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

crates/obs/src/metrics/schema/notification_target.rs

@@ -0,0 +1,50 @@
+// 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.
+
+#![allow(dead_code)]
+
+use crate::{MetricDescriptor, MetricName, new_counter_md, new_gauge_md, subsystems};
+use std::sync::LazyLock;
+
+pub const TARGET_ID: &str = "target_id";
+pub const TARGET_TYPE: &str = "target_type";
+
+const NOTIFICATION_TARGET_LABELS: [&str; 2] = [TARGET_ID, TARGET_TYPE];
+
+pub static NOTIFICATION_TARGET_FAILED_MESSAGES_MD: LazyLock<MetricDescriptor> = LazyLock::new(|| {
+    new_counter_md(
+        MetricName::NotificationTargetFailedMessages,
+        "Total number of notification messages that permanently failed to send",
+        &NOTIFICATION_TARGET_LABELS,
+        subsystems::NOTIFICATION,
+    )
+});
+
+pub static NOTIFICATION_TARGET_QUEUE_LENGTH_MD: LazyLock<MetricDescriptor> = LazyLock::new(|| {
+    new_gauge_md(
+        MetricName::NotificationTargetQueueLength,
+        "Number of queued notification messages pending delivery",
+        &NOTIFICATION_TARGET_LABELS,
+        subsystems::NOTIFICATION,
+    )
+});
+
+pub static NOTIFICATION_TARGET_TOTAL_MESSAGES_MD: LazyLock<MetricDescriptor> = LazyLock::new(|| {
+    new_counter_md(
+        MetricName::NotificationTargetTotalMessages,
+        "Total number of notification messages successfully delivered",
+        &NOTIFICATION_TARGET_LABELS,
+        subsystems::NOTIFICATION,
+    )
+});