refactor(obs): migrate metrics runtime/schema and tighten migration guards (#2584)

crates/obs/src/metrics/schema/entry/descriptor.rs

@@ -0,0 +1,113 @@
+// Copyright 2024 RustFS Team
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use crate::{MetricName, MetricNamespace, MetricSubsystem, MetricType};
+use std::collections::HashSet;
+
+/// MetricDescriptor - Metric descriptors
+#[allow(dead_code)]
+#[derive(Debug, Clone)]
+pub struct MetricDescriptor {
+    pub name: MetricName,
+    pub metric_type: MetricType,
+    pub help: String,
+    pub variable_labels: Vec<String>,
+    pub namespace: MetricNamespace,
+    pub subsystem: MetricSubsystem,
+
+    // Internal management values
+    label_set: Option<HashSet<String>>,
+}
+
+impl MetricDescriptor {
+    /// Create a new metric descriptor
+    pub fn new(
+        name: MetricName,
+        metric_type: MetricType,
+        help: String,
+        variable_labels: Vec<String>,
+        namespace: MetricNamespace,
+        subsystem: impl Into<MetricSubsystem>, // Modify the parameter type
+    ) -> Self {
+        Self {
+            name,
+            metric_type,
+            help,
+            variable_labels,
+            namespace,
+            subsystem: subsystem.into(),
+            label_set: None,
+        }
+    }
+
+    /// Get the full metric name in Prometheus style: <namespace>_<subsystem>_<name>
+    #[allow(dead_code)]
+    pub fn get_full_metric_name(&self) -> String {
+        let namespace = self.namespace.as_str();
+        let formatted_subsystem = self.subsystem.as_str();
+
+        format!("{}_{}_{}", namespace, formatted_subsystem, self.name.as_str())
+    }
+
+    /// check whether the label is in the label set
+    #[allow(dead_code)]
+    pub fn has_label(&mut self, label: &str) -> bool {
+        self.get_label_set().contains(label)
+    }
+
+    /// Gets a collection of tags and creates them if they don't exist
+    pub fn get_label_set(&mut self) -> &HashSet<String> {
+        if self.label_set.is_none() {
+            let mut set = HashSet::with_capacity(self.variable_labels.len());
+            for label in &self.variable_labels {
+                set.insert(label.clone());
+            }
+            self.label_set = Some(set);
+        }
+        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");
+    }
+}