feat: sync current progress (P0 hardening + P1 observability + deploy docs/systemd)

internal/metrics/metrics.go

@@ -0,0 +1,63 @@
+package metrics
+
+import (
+	"strconv"
+	"time"
+
+	"github.com/gin-gonic/gin"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+)
+
+var (
+	HTTPRequestsTotal = promauto.NewCounterVec(
+		prometheus.CounterOpts{Name: "http_requests_total", Help: "Total HTTP requests."},
+		[]string{"method", "path", "status"},
+	)
+	HTTPRequestDuration = promauto.NewHistogramVec(
+		prometheus.HistogramOpts{Name: "http_request_duration_seconds", Help: "HTTP request latency.", Buckets: prometheus.DefBuckets},
+		[]string{"method", "path", "status"},
+	)
+
+	ReminderSendTotal = promauto.NewCounterVec(
+		prometheus.CounterOpts{Name: "reminder_send_total", Help: "Reminder delivery results."},
+		[]string{"status"},
+	)
+	ReminderRetryTotal = promauto.NewCounter(
+		prometheus.CounterOpts{Name: "reminder_retry_total", Help: "Reminder retry count."},
+	)
+
+	DBQueryDuration = promauto.NewHistogramVec(
+		prometheus.HistogramOpts{Name: "db_query_duration_seconds", Help: "DB query duration.", Buckets: prometheus.DefBuckets},
+		[]string{"op", "table", "success"},
+	)
+)
+
+func init() {
+	ReminderSendTotal.WithLabelValues("sent").Add(0)
+	ReminderSendTotal.WithLabelValues("failed").Add(0)
+	ReminderRetryTotal.Add(0)
+	DBQueryDuration.WithLabelValues("scan_pending", "reminders", "true").Observe(0)
+}
+
+func ObserveHTTP(c *gin.Context, start time.Time) {
+	path := c.FullPath()
+	if path == "" {
+		path = c.Request.URL.Path
+	}
+	status := strconv.Itoa(c.Writer.Status())
+	labels := []string{c.Request.Method, path, status}
+	HTTPRequestsTotal.WithLabelValues(labels...).Inc()
+	HTTPRequestDuration.WithLabelValues(labels...).Observe(time.Since(start).Seconds())
+}
+
+func ObserveDB(op, table string, success bool, dur time.Duration) {
+	if table == "" {
+		table = "unknown"
+	}
+	s := "false"
+	if success {
+		s = "true"
+	}
+	DBQueryDuration.WithLabelValues(op, table, s).Observe(dur.Seconds())
+}