Fix otel_span_attr merging across config levels (#107).

src/http_module.cpp

@@ -959,6 +959,33 @@ char* mergeLocationConf(ngx_conf_t* cf, void* parent, void* child)
 
     if (conf->spanAttrs.elts == NULL) {
         conf->spanAttrs = prev->spanAttrs;
+    } else if (prev->spanAttrs.elts != NULL) {
+        ngx_array_t merged;
+        if (ngx_array_init(&merged, cf->pool,
+                prev->spanAttrs.nelts + conf->spanAttrs.nelts,
+                sizeof(SpanAttr)) != NGX_OK) {
+            return (char*)NGX_CONF_ERROR;
+        }
+
+        auto prevAttrs = (SpanAttr*)prev->spanAttrs.elts;
+        for (ngx_uint_t i = 0; i < prev->spanAttrs.nelts; i++) {
+            auto attr = (SpanAttr*)ngx_array_push(&merged);
+            if (attr == NULL) {
+                return (char*)NGX_CONF_ERROR;
+            }
+            *attr = prevAttrs[i];
+        }
+
+        auto confAttrs = (SpanAttr*)conf->spanAttrs.elts;
+        for (ngx_uint_t i = 0; i < conf->spanAttrs.nelts; i++) {
+            auto attr = (SpanAttr*)ngx_array_push(&merged);
+            if (attr == NULL) {
+                return (char*)NGX_CONF_ERROR;
+            }
+            *attr = confAttrs[i];
+        }
+
+        conf->spanAttrs = merged;
     }
 
     auto mcf = getMainConf(cf);

tests/test_otel.py

@@ -31,6 +31,7 @@
 
     otel_trace on;
     {{ resource_attrs }}
+    {{ span_attrs or "" }}
 
     server {
         listen       127.0.0.1:18443 ssl;
@@ -40,6 +41,7 @@
         http2 on;
 
         server_name  localhost;
+        {{ server_span_attrs or "" }}
 
         location /ok {
             return 200 "OK";
@@ -123,6 +125,13 @@ def get_attr(span, name):
         return getattr(value, value.WhichOneof("value"))
 
 
+def get_all_attrs(span, name):
+    return [
+        getattr(a.value, a.value.WhichOneof("value"))
+        for a in span.attributes if a.key == name
+    ]
+
+
 @pytest.fixture
 def client(nginx):
     urllib3.disable_warnings(urllib3.exceptions.InsecureRequestWarning)
@@ -329,3 +338,64 @@ def test_tls_export(client, trace_service):
     assert client.get("http://127.0.0.1:18080/ok").status_code == 200
 
     assert trace_service.get_span().name == "/ok"
+
+
+@pytest.mark.parametrize(
+    "nginx_config",
+    [
+        {
+            "span_attrs": """
+                otel_span_attr config.level "http";
+                otel_span_attr http.defined_at "http-block";
+            """,
+            "server_span_attrs": """
+                otel_span_attr config.level "server";
+                otel_span_attr server.defined_at "server-block";
+            """,
+        }
+    ],
+    indirect=True,
+)
+def test_span_attr_merge(client, trace_service):
+    assert client.get("http://127.0.0.1:18080/ok").status_code == 200
+
+    span = trace_service.get_span()
+
+    http_level_attrs = get_all_attrs(span, "config.level")
+    assert "http" in http_level_attrs
+    assert "server" in http_level_attrs
+
+    assert get_attr(span, "http.defined_at") == "http-block"
+    assert get_attr(span, "server.defined_at") == "server-block"
+
+
+@pytest.mark.parametrize(
+    "nginx_config",
+    [
+        {
+            "span_attrs": """
+                otel_span_attr config.level "http";
+                otel_span_attr http.defined_at "http-block";
+            """,
+            "server_span_attrs": """
+                otel_span_attr config.level "server";
+                otel_span_attr server.defined_at "server-block";
+            """,
+        }
+    ],
+    indirect=True,
+)
+def test_span_attr_merge_with_location(client, trace_service):
+    assert client.get("http://127.0.0.1:18080/custom").status_code == 200
+
+    span = trace_service.get_span()
+
+    http_level_attrs = get_all_attrs(span, "config.level")
+    assert "http" in http_level_attrs
+    assert "server" in http_level_attrs
+
+    assert get_attr(span, "http.defined_at") == "http-block"
+    assert get_attr(span, "server.defined_at") == "server-block"
+
+    assert get_attr(span, "http.request.completion") == "OK"
+    assert get_attr(span, "http.request") == "GET /custom HTTP/1.1"