feat(obs): OTLP trace foundation — stable IDs, W3C traceparent, span hierarchy

crates/aisix-core/src/config.rs

@@ -764,6 +764,15 @@ impl RequestIdConfig {
                 if RESERVED_UPSTREAM_HEADERS.contains(&name.as_str()) {
                     return Err(s.clone());
                 }
+                // W3C trace-context headers can't be request-id sources
+                // either (AISIX-Cloud#1279): the resolved id is echoed to
+                // the caller, logged, and sent upstream — adopting the
+                // inbound `traceparent`/`tracestate` value would disclose
+                // the caller's trace context through all three, walking
+                // around the never-forward guard.
+                if matches!(name.as_str(), "traceparent" | "tracestate") {
+                    return Err(s.clone());
+                }
                 Ok(name)
             })
             .collect()

crates/aisix-gateway/src/upstream_headers.rs

@@ -63,6 +63,18 @@ const NEVER_FORWARD_HEADERS: &[&str] = &[
     "te",
     "trailer",
     "transfer-encoding",
+    // W3C trace context (AISIX-Cloud#1279): the caller's `traceparent`
+    // names a span in the CALLER's trace — relayed to a provider it links
+    // the provider's internal telemetry into the caller's tracing backend
+    // and leaks the caller's trace ids to a third party. The gateway is a
+    // fresh hop; provider-side propagation, if ever wanted, is a separate
+    // opt-in that injects the gateway's own context, never the inbound
+    // value. Listed here rather than in RESERVED_UPSTREAM_HEADERS so an
+    // operator's deliberate `default_headers` entry for a trusted
+    // first-party upstream still works — only the client's copy is
+    // blocked.
+    "traceparent",
+    "tracestate",
     "upgrade",
 ];
 
@@ -370,6 +382,32 @@ mod tests {
         assert_eq!(headers["x-keep"], "yes");
     }
 
+    // AISIX-Cloud#1279: the caller's W3C trace context must never reach a
+    // provider — not under a `*` glob, and not even when an allowlist names
+    // the headers outright. The gateway is a fresh tracing hop; a future
+    // provider-side propagation opt-in injects the gateway's OWN context.
+    #[test]
+    fn trace_context_headers_are_never_forwarded() {
+        for allowlist in [&["*"][..], &["traceparent", "tracestate"][..]] {
+            let patterns: Vec<&str> = allowlist.to_vec();
+            let r = overrides(&[], &patterns);
+            let mut headers = HeaderMap::new();
+            let inbound = client(&[
+                (
+                    "traceparent",
+                    "00-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-01",
+                ),
+                ("tracestate", "vendor=x"),
+            ]);
+            let ctx = UpstreamHeaderContext::from_overrides(Some(&r)).with_client_headers(&inbound);
+            apply_request_headers(&mut headers, &ctx);
+            assert!(
+                headers.is_empty(),
+                "trace context leaked under {allowlist:?}: {headers:?}"
+            );
+        }
+    }
+
     #[test]
     fn allowlist_matches_exact_names_and_a_single_glob() {
         let r = overrides(&[], &["Anthropic-Beta", "x-trace-*"]);

crates/aisix-obs/src/lib.rs

@@ -20,6 +20,7 @@ pub mod metrics;
 pub mod otlp;
 pub mod otlp_http_sink;
 pub mod sink;
+pub mod trace;
 pub mod usage;
 
 use std::io::IsTerminal as _;
@@ -41,6 +42,10 @@ pub use sink::{
     PipelineConfig, SinkAck, SinkCapabilities, SinkContent, SinkError, SinkHandle, SinkHealth,
     SinkPipeline, SinkRecord, SinkResult, SinkStatsSnapshot, SCHEMA_VERSION,
 };
+pub use trace::{
+    parse_traceparent, screen_tracestate, RemoteTraceContext, RequestTraceBundle, SpanEmit,
+    SpanRole, TraceEmission, TRACEPARENT_HEADER, TRACESTATE_HEADER,
+};
 pub use usage::{UsageEvent, UsageSink};
 
 #[derive(Debug, thiserror::Error)]