Handled graceful restart of server

server/server.go

@@ -0,0 +1,106 @@
+package server
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+
+	"githib.com/Theodor-Springmann-Stiftung/kgpz_web/app"
+)
+
+// INFO: Server is a meta-package that handles the current router, which it starts in a goroutine.
+// The router must be able to restart itself, if the data validation fails, so we subscribe to a channel on the app,
+// which indicates that the data has changed
+// On data change:
+// - we invalidate all caches if data is valid
+// - we reload all clients
+// - if data validity catastrophically fails, we restart the router to map error pages.
+type Server struct {
+	running chan bool
+	alive   chan bool
+	Killed  chan bool
+}
+
+func Start(k *app.KGPZ) *Server {
+	return &Server{}
+}
+
+func (s *Server) Start() {
+	srv := &http.Server{Addr: ":8080"}
+	s.running = make(chan bool, 1)
+	s.alive = make(chan bool, 1)
+	s.Killed = s.killHandler(srv, s.alive)
+	shuttingdown := s.shutdownHandler(srv, s.running)
+	shutdown := s.runnerHandler(srv, shuttingdown)
+	s.restartHandler(shutdown)
+}
+
+func (s *Server) Restart() {
+	s.running <- false
+}
+
+func (s *Server) Kill() {
+	s.alive <- false
+}
+
+func (s *Server) killHandler(srv *http.Server, alive chan bool) chan bool {
+	kill := make(chan bool, 1)
+
+	go func() {
+		<-alive
+
+		if err := srv.Shutdown(nil); err != nil {
+			fmt.Println("Error shutting down server")
+		}
+
+		kill <- true
+	}()
+
+	return kill
+}
+
+func (s *Server) restartHandler(shutdown chan bool) {
+	go func() {
+		<-shutdown
+		s.Start()
+	}()
+}
+
+func (s *Server) runnerHandler(srv *http.Server, shuttingdown chan bool) chan bool {
+	shutdown := make(chan bool, 1)
+
+	go func() {
+		// EXAMPLE:
+		http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+			io.WriteString(w, "hello world\n")
+		})
+
+		if err := srv.ListenAndServe(); err != http.ErrServerClosed {
+			fmt.Println("Error starting server")
+		}
+
+		<-shuttingdown
+		shutdown <- true
+	}()
+
+	return shutdown
+}
+
+func (s *Server) shutdownHandler(srv *http.Server, running chan bool) chan bool {
+	shuttingdown := make(chan bool, 1)
+
+	go func() {
+		<-running
+
+		if err := srv.Shutdown(nil); err != nil {
+			fmt.Println("Error shutting down server")
+		}
+
+		shuttingdown <- true
+	}()
+
+	return shuttingdown
+}
+
+func (s *Server) Shutdown() {
+}