fix(metrics): use Prometheus-compatible metric names (#2312) (#2317)

Signed-off-by: Shunchao Hu <ankohuu@gmail.com>

crates/metrics/src/collectors/system_cpu.rs

@@ -123,7 +123,7 @@ mod tests {
         assert_eq!(metrics.len(), 8);
 
         // Verify that metric names are properly generated from descriptors
-        assert!(metrics.iter().all(|m| m.name.starts_with("gauge.rustfs_system_cpu_")));
+        assert!(metrics.iter().all(|m| m.name.starts_with("rustfs_system_cpu_")));
     }
 
     #[test]

crates/metrics/src/collectors/system_memory.rs

@@ -122,7 +122,7 @@ mod tests {
         report_metrics(&metrics);
 
         assert_eq!(metrics.len(), 8);
-        assert!(metrics.iter().all(|m| m.name.starts_with("gauge.rustfs_system_memory_")));
+        assert!(metrics.iter().all(|m| m.name.starts_with("rustfs_system_memory_")));
     }
 
     #[test]

crates/metrics/src/metrics_type/entry/descriptor.rs

@@ -51,14 +51,13 @@ impl MetricDescriptor {
         }
     }
 
-    /// Get the full metric name, including the prefix and formatting path
+    /// Get the full metric name in Prometheus style: <namespace>_<subsystem>_<name>
     #[allow(dead_code)]
     pub fn get_full_metric_name(&self) -> String {
-        let prefix = self.metric_type.as_prom();
         let namespace = self.namespace.as_str();
         let formatted_subsystem = self.subsystem.as_str();
 
-        format!("{}{}_{}_{}", prefix, namespace, formatted_subsystem, self.name.as_str())
+        format!("{}_{}_{}", namespace, formatted_subsystem, self.name.as_str())
     }
 
     /// check whether the label is in the label set
@@ -79,3 +78,36 @@ impl MetricDescriptor {
         self.label_set.as_ref().unwrap()
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn full_metric_name_uses_prometheus_convention_without_type_prefix() {
+        let descriptor = MetricDescriptor::new(
+            MetricName::ApiRequestsTotal,
+            MetricType::Counter,
+            "test help".to_string(),
+            vec![],
+            MetricNamespace::RustFS,
+            MetricSubsystem::ApiRequests,
+        );
+
+        assert_eq!(descriptor.get_full_metric_name(), "rustfs_api_requests_total");
+    }
+
+    #[test]
+    fn full_metric_name_formats_custom_subsystems_without_type_prefix() {
+        let descriptor = MetricDescriptor::new(
+            MetricName::Custom("latency_seconds".to_string()),
+            MetricType::Histogram,
+            "test help".to_string(),
+            vec![],
+            MetricNamespace::RustFS,
+            MetricSubsystem::new("/custom/path-metrics"),
+        );
+
+        assert_eq!(descriptor.get_full_metric_name(), "rustfs_custom_path_metrics_latency_seconds");
+    }
+}

crates/metrics/src/metrics_type/entry/mod.rs

@@ -110,7 +110,7 @@ mod tests {
         assert_eq!(histogram_md.subsystem, MetricSubsystem::ApiRequests);
 
         // Verify that the full metric name generated is formatted correctly
-        assert_eq!(histogram_md.get_full_metric_name(), "histogram.rustfs_api_requests_seconds_distribution");
+        assert_eq!(histogram_md.get_full_metric_name(), "rustfs_api_requests_seconds_distribution");
 
         // Tests use custom subsystems
         let custom_histogram_md = new_histogram_md(
@@ -123,7 +123,7 @@ mod tests {
         // Verify the custom name and subsystem
         assert_eq!(
             custom_histogram_md.get_full_metric_name(),
-            "histogram.rustfs_custom_path_metrics_custom_latency_distribution"
+            "rustfs_custom_path_metrics_custom_latency_distribution"
         );
     }
 }

crates/metrics/src/metrics_type/entry/subsystem.rs

@@ -233,7 +233,7 @@ mod tests {
             MetricSubsystem::ApiRequests,
         );
 
-        assert_eq!(md.get_full_metric_name(), "counter.rustfs_api_requests_total");
+        assert_eq!(md.get_full_metric_name(), "rustfs_api_requests_total");
 
         let custom_md = MetricDescriptor::new(
             MetricName::Custom("test_metric".to_string()),
@@ -244,6 +244,6 @@ mod tests {
             MetricSubsystem::new("/custom/path-with-dash"),
         );
 
-        assert_eq!(custom_md.get_full_metric_name(), "gauge.rustfs_custom_path_with_dash_test_metric");
+        assert_eq!(custom_md.get_full_metric_name(), "rustfs_custom_path_with_dash_test_metric");
     }
 }