Fix smg_http_requests_total semantics (#15655)

sgl-model-gateway/src/middleware.rs

@@ -308,6 +308,10 @@ impl<B> OnRequest<B> for RequestLogger {
             span.record("request_id", request_id.0.as_str());
         }
 
+        let method = method_to_static_str(request.method().as_str());
+        let path = normalize_path_for_metrics(request.uri().path());
+        Metrics::record_http_request(method, &path);
+
         // Log the request start
         info!(
             target: "sgl_model_gateway::request",
@@ -663,9 +667,6 @@ where
             let response = result?;
 
             let duration = start.elapsed();
-            let status_class = status_to_class(response.status().as_u16());
-
-            Metrics::record_http_request(method, &path, status_class);
             Metrics::record_http_duration(method, &path, duration);
 
             Ok(response)
@@ -673,18 +674,6 @@ where
     }
 }
 
-#[inline]
-fn status_to_class(status: u16) -> &'static str {
-    match status {
-        100..=199 => "1xx",
-        200..=299 => "2xx",
-        300..=399 => "3xx",
-        400..=499 => "4xx",
-        500..=599 => "5xx",
-        _ => "unknown",
-    }
-}
-
 /// Normalize path for metrics to avoid high cardinality.
 /// Replaces dynamic segments (IDs, UUIDs) with `{id}` placeholder.
 /// Only allocates when normalization is needed; uses single-pass with byte offsets.

sgl-model-gateway/src/observability/metrics.rs

@@ -102,7 +102,7 @@ pub fn init_metrics() {
     // Layer 1: HTTP metrics
     describe_counter!(
         "smg_http_requests_total",
-        "Total HTTP requests by method, path, and status"
+        "Total HTTP requests by method and path"
     );
     describe_histogram!(
         "smg_http_request_duration_seconds",
@@ -413,14 +413,13 @@ pub struct StreamingMetricsParams<'a> {
 
 impl Metrics {
     /// Record an HTTP request.
-    /// For best performance, pass static strings (use `method_to_static_str` for method,
+    /// Here we want a metric to directly reflect user's experience ("I am sending a request")
-    /// `status_to_class` for status_class returns static, and cache normalized paths).
+    /// when viewing the router as a blackbox, and is bumped immediately when the request arrives.
-    pub fn record_http_request(method: &'static str, path: &str, status_class: &'static str) {
+    pub fn record_http_request(method: &'static str, path: &str) {
         counter!(
             "smg_http_requests_total",
             "method" => method,
             "path" => path.to_string(),
-            "status" => status_class
         )
         .increment(1);
     }