feat: edge gateway service

gateway/internal/adminapi/server.go

@@ -0,0 +1,133 @@
+// Package adminapi exposes the optional private admin HTTP listener used for
+// operational endpoints such as Prometheus metrics.
+package adminapi
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net"
+	"net/http"
+	"sync"
+
+	"galaxy/gateway/internal/config"
+
+	"go.uber.org/zap"
+)
+
+// Server owns the optional admin HTTP listener exposed by the gateway.
+type Server struct {
+	cfg     config.AdminHTTPConfig
+	handler http.Handler
+	logger  *zap.Logger
+
+	stateMu  sync.RWMutex
+	server   *http.Server
+	listener net.Listener
+}
+
+// NewServer constructs an admin HTTP server for cfg and handler.
+func NewServer(cfg config.AdminHTTPConfig, handler http.Handler, logger *zap.Logger) *Server {
+	if handler == nil {
+		handler = http.NotFoundHandler()
+	}
+	if logger == nil {
+		logger = zap.NewNop()
+	}
+
+	return &Server{
+		cfg:     cfg,
+		handler: handler,
+		logger:  logger.Named("admin_http"),
+	}
+}
+
+// Enabled reports whether the admin listener should run.
+func (s *Server) Enabled() bool {
+	return s != nil && s.cfg.Addr != ""
+}
+
+// Run binds the configured listener and serves the admin HTTP surface until
+// Shutdown closes the server. A disabled admin server returns when ctx is
+// canceled.
+func (s *Server) Run(ctx context.Context) error {
+	if ctx == nil {
+		return errors.New("run admin HTTP server: nil context")
+	}
+	if err := ctx.Err(); err != nil {
+		return err
+	}
+	if !s.Enabled() {
+		<-ctx.Done()
+		return nil
+	}
+
+	listener, err := net.Listen("tcp", s.cfg.Addr)
+	if err != nil {
+		return fmt.Errorf("run admin HTTP server: listen on %q: %w", s.cfg.Addr, err)
+	}
+
+	server := &http.Server{
+		Handler:           s.handler,
+		ReadHeaderTimeout: s.cfg.ReadHeaderTimeout,
+		ReadTimeout:       s.cfg.ReadTimeout,
+		IdleTimeout:       s.cfg.IdleTimeout,
+	}
+
+	s.stateMu.Lock()
+	s.server = server
+	s.listener = listener
+	s.stateMu.Unlock()
+
+	s.logger.Info("admin HTTP server started", zap.String("addr", listener.Addr().String()))
+
+	defer func() {
+		s.stateMu.Lock()
+		s.server = nil
+		s.listener = nil
+		s.stateMu.Unlock()
+	}()
+
+	err = server.Serve(listener)
+	switch {
+	case err == nil:
+		return nil
+	case errors.Is(err, http.ErrServerClosed):
+		s.logger.Info("admin HTTP server stopped")
+		return nil
+	default:
+		return fmt.Errorf("run admin HTTP server: serve on %q: %w", s.cfg.Addr, err)
+	}
+}
+
+// Shutdown gracefully stops the admin HTTP server within ctx.
+func (s *Server) Shutdown(ctx context.Context) error {
+	if ctx == nil {
+		return errors.New("shutdown admin HTTP server: nil context")
+	}
+
+	s.stateMu.RLock()
+	server := s.server
+	s.stateMu.RUnlock()
+
+	if server == nil {
+		return nil
+	}
+
+	if err := server.Shutdown(ctx); err != nil && !errors.Is(err, http.ErrServerClosed) {
+		return fmt.Errorf("shutdown admin HTTP server: %w", err)
+	}
+
+	return nil
+}
+
+func (s *Server) listenAddr() string {
+	s.stateMu.RLock()
+	defer s.stateMu.RUnlock()
+
+	if s.listener == nil {
+		return ""
+	}
+
+	return s.listener.Addr().String()
+}