[hw-7] add metrics, tracing

loms/internal/infra/db/postgres/tracer.go

@@ -0,0 +1,38 @@
+package postgres
+
+import (
+	"context"
+	"strings"
+	"time"
+
+	"route256/loms/internal/infra/grpc/metrics"
+
+	"github.com/jackc/pgx/v5"
+)
+
+type startKey struct{}
+
+type promTracer struct{}
+
+func (promTracer) TraceQueryStart(ctx context.Context, _ *pgx.Conn, _ pgx.TraceQueryStartData) context.Context {
+	return context.WithValue(ctx, startKey{}, time.Now())
+}
+
+func (promTracer) TraceQueryEnd(ctx context.Context, _ *pgx.Conn, data pgx.TraceQueryEndData) {
+	start, _ := ctx.Value(startKey{}).(time.Time)
+
+	sql := strings.TrimSpace(strings.ToLower(data.CommandTag.String()))
+	parts := strings.SplitN(sql, " ", 2)
+	category := "unknown"
+	if len(parts) > 0 {
+		category = parts[0]
+	}
+
+	errLabel := "none"
+	if data.Err != nil {
+		errLabel = "error"
+	}
+
+	metrics.IncDBQueryCount(category, errLabel)
+	metrics.StoreDBQueryDuration(category, errLabel, time.Since(start))
+}