fix: honor faas.invocation_id from non-Lambda instrumentation scopes

Spans created from a custom ActivitySource/Tracer (a scope not in the recognized AWS Lambda instrumentation list) had their faas.invocation_id ignored: process_trace_request only extracted the invocation id from spans in recognized Lambda scopes. When no id is found and the Runtime API proxy fallback is unavailable, the receiver discards the trace ("/v1/traces has no invocation IDs, discarding trace").

Extract faas.invocation_id from spans in any scope for invocation correlation. The handler-span rewrites (rename, kind, reparent) stay limited to recognized Lambda scopes, so non-Lambda spans are correlated but otherwise left untouched.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: parker-edwards

src/otlp/span_mutations.rs

@@ -644,6 +644,19 @@ pub fn process_trace_request(
                 for span in &mut scope_span.spans {
                     add_resource_attributes(span);
                     extract_http_body_logs(span);
+                    // Honor an explicitly set faas.invocation_id even when the span
+                    // comes from a non-Lambda instrumentation scope (e.g. a custom
+                    // ActivitySource/Tracer used for manual instrumentation). This is
+                    // used only to correlate the trace to an invocation; the
+                    // handler-span rewrites (rename, kind, reparent) below stay
+                    // limited to recognized Lambda instrumentation scopes. Without
+                    // this, a manually set faas.invocation_id is ignored and the
+                    // trace can be discarded with "no invocation IDs".
+                    if let Some(invocation_id) = extract_invocation_id(span) {
+                        if !invocation_ids.contains(&invocation_id) {
+                            invocation_ids.push(invocation_id);
+                        }
+                    }
                 }
                 continue;
             }
@@ -670,7 +683,7 @@ pub fn process_trace_request(
 
 #[cfg(test)]
 mod tests {
-    use super::{build_synthetic_trace, StatusCode};
+    use super::{build_synthetic_trace, SpanKind, StatusCode};
     use crate::state::invocation_data::StoredTrace;
     use crate::state::invocation_entry;
     use hyper::{header, Method};
@@ -987,20 +1000,56 @@ mod tests {
 
     #[test]
     #[serial]
-    fn process_trace_request_ignores_non_lambda_scopes() {
-        let invocation_id = "inv-process-6";
+    fn process_trace_request_honors_invocation_id_in_non_lambda_scope_without_rewrite() {
+        // A handler span created from a custom ActivitySource (scope
+        // "<service>.Handler") that manually sets faas.invocation_id. The scope is
+        // not a recognized Lambda instrumentation scope, but the invocation id must
+        // still be honored so the trace is correlated and kept rather than discarded.
+        let invocation_id = "8f3c1d2e-aws-request-id";
         store_event_payload(invocation_id, r#"{"test":"data"}"#);
 
-        let span = make_span_with_invocation(invocation_id);
-        let mut request = make_request_with_scope("other.instrumentation.scope", span);
+        let mut span = make_span_with_invocation(invocation_id);
+        span.name = "GET /orders".to_string();
+        span.kind = SpanKind::Server as i32;
+        let mut request = make_request_with_scope("payments-api.Handler", span);
+        let mut invocation_ids = Vec::new();
+        let mut encoded_body = Vec::new();
+
+        super::process_trace_request(&mut request, &mut invocation_ids, &mut encoded_body);
+
+        // The invocation id is extracted even though the scope is not a Lambda scope.
+        assert_eq!(invocation_ids, vec![invocation_id.to_string()]);
+
+        // ...but the span itself is left untouched: handler-span rewrites stay
+        // limited to recognized Lambda instrumentation scopes.
+        let out = &request.resource_spans[0].scope_spans[0].spans[0];
+        assert_eq!(
+            out.name, "GET /orders",
+            "non-lambda span must not be renamed"
+        );
+        assert_eq!(
+            out.kind,
+            SpanKind::Server as i32,
+            "non-lambda span kind must be preserved"
+        );
+    }
+
+    #[test]
+    #[serial]
+    fn process_trace_request_non_lambda_span_without_invocation_id_adds_no_ids() {
+        let span = Span {
+            name: "GET /".to_string(),
+            ..Default::default()
+        };
+        let mut request = make_request_with_scope("System.Net.Http", span);
         let mut invocation_ids = Vec::new();
         let mut encoded_body = Vec::new();
 
         super::process_trace_request(&mut request, &mut invocation_ids, &mut encoded_body);
 
         assert!(
             invocation_ids.is_empty(),
-            "invocation_ids should remain empty for non-lambda scopes"
+            "a non-lambda span without faas.invocation_id contributes no invocation ids"
         );
     }