fix: 接线 Prometheus 指标到连接与投递事件

internal/metrics/sample.go

@@ -0,0 +1,36 @@
+package metrics
+
+import (
+	"context"
+	"database/sql"
+)
+
+// SampleStoreGauges 按库内真实计数刷新端总数、待投递、定时消息（无对应行则为 0）。
+func SampleStoreGauges(ctx context.Context, r *Registry, db *sql.DB) error {
+	if r == nil || db == nil {
+		return nil
+	}
+	var endpoints, pending, scheduled int
+	if err := db.QueryRowContext(ctx, `SELECT COUNT(*) FROM endpoints`).Scan(&endpoints); err != nil {
+		return err
+	}
+	if err := db.QueryRowContext(ctx, `SELECT COUNT(*) FROM deliveries WHERE state = 'pending'`).Scan(&pending); err != nil {
+		return err
+	}
+	if err := db.QueryRowContext(ctx, `SELECT COUNT(*) FROM messages WHERE state = 'scheduled'`).Scan(&scheduled); err != nil {
+		return err
+	}
+	r.EndpointsTotal.Set(float64(endpoints))
+	r.DeliveriesPending.Set(float64(pending))
+	r.MessagesScheduled.Set(float64(scheduled))
+	return nil
+}
+
+// SampleQueues 刷新写队列与密码哈希排队长度（传入当前真实长度，不做估算）。
+func SampleQueues(r *Registry, writeQueueLen, passwordHashQueueLen int) {
+	if r == nil {
+		return
+	}
+	r.WriteQueueLength.Set(float64(writeQueueLen))
+	r.PasswordHashQueue.Set(float64(passwordHashQueueLen))
+}