in_opentelemetry: return not found for invalid endpoint

plugins/in_opentelemetry/opentelemetry_prot.c

@@ -252,6 +252,9 @@ static int send_response_ng(struct flb_http_response *response,
     else if (http_status == 400) {
         flb_http_response_set_message(response, "Bad Request");
     }
+    else if (http_status == 404) {
+        flb_http_response_set_message(response, "Not Found");
+    }
 
     if (message != NULL) {
         flb_http_response_set_body(response,
@@ -828,7 +831,7 @@ int opentelemetry_prot_handle_ng(struct flb_http_request *request,
         grpc_request = FLB_TRUE;
     }
     else {
-        send_response_ng(response, 400, "error: invalid endpoint\n");
+        send_response_ng(response, 404, "error: invalid endpoint\n");
         return -1;
     }
 

tests/integration/scenarios/in_opentelemetry/tests/test_in_opentelemetry_001.py

@@ -1258,6 +1258,27 @@ def test_in_opentelemetry_protocol_matrix(case, signal_type, json_input, endpoin
     assert len(response_payload) > 0
 
 
+def test_in_opentelemetry_http2_invalid_endpoint_returns_404():
+    service = Service(IN_OPENTELEMETRY_PROTOCOL_CONFIGS["http2_cleartext"])
+    service.start()
+
+    result = run_curl_request(
+        f"http://localhost:{service.flb_listener_port}/v1/invalid",
+        b"invalid payload",
+        headers=["Content-Type: application/x-protobuf"],
+        http_mode="http2-prior-knowledge",
+    )
+
+    service.stop()
+
+    assert result["status_code"] == 404
+    assert result["http_version"] == "2"
+    assert result["body"] == "error: invalid endpoint\n"
+    assert len(data_storage["logs"]) == 0
+    assert len(data_storage["metrics"]) == 0
+    assert len(data_storage["traces"]) == 0
+
+
 # This test is branch-specific coverage for the generic HTTP listener worker mode.
 # It does three things:
 # 1. enables http_server.workers on the in_opentelemetry listener,