[hw-7] add metrics, tracing

loms/internal/infra/grpc/middleware/metrics.go

@@ -0,0 +1,43 @@
+package mw
+
+import (
+	"context"
+	"strings"
+	"time"
+
+	"route256/loms/internal/infra/grpc/metrics"
+
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/status"
+)
+
+const UNKNOWN = "unknown"
+
+func WithMetrics(ctx context.Context, req any, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (resp any, err error) {
+	start := time.Now()
+
+	resp, err = handler(ctx, req)
+
+	// "/pkg.Service/Method"
+	service, method := parseFullMethod(info.FullMethod)
+
+	code := status.Code(err).String()
+
+	metrics.IncRequestHandlerCount(service, method, code)
+	metrics.StoreHandlerRequestDuration(service, method, code, time.Since(start))
+
+	return resp, err
+}
+
+func parseFullMethod(full string) (service, method string) {
+	if full == "" {
+		return UNKNOWN, UNKNOWN
+	}
+	full = strings.TrimPrefix(full, "/")
+
+	slash := strings.Index(full, "/")
+	if slash < 0 {
+		return full, UNKNOWN
+	}
+	return full[:slash], full[slash+1:]
+}