app.go

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"net/http"
	"os"
	"os/signal"
	"syscall"
	"time"

	"code.fbi.h-da.de/danet/gosdn/application-framework/event"
	"github.com/lesismal/nbio/nbhttp"
	"github.com/sirupsen/logrus"
)

// Application is an example for a sdn application.
type Application struct {
	eventService event.ServiceInterface
	stopChannel  chan os.Signal
}

// Run runs the application.
func (a *Application) Run() error {
	signal.Notify(a.stopChannel, os.Interrupt, syscall.SIGTERM)

	// subscribe to Add,Delete and Update event types.
	a.eventService.SubscribeToEventType([]event.TypeToCallbackTuple{
		{Type: event.Add, Callback: a.callback},
		{Type: event.Delete, Callback: a.callback},
		{Type: event.Update, Callback: a.callback},
	})
	a.eventService.SetupEventReciever(a.stopChannel)

	mux := &http.ServeMux{}
	mux.HandleFunc("/events", onWebsocket)

	svr := nbhttp.NewServer(nbhttp.Config{
		Network: "tcp",
		Addrs:   []string{"localhost:4000"},
		Handler: mux,
	})

	err := svr.Start()
	if err != nil {
		return fmt.Errorf("Server start failed: %w\n", err)
	}

	<-a.stopChannel
	ctx, cancel := context.WithTimeout(context.Background(), time.Second*5)
	defer cancel()
	return svr.Shutdown(ctx)
}

// callback handles an incoming event from the event system. The event is
// turned into JSON encoding and published to all websocket clients through the
// ClientManager.
func (a *Application) callback(event *event.Event) {
	b, err := json.Marshal(event)
	if err != nil {
		logrus.Error("Failed marshal of event")
	}
	clientManager.Publish(b)
}