⚗️ Continue try connecting trace

Signed-off-by: Evaline Ju <69598118+evaline-ju@users.noreply.github.com>

Author: evaline-ju

a2a/weather_service/pyproject.toml

@@ -18,6 +18,8 @@ dependencies = [
     "langchain-mcp-adapters>=0.1.0",
     "python-keycloak>=5.5.1",
     "opentelemetry-exporter-otlp",
+    # Auto-instrument httpx so outgoing MCP tool calls propagate traceparent
+    "opentelemetry-instrumentation-httpx>=0.49b0",
     # OpenTelemetry GenAI semantic convention instrumentation
     # Emits spans with gen_ai.* attributes for MLflow compatibility
     "opentelemetry-instrumentation-openai>=0.34b0",

a2a/weather_service/src/weather_service/agent.py

@@ -119,18 +119,10 @@ async def execute(self, context: RequestContext, event_queue: EventQueue):
         # Test MCP connection first
         logger.info(f'Attempting to connect to MCP server at: {os.getenv("MCP_URL", "http://localhost:8000/sse")}')
 
-        # Extract current trace context for propagation to Envoy/MCP
-        traceparent = None
-        root_span = get_root_span()
-        if root_span and root_span.is_recording():
-            span_context = root_span.get_span_context()
-            if span_context.is_valid:
-                # Format traceparent according to W3C Trace Context spec
-                # Format: version-trace_id-span_id-trace_flags
-                traceparent = f"00-{format(span_context.trace_id, '032x')}-{format(span_context.span_id, '016x')}-{format(span_context.trace_flags, '02x')}"
-                logger.info(f'Propagating trace context to MCP: {traceparent}')
-
-        mcpclient = get_mcpclient(traceparent=traceparent)
+        # Trace context propagation to MCP gateway is handled automatically
+        # by opentelemetry-instrumentation-httpx, which injects the current
+        # span's traceparent header on every outgoing httpx request.
+        mcpclient = get_mcpclient()
 
         # Try to get tools to verify connection
         try:

a2a/weather_service/src/weather_service/graph.py

@@ -12,27 +12,18 @@
 class ExtendedMessagesState(MessagesState):
      final_answer: str = ""
 
-def get_mcpclient(traceparent: str | None = None):
-    """
-    Create an MCP client with optional trace context propagation.
+def get_mcpclient():
+    """Create an MCP client.
 
-    Args:
-        traceparent: W3C Trace Context traceparent header value
-                    Format: "00-{trace-id}-{parent-id}-{trace-flags}"
+    Trace context propagation (traceparent headers) to the MCP gateway is
+    handled automatically by opentelemetry-instrumentation-httpx, which
+    injects the current span's context on every outgoing HTTP request.
     """
-    server_config = {
-        "url": os.getenv("MCP_URL", "http://localhost:8000/mcp"),
-        "transport": os.getenv("MCP_TRANSPORT", "streamable_http"),
-    }
-
-    # Add traceparent header if provided for distributed tracing through Envoy
-    if traceparent:
-        server_config["headers"] = {
-            "traceparent": traceparent
-        }
-
     return MultiServerMCPClient({
-        "math": server_config
+        "math": {
+            "url": os.getenv("MCP_URL", "http://localhost:8000/mcp"),
+            "transport": os.getenv("MCP_TRANSPORT", "streamable_http"),
+        }
     })
 
 async def get_graph(client) -> StateGraph:

a2a/weather_service/src/weather_service/observability.py

@@ -125,6 +125,18 @@ def setup_observability() -> None:
         W3CBaggagePropagator(),
     ]))
 
+    # Instrument httpx for automatic traceparent propagation on outgoing requests.
+    # This is critical for distributed tracing: langchain-mcp-adapters uses httpx
+    # for streamable_http transport, so each MCP tool call will automatically carry
+    # the current span's traceparent header to the MCP gateway (Envoy).
+    try:
+        from opentelemetry.instrumentation.httpx import HTTPXClientInstrumentor
+        HTTPXClientInstrumentor().instrument()
+        logger.info("httpx instrumented for automatic trace context propagation")
+    except ImportError:
+        logger.warning("opentelemetry-instrumentation-httpx not available - "
+                       "MCP tool calls will not propagate trace context")
+
     # Instrument OpenAI for GenAI semantic conventions
     try:
         from opentelemetry.instrumentation.openai import OpenAIInstrumentor
@@ -421,10 +433,12 @@ async def tracing_middleware(request: Request, call_next):
         except Exception as e:
             logger.debug(f"Could not parse request body: {e}")
 
-        # Break parent chain to make this a true root span
-        # Without this, the span would inherit parent from W3C Trace Context headers
-        empty_ctx = context.Context()
-        detach_token = context.attach(empty_ctx)
+        # Extract incoming W3C Trace Context from request headers.
+        # If the request carries a traceparent (e.g., from Envoy/MCP gateway or
+        # an upstream orchestrator), the root span becomes a child of that trace.
+        # This is what connects the agent's spans to the MCP gateway's spans.
+        incoming_ctx = extract(dict(request.headers))
+        detach_token = context.attach(incoming_ctx)
 
         try:
             # Create root span with correct GenAI naming convention