src/common/metrics.rs (2)

732-750: Centralize and sanitize prefix/name join to ensure exactly one underscore

Malformed names occur when:

• global prefix present but user omits trailing _
• global prefix absent (local "rest"/"grpc" missing separator)
• user sets metrics_prefix = "qdrant" (no _)

Normalize here so all call sites are correct:

-    let name_with_prefix = prefix
-        .map(|prefix| format!("{prefix}{name}"))
-        .unwrap_or_else(|| name.to_string());
+    let name_with_prefix = match prefix {
+        Some(p) if !p.is_empty() => {
+            let p = p.trim();
+            if p.ends_with('_') || name.starts_with('_') {
+                format!("{p}{name}")
+            } else {
+                format!("{p}_{name}")
+            }
+        }
+        _ => name.to_string(),
+    };

This yields qdrant_app_info, qdrant_rest_responses_total, and handles a user-provided "qdrant" or "qdrant_" identically.

---

669-675: Prefix composition misses underscore when global_prefix is None

unwrap_or_else(|| prefix.to_string()) produces "restresponses_total". Normalize prefix joining centrally (see next comment) and avoid hardcoding underscores here.

Option A (prefer): Delegate underscore insertion to metric_family and stop adding a trailing _ here.

-        let prefix = global_prefix
-            .map(|global_prefix| format!("{global_prefix}{prefix}_"))
-            .unwrap_or_else(|| prefix.to_string());
+        let prefix = global_prefix
+            .map(|global_prefix| format!("{global_prefix}{prefix}"))
+            .unwrap_or_else(|| prefix.to_string());

Option B: If you keep local handling, ensure the None branch also adds _:

-            .unwrap_or_else(|| prefix.to_string());
+            .unwrap_or_else(|| format!("{prefix}_"));

config/config.yaml (1)

300-304: Good: option is documented and disabled by default

Consider clarifying allowed characters and underscore behavior to reduce user error.

Suggested wording:

# Prefix for metric names in /metrics. Must match ^[a-zA-Z_:][a-zA-Z0-9_:]*$.
# If it doesn't end with '_', one will be inserted automatically.
# Recommended: "qdrant_"
# metrics_prefix: qdrant_

src/actix/api/service_api.rs (2)

7-8: Unify actix-web import style for consistency

Imports mix web::{Data, Query} with web::... usage. Prefer one style. Suggest using web::Data and web::Query everywhere to match the rest of the file.

-use actix_web::web::{Data, Query};
+// use web::Data and web::Query consistently via the `web` module
 // ...
-async fn metrics(
-    telemetry_collector: web::Data<Mutex<TelemetryCollector>>,
-    params: Query<MetricsParam>,
-    config: Data<ServiceConfig>,
+async fn metrics(
+    telemetry_collector: web::Data<Mutex<TelemetryCollector>>,
+    params: web::Query<MetricsParam>,
+    config: web::Data<ServiceConfig>,
     ActixAccess(access): ActixAccess,
 ) -> HttpResponse {

Also applies to: 69-74

---

95-99: Trim and ignore empty metrics_prefix values

Defensive: treat whitespace-only strings as unset to avoid odd names like " _app_info".

-    let metrics_prefix = config.metrics_prefix.as_deref();
+    let metrics_prefix = config
+        .metrics_prefix
+        .as_deref()
+        .map(str::trim)
+        .filter(|s| !s.is_empty());

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