fix(metrics): add path label to HTTP response metrics

docs/getting-started/monitoring.md

@@ -129,7 +129,7 @@ spec:
 |--------|------|-------------|
 | `smg_http_requests_total` | Counter | Requests by method, path |
 | `smg_http_request_duration_seconds` | Histogram | Request latency |
-| `smg_http_responses_total` | Counter | Responses by status_code, error_code |
+| `smg_http_responses_total` | Counter | Responses by path, status_code, error_code |
 | `smg_http_connections_active` | Gauge | Active connections |
 | `smg_http_rate_limit_total` | Counter | Rate limit decisions |
 
@@ -184,6 +184,13 @@ sum(rate(smg_http_responses_total{status_code=~"5.."}[5m]))
 / sum(rate(smg_http_responses_total[5m]))
 ```
 
+**`/v1/responses` Success Rate**
+
+```promql
+sum(rate(smg_http_responses_total{path="/v1/responses",status_code=~"2.."}[5m]))
+/ sum(rate(smg_http_responses_total{path="/v1/responses"}[5m]))
+```
+
 **Time to First Token (TTFT)**
 ```promql
 histogram_quantile(0.5, rate(smg_router_ttft_seconds_bucket[5m]))

docs/reference/metrics.md

@@ -69,18 +69,23 @@ rate(smg_http_request_duration_seconds_sum[5m]) / rate(smg_http_request_duration
 
 ### `smg_http_responses_total`
 
-HTTP responses by status and error code.
+HTTP responses by path, status, and error code.
 
 | Type | Labels |
 |------|--------|
-| Counter | `status_code`, `error_code` |
+| Counter | `path`, `status_code`, `error_code` |
 
 ```promql
 # Error rate (5xx responses)
 sum(rate(smg_http_responses_total{status_code=~"5.."}[5m])) / sum(rate(smg_http_responses_total[5m]))
 
 # Success rate
 sum(rate(smg_http_responses_total{status_code="200"}[5m])) / sum(rate(smg_http_responses_total[5m]))
+
+# Success rate for /v1/responses
+sum(rate(smg_http_responses_total{path="/v1/responses",status_code=~"2.."}[5m]))
+/
+sum(rate(smg_http_responses_total{path="/v1/responses"}[5m]))
 ```
 
 ---

model_gateway/src/middleware/logging.rs

@@ -12,12 +12,9 @@ use tracing::{error, field::Empty, info, info_span, warn, Span};
 use tracing_opentelemetry::OpenTelemetrySpanExt;
 
 use super::{metrics::normalize_path_for_metrics, request_id::RequestId};
-use crate::{
-    observability::{
-        metrics::{method_to_static_str, Metrics},
-        otel_trace::extract_trace_context_http,
-    },
-    routers::error::extract_error_code_from_response,
+use crate::observability::{
+    metrics::{method_to_static_str, Metrics},
+    otel_trace::extract_trace_context_http,
 };
 
 /// Custom span maker that includes request ID
@@ -85,11 +82,6 @@ impl<B> OnResponse<B> for ResponseLogger {
         let status = response.status();
         let status_code = status.as_u16();
 
-        let error_code = extract_error_code_from_response(response);
-
-        // Layer 1: HTTP metrics
-        Metrics::record_http_response(status_code, error_code);
-
         // Record these in the span for structured logging/observability tools
         span.record("status_code", status_code);
         // Use microseconds as integer to avoid format! string allocation

model_gateway/src/middleware/metrics.rs

@@ -15,9 +15,12 @@ use std::{
 use axum::{extract::Request, response::Response};
 use tower::{Layer, Service};
 
-use crate::observability::{
-    inflight_tracker::InFlightRequestTracker,
-    metrics::{method_to_static_str, Metrics},
+use crate::{
+    observability::{
+        inflight_tracker::InFlightRequestTracker,
+        metrics::{method_to_static_str, Metrics},
+    },
+    routers::error::extract_error_code_from_response,
 };
 
 /// Tower Layer for HTTP metrics collection (SMG Layer 1 metrics)
@@ -86,6 +89,11 @@ where
             let response = result?;
 
             let duration = start.elapsed();
+            Metrics::record_http_response(
+                &path,
+                response.status().as_u16(),
+                extract_error_code_from_response(&response),
+            );
             Metrics::record_http_duration(method, &path, duration);
 
             Ok(response)

model_gateway/src/observability/metrics.rs

@@ -162,7 +162,7 @@ pub(crate) fn init_metrics() {
     );
     describe_counter!(
         "smg_http_responses_total",
-        "Total HTTP responses by status_code and error_code"
+        "Total HTTP responses by path, status_code and error_code"
     );
     describe_gauge!(
         "smg_http_connections_active",
@@ -516,11 +516,13 @@ impl Metrics {
     }
 
     /// Record HTTP response.
-    pub fn record_http_response(status_code: u16, error_code: &str) {
+    pub fn record_http_response(path: &str, status_code: u16, error_code: &str) {
+        let path_interned = intern_string(path);
         let status_str: Cow<'static, str> = status_code_to_cow(status_code);
         let error_interned = intern_string(error_code);
         counter!(
             "smg_http_responses_total",
+            "path" => path_interned,
             "status_code" => status_str,
             "error_code" => error_interned
         )