wip: clean exit

start adding a mechanism for stopping async tasks,
so we can cleanly quit and stop fluting without quitting

main.go

@@ -6,7 +6,9 @@ import (
 	"log"
 	"net"
 	"os"
+	"os/signal"
 	"runtime/pprof"
+	"sync"
 	"time"
 
 	"github.com/SpeckiJ/Hochwasser/pixelflut"
@@ -60,22 +62,38 @@ func main() {
 		} else {
 
 			// local 🌊🌊🌊🌊🌊🌊🌊🌊🌊🌊🌊🌊🌊🌊🌊
-			pixelflut.Flut(img, offset, *shuffle, *address, *connections)
+			var wg sync.WaitGroup
+			defer wg.Wait()
+			stopChan := make(chan bool)
+			defer close(stopChan)
+
+			wg.Add(1) // :cleanExit: is this WG needed? we only have one task running at a time?
+			go pixelflut.Flut(img, offset, *shuffle, *address, *connections, stopChan, &wg)
 
 			// fetch server state and save to file
 			// @incomplete: make this available also when not fluting?
 			if *fetchImgPath != "" {
-				fetchedImg := pixelflut.FetchImage(img.Bounds().Add(offset), *address, 1)
+				fetchedImg := pixelflut.FetchImage(img.Bounds().Add(offset), *address, 1, stopChan)
 				*connections -= 1
 				defer writeImage(*fetchImgPath, fetchedImg)
 			}
 
-			// Terminate after timeout to save resources
+			// :cleanExit logic:
+			//   notify all async tasks to stop on interrupt or after timeout,
+			//   then wait for clean shutdown of all tasks before exiting
+			//   TODO: make this available to all invocation types
+
 			timer, err := time.ParseDuration(*runtime)
 			if err != nil {
 				log.Fatal("Invalid runtime specified: " + err.Error())
 			}
-			time.Sleep(timer)
+
+			interruptChan := make(chan os.Signal)
+			signal.Notify(interruptChan, os.Interrupt)
+			select {
+			case <-time.After(timer):
+			case <-interruptChan:
+			}
 		}
 
 	} else if *hevringAddr != "" {
@@ -87,9 +105,3 @@ func main() {
 		log.Fatal("must specify -image or -hevring")
 	}
 }
-
-/**
- * @incomplete: clean exit
- * to ensure cleanup is done (rpc disconnects, cpuprof, image writing, ...),
- * we should catch signals and force-exit all goroutines (bomb, rpc). via channel?
- */

pixelflut/api.go

@@ -7,27 +7,34 @@ import (
 	"image/color"
 	"log"
 	"net"
+	"sync"
 )
 
 // Flut asynchronously sends the given image to pixelflut server at `address`
 //   using `conns` connections. Pixels are sent row wise, unless `shuffle` is set.
-func Flut(img image.Image, position image.Point, shuffle bool, address string, conns int) {
+// @cleanup: use FlutTask{} as arg
+// @incomplete :cleanExit
+func Flut(img image.Image, position image.Point, shuffle bool, address string, conns int, stop chan bool, wg *sync.WaitGroup) {
 	cmds := commandsFromImage(img, position)
 	if shuffle {
 		cmds.Shuffle()
 	}
-
 	messages := cmds.Chunk(conns)
+
+	bombWg := sync.WaitGroup{}
 	for _, msg := range messages {
-		go bombAddress(msg, address)
+		bombWg.Add(1)
+		go bombAddress(msg, address, stop, &bombWg)
 	}
+	bombWg.Wait()
+	wg.Done()
 }
 
 // FetchImage asynchronously uses `conns` to fetch pixels within `bounds` from
 //   a pixelflut server at `address`, and writes them into the returned Image.
-func FetchImage(bounds image.Rectangle, address string, conns int) (img *image.NRGBA) {
+func FetchImage(bounds image.Rectangle, address string, conns int, stop chan bool) (img *image.NRGBA) {
 	img = image.NewNRGBA(bounds)
-	cmds := cmdsFetchImage(bounds).Chunk(conns)
+	// cmds := cmdsFetchImage(bounds).Chunk(conns)
 
 	for i := 0; i < conns; i++ {
 		conn, err := net.Dial("tcp", address)
@@ -37,19 +44,24 @@ func FetchImage(bounds image.Rectangle, address string, conns int) (img *image.N
 
 		// @cleanup: parsePixels calls conn.Close(), as deferring it here would
 		//   instantly close it
-		go readPixels(img, conn)
-		go bombConn(cmds[i], conn)
+		go readPixels(img, conn, stop)
+		// go bombConn(cmds[i], conn, stop)
 	}
 
 	return img
 }
 
-func readPixels(target *image.NRGBA, conn net.Conn) {
+func readPixels(target *image.NRGBA, conn net.Conn, stop chan bool) {
 	defer conn.Close()
 
 	reader := bufio.NewReader(conn)
 	col := make([]byte, 3)
 	for {
+		select {
+		case <-stop:
+			return
+
+		default:
 			res, err := reader.ReadSlice('\n')
 			if err != nil {
 				log.Fatal(err)
@@ -71,6 +83,7 @@ func readPixels(target *image.NRGBA, conn net.Conn) {
 			target.SetNRGBA(x, y, color.NRGBA{col[0], col[1], col[2], 255})
 		}
 	}
+}
 
 func asciiToInt(buf []byte) (v int) {
 	for _, c := range buf {

pixelflut/net.go

@@ -3,6 +3,7 @@ package pixelflut
 import (
 	"log"
 	"net"
+	"sync"
 )
 
 // @speed: add some performance reporting mechanism on these functions when
@@ -10,21 +11,27 @@ import (
 
 // bombAddress writes the given message via plain TCP to the given address,
 // forever, as fast as possible.
-func bombAddress(message []byte, address string) {
+func bombAddress(message []byte, address string, stop chan bool, wg *sync.WaitGroup) {
 	conn, err := net.Dial("tcp", address)
 	if err != nil {
 		log.Fatal(err)
 	}
 	defer conn.Close()
-
-	bombConn(message, conn)
+	bombConn(message, conn, stop)
+	wg.Done()
 }
 
-func bombConn(message []byte, conn net.Conn) {
+func bombConn(message []byte, conn net.Conn, stop chan bool) {
 	for {
+		select {
+		case <-stop:
+			log.Println("stopChan bombConn")
+			return
+		default:
 			_, err := conn.Write(message)
 			if err != nil {
 				log.Fatal(err)
 			}
 		}
 	}
+}

rpc/dottir.go

@@ -6,6 +6,7 @@ import (
 	"log"
 	"net"
 	"net/rpc"
+	// "sync"
 	"time"
 
 	"github.com/SpeckiJ/Hochwasser/pixelflut"
@@ -25,6 +26,7 @@ func ConnectHevring(ránAddress string) {
 
 type Hevring struct {
 	task     FlutTask
+	taskQuit chan bool
 }
 
 type FlutTask struct {
@@ -47,8 +49,10 @@ func (h *Hevring) Flut(task FlutTask, reply *FlutAck) error {
 
 	fmt.Printf("[hevring] Rán gave us /w o r k/! %v\n", task)
 	h.task = task
+	h.taskQuit = make(chan bool)
 	// @incomplete: async errorhandling
-	pixelflut.Flut(task.Img, task.Offset, task.Shuffle, task.Address, task.MaxConns)
+
+	go pixelflut.Flut(task.Img, task.Offset, task.Shuffle, task.Address, task.MaxConns, h.taskQuit, nil)
 	reply.Ok = true
 	return nil
 }
@@ -64,6 +68,8 @@ func (h *Hevring) Stop(x int, reply *FlutAck) error {
 	if (h.task != FlutTask{}) {
 		fmt.Println("[hevring] stopping task")
 		h.task = FlutTask{}
+		close(h.taskQuit)
+		h.taskQuit = nil
 		reply.Ok = true
 	}
 	return nil