refactor clean exit code

so much work just to let cleanup run & to pause fluting :(

main.go

@@ -9,7 +9,6 @@ import (
 	"os/signal"
 	"runtime/pprof"
 	"sync"
-	"time"
 
 	"github.com/SpeckiJ/Hochwasser/pixelflut"
 	"github.com/SpeckiJ/Hochwasser/rpc"
@@ -22,7 +21,6 @@ var x = flag.Int("x", 0, "Offset of posted image from left border")
 var y = flag.Int("y", 0, "Offset of posted image from top border")
 var connections = flag.Int("connections", 4, "Number of simultaneous connections. Each connection posts a subimage")
 var address = flag.String("host", "127.0.0.1:1337", "Server address")
-var runtime = flag.String("runtime", "60s", "exit after timeout")
 var shuffle = flag.Bool("shuffle", false, "pixel send ordering")
 var fetchImgPath = flag.String("fetch-image", "", "path to save the fetched pixel state to")
 var ránAddr = flag.String("rán", "", "enable rpc server to distribute jobs, listening on the given address/port")
@@ -42,6 +40,14 @@ func main() {
 		defer pprof.StopCPUProfile()
 	}
 
+	// :cleanExit setup
+	//   stop chan is closed at end of main process, telling async tasks to stop.
+	//   wg waits until async tasks gracefully stopped
+	wg := sync.WaitGroup{}
+	stopChan := make(chan bool)
+	interruptChan := make(chan os.Signal)
+	signal.Notify(interruptChan, os.Interrupt)
+
 	if *imgPath != "" {
 		offset := image.Pt(*x, *y)
 		img := readImage(*imgPath)
@@ -55,21 +61,11 @@ func main() {
 
 		if *ránAddr != "" {
 			// run RPC server, tasking clients to flut
-			r := rpc.SummonRán(*ránAddr)
+			wg.Add(1)
+			r := rpc.SummonRán(*ránAddr, stopChan, &wg)
 			r.SetTask(img, offset, *address, *connections) // @incomplete
-			select {}                                      // block forever
 
 		} else {
-
-			// local 🌊🌊🌊🌊🌊🌊🌊🌊🌊🌊🌊🌊🌊🌊🌊
-			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 != "" {
@@ -78,30 +74,26 @@ func main() {
 				defer writeImage(*fetchImgPath, fetchedImg)
 			}
 
-			// :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())
-			}
-
-			interruptChan := make(chan os.Signal)
-			signal.Notify(interruptChan, os.Interrupt)
-			select {
-			case <-time.After(timer):
-			case <-interruptChan:
-			}
+			// local 🌊🌊🌊🌊🌊🌊🌊🌊🌊🌊🌊🌊🌊🌊🌊
+			wg.Add(1)
+			go pixelflut.Flut(img, offset, *shuffle, *address, *connections, stopChan, &wg)
 		}
 
 	} else if *hevringAddr != "" {
 		// connect to RPC server and execute their tasks
 		rpc.ConnectHevring(*hevringAddr)
-		select {} // block forever
 
 	} else {
 		log.Fatal("must specify -image or -hevring")
 	}
+
+	// :cleanExit logic:
+	//   notify all async tasks to stop on interrupt
+	//   then wait for clean shutdown of all tasks before exiting
+	//   TODO: make this available to all invocation types
+	select {
+	case <-interruptChan:
+	}
+	close(stopChan)
+	wg.Wait()
 }

pixelflut/api.go

@@ -11,9 +11,9 @@ import (
 )
 
 // Flut asynchronously sends the given image to pixelflut server at `address`
-//   using `conns` connections. Pixels are sent row wise, unless `shuffle` is set.
+//   using `conns` connections. Pixels are sent column wise, unless `shuffle`
+//   is set. Stops when stop is closed.
 // @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 {
@@ -27,14 +27,16 @@ func Flut(img image.Image, position image.Point, shuffle bool, address string, c
 		go bombAddress(msg, address, stop, &bombWg)
 	}
 	bombWg.Wait()
+	if wg != nil {
 		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, 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)
@@ -42,18 +44,14 @@ func FetchImage(bounds image.Rectangle, address string, conns int, stop chan boo
 			log.Fatal(err)
 		}
 
-		// @cleanup: parsePixels calls conn.Close(), as deferring it here would
-		//   instantly close it
 		go readPixels(img, conn, stop)
-		// go bombConn(cmds[i], conn, stop)
+		go bombConn(cmds[i], conn, stop)
 	}
 
 	return img
 }
 
 func readPixels(target *image.NRGBA, conn net.Conn, stop chan bool) {
-	defer conn.Close()
-
 	reader := bufio.NewReader(conn)
 	col := make([]byte, 3)
 	for {

pixelflut/net.go

@@ -10,7 +10,7 @@ import (
 //   called as goroutines
 
 // bombAddress writes the given message via plain TCP to the given address,
-// forever, as fast as possible.
+// as fast as possible, until stop is closed.
 func bombAddress(message []byte, address string, stop chan bool, wg *sync.WaitGroup) {
 	conn, err := net.Dial("tcp", address)
 	if err != nil {
@@ -25,7 +25,6 @@ func bombConn(message []byte, conn net.Conn, stop chan bool) {
 	for {
 		select {
 		case <-stop:
-			log.Println("stopChan bombConn")
 			return
 		default:
 			_, err := conn.Write(message)

rpc/dottir.go

@@ -6,7 +6,7 @@ import (
 	"log"
 	"net"
 	"net/rpc"
-	// "sync"
+	"os"
 	"time"
 
 	"github.com/SpeckiJ/Hochwasser/pixelflut"
@@ -50,7 +50,6 @@ 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
 
 	go pixelflut.Flut(task.Img, task.Offset, task.Shuffle, task.Address, task.MaxConns, h.taskQuit, nil)
 	reply.Ok = true
@@ -64,7 +63,6 @@ func (h *Hevring) Status(x int, reply *FlutAck) error {
 }
 
 func (h *Hevring) Stop(x int, reply *FlutAck) error {
-	// @incomplete
 	if (h.task != FlutTask{}) {
 		fmt.Println("[hevring] stopping task")
 		h.task = FlutTask{}
@@ -78,7 +76,8 @@ func (h *Hevring) Stop(x int, reply *FlutAck) error {
 func (h *Hevring) Die(x int, reply *FlutAck) error {
 	go func() { // @cleanup: hacky
 		time.Sleep(100 * time.Millisecond)
-		log.Fatal("[hevring] Rán disconnected, stopping")
+		fmt.Println("[hevring] Rán disconnected, stopping")
+		os.Exit(0)
 	}()
 	reply.Ok = true
 	return nil

rpc/ran.go

@@ -9,8 +9,8 @@ import (
 	"net"
 	"net/rpc"
 	"os"
-	"os/signal"
 	"strings"
+	"sync"
 	"time"
 )
 
@@ -19,7 +19,10 @@ type Rán struct {
 	task    FlutTask
 }
 
-func SummonRán(address string) *Rán {
+// SummonRán sets up the RPC master, accepting connections at addres (":1234")
+// Connects calls methods on each client's rpc provider, killing all clients
+// when stopChan is closed.
+func SummonRán(address string, stopChan chan bool, wg *sync.WaitGroup) *Rán {
 	r := new(Rán)
 
 	l, err := net.Listen("tcp", address)
@@ -58,8 +61,8 @@ func SummonRán(address string) *Rán {
 			var clients []*rpc.Client
 			for _, c := range r.clients {
 				status := FlutAck{}
-				err3 := c.Call("Hevring.Status", 0, &status)
-				if err3 == nil || status.Ok {
+				err := c.Call("Hevring.Status", 0, &status)
+				if err == nil && status.Ok {
 					clients = append(clients, c)
 				}
 			}
@@ -100,21 +103,18 @@ func SummonRán(address string) *Rán {
 
 	// kill clients on exit
 	go func() {
-		sigChan := make(chan os.Signal, 1)
-		signal.Notify(sigChan, os.Interrupt)
-		for {
-			<-sigChan
+		<-stopChan
 		for _, c := range r.clients {
 			ack := FlutAck{}
 			c.Call("Hevring.Die", 0, &ack) // @speed: async
 		}
-			os.Exit(0) // @bug :cleanExit
-		}
+		wg.Done()
 	}()
 
 	return r
 }
 
+// SetTask assigns a FlutTask to Rán, distributing it to all clients
 func (r *Rán) SetTask(img image.Image, offset image.Point, address string, maxConns int) {
 	// @incomplete: smart task creation:
 	//   fetch server state & sample foreign activity in image regions. assign