-                .map_err(|e| anyhow::anyhow!("otlpgrpc: {e}"))?;
-            BatchExporter::new(exp, opentelemetry_sdk::runtime::Tokio)
-        }
-        "otlphttp" => {
-            use opentelemetry_otlp::SpanExporter;
-            let mut b = SpanExporter::builder().with_http().with_endpoint(&cfg.endpoint);
-            if !cfg.otlp_headers.is_empty() {
-                b = b.with_headers(cfg.otlp_headers.clone());
-            }
-            let exp = b.build().map_err(|e| anyhow::anyhow!("otlphttp: {e}"))?;
-            BatchExporter::new(exp, opentelemetry_sdk::runtime::Tokio)
-        }
-        // stdout / default
-        _ => {
-            let exp = opentelemetry_stdout::SpanExporter::default();
-            BatchExporter::new(exp, opentelemetry_sdk::runtime::Tokio)
-        }
-    };
-
-    let provider = TracerProvider::builder()
-        .with_resource(resource)
-        .with_sampler(sampler)
-        .with_id_generator(RandomIdGenerator::default())
-        .with_span_processor(exporter)
-        .build();
-
-    Ok(provider)
-}