Go HTTP control server with restart openvpn route

- Fix #147
- Dockerfile updated
- Documentation updated
- Using contexts to restart openvpn
- Code foundation for more http routes

internal/server/server.go

@@ -0,0 +1,93 @@
+package server
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"sync"
+	"time"
+
+	"github.com/qdm12/golibs/logging"
+)
+
+type Server interface {
+	SetOpenVPNRestart(f func())
+	Run(ctx context.Context) error
+}
+
+type server struct {
+	address        string
+	logger         logging.Logger
+	restartOpenvpn func()
+	sync.RWMutex
+}
+
+func New(address string, logger logging.Logger) Server {
+	return &server{
+		address: address,
+		logger:  logger.WithPrefix("http server: "),
+	}
+}
+
+func (s *server) Run(ctx context.Context) error {
+	if s.restartOpenvpn == nil {
+		s.logger.Warn("restartOpenvpn function is not set")
+	}
+	server := http.Server{Addr: s.address, Handler: s.makeHandler()}
+	go func() {
+		<-ctx.Done()
+		shutdownCtx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
+		defer cancel()
+		if err := server.Shutdown(shutdownCtx); err != nil {
+			s.logger.Error("failed shutting down: %s", err)
+		}
+	}()
+	s.logger.Info("listening on %s", s.address)
+	return server.ListenAndServe()
+}
+
+func (s *server) SetOpenVPNRestart(f func()) {
+	s.Lock()
+	defer s.Unlock()
+	s.restartOpenvpn = f
+}
+
+func (s *server) makeHandler() http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		s.logger.Info("HTTP %s %s", r.Method, r.RequestURI)
+		switch r.Method {
+		case http.MethodGet:
+			switch r.RequestURI {
+			case "/openvpn/actions/restart":
+				s.RLock()
+				defer s.RUnlock()
+				if s.restartOpenvpn == nil {
+					functionNotSet("restartOpenvpn", s.logger, w)
+					return
+				}
+				s.restartOpenvpn()
+			default:
+				routeDoesNotExist(s.logger, w, r)
+			}
+		default:
+			routeDoesNotExist(s.logger, w, r)
+		}
+	}
+}
+
+func routeDoesNotExist(logger logging.Logger, w http.ResponseWriter, r *http.Request) {
+	w.WriteHeader(http.StatusBadRequest)
+	_, err := w.Write([]byte(fmt.Sprintf("Nothing here for %s %s", r.Method, r.RequestURI)))
+	if err != nil {
+		logger.Error(err)
+	}
+}
+
+func functionNotSet(functionName string, logger logging.Logger, w http.ResponseWriter) {
+	logger.Error("function %s is not set", functionName)
+	w.WriteHeader(http.StatusInternalServerError)
+	_, err := w.Write([]byte(fmt.Sprintf("%s function is not set", functionName)))
+	if err != nil {
+		logger.Error(err)
+	}
+}