[model-gateway] add OTEL integration to grpc router (#14671)

sgl-model-gateway/tests/otel_tracing_test.rs

@@ -24,9 +24,11 @@ use sgl_model_gateway::{
     routers::RouterFactory,
 };
 use tokio::sync::oneshot;
+use tonic::metadata::MetadataMap;
 use tonic_v12::{transport::Server, Request as TonicRequest, Response, Status};
 use tower::ServiceExt;
 use tracing::info_span;
+use tracing_subscriber::prelude::*;
 
 #[derive(Clone)]
 struct TestOtelCollector {
@@ -131,14 +133,22 @@ async fn test_router_with_tracing() {
         .enable_trace(&collector_endpoint)
         .build_unchecked();
 
-    // 4. Initialize the OTLP client
-    let init_result = otel_trace::otel_tracing_init(true, Some(&collector_endpoint));
-    assert!(
-        init_result.is_ok(),
-        "Failed to initialize OTEL: {:?}",
-        init_result.err()
-    );
-    println!("OpenTelemetry initialized successfully");
+    // 4. Initialize the OTLP client (check if already initialized by another test)
+    let otel_initialized_by_this_test = if !otel_trace::is_otel_enabled() {
+        let init_result = otel_trace::otel_tracing_init(true, Some(&collector_endpoint));
+        assert!(
+            init_result.is_ok(),
+            "Failed to initialize OTEL: {:?}",
+            init_result.err()
+        );
+        println!("OpenTelemetry initialized successfully");
+        true
+    } else {
+        println!(
+            "OpenTelemetry already initialized by previous test (spans will go to that collector)"
+        );
+        false
+    };
 
     let trace_config = TraceConfig {
         enable_trace: true,
@@ -232,14 +242,23 @@ async fn test_router_with_tracing() {
     let span_count = collector.get_span_count();
     println!("Total spans received by collector: {}", span_count);
 
-    assert!(
-        span_count == 2,
-        "Expected to receive at least 2 span, but got {}. \
-        This indicates that tracing data is not being exported to the OTLP collector.",
-        span_count
-    );
-
-    println!("Test passed! Collector received {} spans", span_count);
+    // Only assert span count if we initialized OTEL with our own collector
+    // When OTEL was pre-initialized by another test, spans go to that collector instead
+    if otel_initialized_by_this_test {
+        assert!(
+            span_count == 2,
+            "Expected to receive at least 2 span, but got {}. \
+            This indicates that tracing data is not being exported to the OTLP collector.",
+            span_count
+        );
+        println!("Test passed! Collector received {} spans", span_count);
+    } else {
+        println!(
+            "Skipping span count assertion - OTEL was pre-initialized by another test. \
+            Spans went to that collector. Received {} spans on this test's collector.",
+            span_count
+        );
+    }
 
     // 13. cleanup
     let _ = shutdown_tx.send(());
@@ -247,3 +266,115 @@ async fn test_router_with_tracing() {
 
     println!("Cleanup completed");
 }
+
+// ============================================================================
+// gRPC Trace Context Injection Tests
+// ============================================================================
+
+/// Comprehensive test for gRPC trace context injection.
+///
+/// This test validates:
+/// 1. W3C trace context headers are properly injected into gRPC metadata
+/// 2. traceparent format is correct (version-traceid-spanid-flags)
+/// 3. All metadata keys are lowercase (gRPC requirement)
+///
+/// Note: This test handles the case where OTEL may already be initialized
+/// by a previous test (since tests run sequentially with #[serial]).
+#[tokio::test]
+#[serial]
+async fn test_grpc_trace_context_injection() {
+    // 1. Start the OTLP collector (needed even if OTEL is already initialized,
+    //    as a target for any spans that might be exported)
+    let port = pick_unused_port().expect("Failed to pick unused port");
+    let (shutdown_tx, shutdown_rx) = oneshot::channel();
+    let _collector = start_collector(port, shutdown_rx)
+        .await
+        .expect("Failed to start collector");
+    let collector_endpoint = format!("0.0.0.0:{}", port);
+
+    // 2. Initialize OTEL if not already enabled
+    // Note: otel_tracing_init will fail if already initialized (OnceLock),
+    // but that's fine - we just need OTEL to be enabled
+    let already_enabled = otel_trace::is_otel_enabled();
+    if !already_enabled {
+        let init_result = otel_trace::otel_tracing_init(true, Some(&collector_endpoint));
+        assert!(
+            init_result.is_ok(),
+            "Failed to initialize OTEL: {:?}",
+            init_result.err()
+        );
+    }
+
+    // Verify OTEL is enabled (either from this test or a previous one)
+    assert!(otel_trace::is_otel_enabled(), "OTEL should be enabled");
+
+    // 3. Set up tracing subscriber with OTEL layer
+    let otel_layer = otel_trace::get_otel_layer().expect("Failed to get OTEL layer");
+    let subscriber = tracing_subscriber::registry().with(otel_layer);
+
+    // 4. Test within a span context
+    tracing::subscriber::with_default(subscriber, || {
+        // Create a span that will be exported to OTEL
+        let span = info_span!(target: "sgl_model_gateway::otel-trace", "test_grpc_span");
+        let _guard = span.enter();
+
+        // Create empty gRPC metadata
+        let mut metadata = MetadataMap::new();
+
+        // Inject trace context
+        otel_trace::inject_trace_context_grpc(&mut metadata);
+
+        // === Test 1: Verify traceparent header was injected ===
+        let traceparent = metadata.get("traceparent");
+        assert!(
+            traceparent.is_some(),
+            "traceparent header should be present in gRPC metadata"
+        );
+
+        // === Test 2: Verify traceparent format (version-traceid-spanid-flags) ===
+        let traceparent_value = traceparent.unwrap().to_str().unwrap();
+        let parts: Vec<&str> = traceparent_value.split('-').collect();
+        assert_eq!(
+            parts.len(),
+            4,
+            "traceparent should have 4 parts: version-traceid-spanid-flags"
+        );
+        assert_eq!(parts[0], "00", "traceparent version should be 00");
+        assert_eq!(parts[1].len(), 32, "trace ID should be 32 hex characters");
+        assert_eq!(parts[2].len(), 16, "span ID should be 16 hex characters");
+
+        println!("Successfully injected traceparent: {}", traceparent_value);
+
+        // === Test 3: Verify all keys are lowercase (gRPC metadata requirement) ===
+        for key_and_value in metadata.iter() {
+            match key_and_value {
+                tonic::metadata::KeyAndValueRef::Ascii(key, _) => {
+                    let key_str = key.as_str();
+                    assert_eq!(
+                        key_str,
+                        key_str.to_lowercase(),
+                        "gRPC metadata key '{}' should be lowercase",
+                        key_str
+                    );
+                }
+                tonic::metadata::KeyAndValueRef::Binary(key, _) => {
+                    let key_str = key.as_str();
+                    assert_eq!(
+                        key_str,
+                        key_str.to_lowercase(),
+                        "gRPC metadata key '{}' should be lowercase",
+                        key_str
+                    );
+                }
+            }
+        }
+
+        println!("All gRPC metadata keys are lowercase as required");
+    });
+
+    // Cleanup - don't shutdown OTEL since tests share global state (OnceLock)
+    // and other tests may need to use the already-initialized OTEL
+    let _ = shutdown_tx.send(());
+
+    println!("test_grpc_trace_context_injection: All assertions passed!");
+}