feat(go): add platform principles and health probes

go/vehicle-gateway/internal/health/health.go

@@ -0,0 +1,132 @@
+package health
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"net/http"
+	"strings"
+	"time"
+)
+
+type Check struct {
+	Name  string
+	Check func(context.Context) error
+}
+
+type Handler struct {
+	service string
+	checks  []Check
+}
+
+type Logger interface {
+	Info(string, ...any)
+	Error(string, ...any)
+}
+
+func NewHandler(service string, checks []Check) *Handler {
+	service = strings.TrimSpace(service)
+	if service == "" {
+		service = "vehicle-service"
+	}
+	return &Handler{service: service, checks: checks}
+}
+
+func NewMux(service string, checks []Check) *http.ServeMux {
+	mux := http.NewServeMux()
+	handler := NewHandler(service, checks)
+	mux.Handle("/healthz", handler)
+	mux.Handle("/readyz", handler)
+	return mux
+}
+
+func NewServer(addr string, service string, checks []Check) *http.Server {
+	addr = strings.TrimSpace(addr)
+	if addr == "" {
+		return nil
+	}
+	return &http.Server{
+		Addr:              addr,
+		Handler:           NewMux(service, checks),
+		ReadHeaderTimeout: 5 * time.Second,
+	}
+}
+
+func Start(ctx context.Context, logger Logger, server *http.Server) {
+	if server == nil {
+		return
+	}
+	go func() {
+		<-ctx.Done()
+		shutdownCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+		defer cancel()
+		_ = server.Shutdown(shutdownCtx)
+	}()
+	go func() {
+		if logger != nil {
+			logger.Info("health server started", "addr", server.Addr)
+		}
+		if err := server.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) && logger != nil {
+			logger.Error("health server failed", "error", err)
+		}
+	}()
+}
+
+func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	if r.Method != http.MethodGet {
+		writeHealth(w, http.StatusMethodNotAllowed, map[string]any{"error": "method not allowed"})
+		return
+	}
+	path := strings.Trim(r.URL.Path, "/")
+	if path != "healthz" && path != "readyz" {
+		writeHealth(w, http.StatusNotFound, map[string]any{"error": "route not found"})
+		return
+	}
+	if path == "healthz" {
+		writeHealth(w, http.StatusOK, map[string]any{
+			"service": h.service,
+			"status":  "ok",
+			"time":    time.Now().UTC().Format(time.RFC3339),
+		})
+		return
+	}
+	h.writeReadiness(w, r)
+}
+
+func (h *Handler) writeReadiness(w http.ResponseWriter, r *http.Request) {
+	ctx, cancel := context.WithTimeout(r.Context(), 2*time.Second)
+	defer cancel()
+
+	status := "ok"
+	code := http.StatusOK
+	checks := make(map[string]any, len(h.checks))
+	for _, check := range h.checks {
+		name := strings.TrimSpace(check.Name)
+		if name == "" {
+			continue
+		}
+		if check.Check == nil {
+			checks[name] = map[string]any{"status": "ok"}
+			continue
+		}
+		if err := check.Check(ctx); err != nil {
+			status = "degraded"
+			code = http.StatusServiceUnavailable
+			checks[name] = map[string]any{"status": "error", "error": err.Error()}
+			continue
+		}
+		checks[name] = map[string]any{"status": "ok"}
+	}
+	writeHealth(w, code, map[string]any{
+		"service": h.service,
+		"status":  status,
+		"time":    time.Now().UTC().Format(time.RFC3339),
+		"checks":  checks,
+	})
+}
+
+func writeHealth(w http.ResponseWriter, status int, payload map[string]any) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	_ = json.NewEncoder(w).Encode(payload)
+}