add todos for error handling

README.md

@@ -14,7 +14,7 @@ A browser-in-browser "proxy" server that allows to use historical / vintage web
 * Scroll web page by clicking on the in-image scroll bar.
 * WRP also allows **a single tall image without the vertical scrollbar** and use client scrolling. To enable this, simply height **H** to `0` . However this should not be used with old and low spec clients. Such tall images will be very large, take a lot of memory and long time to process, especially for GIFs.
 * Do not use client browser history-back, instead use **Bk** button in the app.
-* You can re-capture page screenshot without reloading by using **St** (Stop).
+* You can re-capture page screenshot without reloading by using **St** (Stop). This is useful if page didn't render fully before screenshot is taken.
 * You can also reload and re-capture current page with **Re** (Reload).
 * To send keystrokes, fill **K** input box and press **Go**. There also are buttons for backspace, enter and arrow keys.
 * Prefer PNG over GIF if your browser supports it. PNG is much faster, whereas GIF requires a lot of additional processing on both client and server to encode/decode.

wrp.go

@@ -18,6 +18,7 @@ import (
 	"image/color/palette"
 	"image/gif"
 	"image/png"
+	"io"
 	"io/ioutil"
 	"log"
 	"math"
@@ -39,18 +40,23 @@ import (
 	"github.com/soniakeys/quant/median"
 )
 
+const version = "4.6.0"
+
 var (
-	version  = "4.6.0"
-	srv      http.Server
-	ctx      context.Context
-	cancel   context.CancelFunc
-	img      = make(map[string]bytes.Buffer)
-	ismap    = make(map[string]wrpReq)
-	noDel    bool
-	defType  string
-	defGeom  geom
-	htmlTmpl *template.Template
-	delay    time.Duration
+	addr        = flag.String("l", ":8080", "Listen address:port, default :8080")
+	headless    = flag.Bool("h", true, "Headless mode / hide browser window (default true)")
+	noDel       = flag.Bool("n", false, "Do not free maps and images after use")
+	defType     = flag.String("t", "gif", "Image type: gif|png")
+	fgeom       = flag.String("g", "1152x600x216", "Geometry: width x height x colors, height can be 0 for unlimited")
+	htmFnam     = flag.String("ui", "wrp.html", "HTML template file for the UI")
+	delay       = flag.Duration("s", 2*time.Second, "Delay/sleep after page is rendered and before screenshot is taken")
+	srv         http.Server
+	actx, ctx   context.Context
+	acncl, cncl context.CancelFunc
+	img         = make(map[string]bytes.Buffer)
+	ismap       = make(map[string]wrpReq)
+	defGeom     geom
+	htmlTmpl    *template.Template
 )
 
 //go:embed *.html
@@ -132,7 +138,7 @@ func (rq *wrpReq) parseForm() {
 	rq.buttons = rq.r.FormValue("Fn")
 	rq.imgType = rq.r.FormValue("t")
 	if rq.imgType != "gif" && rq.imgType != "png" {
-		rq.imgType = defType
+		rq.imgType = *defType
 	}
 	log.Printf("%s WrpReq from UI Form: %+v\n", rq.r.RemoteAddr, rq)
 }
@@ -206,19 +212,26 @@ func (rq *wrpReq) action() chromedp.Action {
 	return chromedp.Navigate(rq.url)
 }
 
-// Process Keyboard and Mouse events or Navigate to the desired URL.
+// Navigate to the desired URL.
 func (rq *wrpReq) navigate() {
-	err := chromedp.Run(ctx, rq.action())
-	if err != nil {
-		if err.Error() == "context canceled" {
-			log.Printf("%s Contex cancelled, try again", rq.r.RemoteAddr)
-			fmt.Fprintf(rq.w, "<BR>%s<BR> -- restarting, try again", err)
-			ctx, cancel = chromedp.NewContext(context.Background())
-			return
-		}
-		log.Printf("%s %s", rq.r.RemoteAddr, err)
-		fmt.Fprintf(rq.w, "<BR>%s<BR>", err)
+	ctxErr(chromedp.Run(ctx, rq.action()), rq.w)
+}
+
+// Handle context errors
+func ctxErr(err error, w io.Writer) {
+	// TODO: callers should have retry logic, perhaps create another function
+	// that takes ...chromedp.Action and retries with give up
+	if err == nil {
+		return
 	}
+	log.Printf("Context error: %s", err)
+	fmt.Fprintf(w, "Context error: %s<BR>\n", err)
+	if err.Error() != "context canceled" {
+		return
+	}
+	ctx, cncl = chromedp.NewContext(actx)
+	log.Printf("Created new context, try again")
+	fmt.Fprintln(w, "Created new context, try again")
 }
 
 // https://github.com/chromedp/chromedp/issues/979
@@ -278,7 +291,6 @@ func gifPalette(i image.Image, n int64) image.Image {
 
 // Capture currently rendered web page to an image and fake ISMAP
 func (rq *wrpReq) capture() {
-	var err error
 	var styles []*css.ComputedStyleProperty
 	var r, g, b int
 	var h int64
@@ -307,21 +319,10 @@ func (rq *wrpReq) capture() {
 	}
 	chromedp.Run(
 		ctx, emulation.SetDeviceMetricsOverride(int64(float64(rq.width)/rq.zoom), height, rq.zoom, false),
-		chromedp.Sleep(delay), // TODO(tenox): find a better way to determine if page is rendered
+		chromedp.Sleep(*delay), // TODO(tenox): find a better way to determine if page is rendered
 	)
 	// Capture screenshot...
-	err = chromedp.Run(ctx, chromedpCaptureScreenshot(&pngcap, rq.height))
-	if err != nil {
-		if err.Error() == "context canceled" {
-			log.Printf("%s Contex cancelled, try again", rq.r.RemoteAddr)
-			fmt.Fprintf(rq.w, "<BR>%s<BR> -- restarting, try again", err)
-			ctx, cancel = chromedp.NewContext(context.Background())
-			return
-		}
-		log.Printf("%s Failed to capture screenshot: %s\n", rq.r.RemoteAddr, err)
-		fmt.Fprintf(rq.w, "<BR>Unable to capture screenshot:<BR>%s<BR>\n", err)
-		return
-	}
+	ctxErr(chromedp.Run(ctx, chromedpCaptureScreenshot(&pngcap, rq.height)), rq.w)
 	seq := rand.Intn(9999)
 	imgpath := fmt.Sprintf("/img/%04d.%s", seq, rq.imgType)
 	mappath := fmt.Sprintf("/map/%04d.map", seq)
@@ -382,7 +383,7 @@ func pageServer(w http.ResponseWriter, r *http.Request) {
 		rq.printHTML(printParams{bgColor: "#FFFFFF"})
 		return
 	}
-	rq.navigate()
+	rq.navigate() // TODO: if error from navigate do not capture
 	rq.capture()
 }
 
@@ -397,7 +398,7 @@ func mapServer(w http.ResponseWriter, r *http.Request) {
 		log.Printf("Unable to find map %s\n", r.URL.Path)
 		return
 	}
-	if !noDel {
+	if !*noDel {
 		defer delete(ismap, r.URL.Path)
 	}
 	n, err := fmt.Sscanf(r.URL.RawQuery, "%d,%d", &rq.mouseX, &rq.mouseY)
@@ -411,7 +412,7 @@ func mapServer(w http.ResponseWriter, r *http.Request) {
 		rq.printHTML(printParams{bgColor: "#FFFFFF"})
 		return
 	}
-	rq.navigate()
+	rq.navigate() // TODO: if error from navigate do not capture
 	rq.capture()
 }
 
@@ -424,7 +425,7 @@ func imgServer(w http.ResponseWriter, r *http.Request) {
 		log.Printf("%s Unable to find image %s\n", r.RemoteAddr, r.URL.Path)
 		return
 	}
-	if !noDel {
+	if !*noDel {
 		defer delete(img, r.URL.Path)
 	}
 	switch {
@@ -451,7 +452,8 @@ func haltServer(w http.ResponseWriter, r *http.Request) {
 	fmt.Fprintf(w, "Shutting down WRP...\n")
 	w.(http.Flusher).Flush()
 	time.Sleep(time.Second * 2)
-	cancel()
+	cncl()
+	acncl()
 	srv.Shutdown(context.Background())
 	os.Exit(1)
 }
@@ -463,11 +465,13 @@ func tmpl(t string) string {
 	if err != nil {
 		goto builtin
 	}
+	defer fh.Close()
+
 	tmpl, err = ioutil.ReadAll(fh)
 	if err != nil {
 		goto builtin
 	}
-	log.Printf("Got UI template from %v file\n", t)
+	log.Printf("Got HTML UI template from %v file, size %v \n", t, len(tmpl))
 	return string(tmpl)
 
 builtin:
@@ -475,51 +479,36 @@ builtin:
 	if err != nil {
 		log.Fatal(err)
 	}
+	defer fhs.Close()
 
 	tmpl, err = ioutil.ReadAll(fhs)
 	if err != nil {
 		log.Fatal(err)
 	}
-	log.Printf("Got UI template from built-in\n")
+	log.Printf("Got HTML UI template from embed\n")
 	return string(tmpl)
 }
 
 // Main...
 func main() {
-	var addr, fgeom, tHTML string
-	var headless bool
-	var debug bool
 	var err error
-	flag.StringVar(&addr, "l", ":8080", "Listen address:port, default :8080")
-	flag.BoolVar(&headless, "h", true, "Headless mode - hide browser window")
-	flag.BoolVar(&debug, "d", false, "Debug ChromeDP")
-	flag.BoolVar(&noDel, "n", false, "Do not free maps and images after use")
-	flag.StringVar(&defType, "t", "gif", "Image type: gif|png")
-	flag.StringVar(&fgeom, "g", "1152x600x216", "Geometry: width x height x colors, height can be 0 for unlimited")
-	flag.StringVar(&tHTML, "ui", "wrp.html", "HTML template file for the UI")
-	flag.DurationVar(&delay, "s", 2*time.Second, "Delay/sleep after page is rendered and before screenshot is taken")
 	flag.Parse()
 	if len(os.Getenv("PORT")) > 0 {
-		addr = ":" + os.Getenv(("PORT"))
+		*addr = ":" + os.Getenv(("PORT"))
 	}
-	n, err := fmt.Sscanf(fgeom, "%dx%dx%d", &defGeom.w, &defGeom.h, &defGeom.c)
+	n, err := fmt.Sscanf(*fgeom, "%dx%dx%d", &defGeom.w, &defGeom.h, &defGeom.c)
 	if err != nil || n != 3 {
 		log.Fatalf("Unable to parse -g geometry flag / %s", err)
 	}
 
 	opts := append(chromedp.DefaultExecAllocatorOptions[:],
-		chromedp.Flag("headless", headless),
+		chromedp.Flag("headless", *headless),
 		chromedp.Flag("hide-scrollbars", false),
 	)
-	actx, acancel := chromedp.NewExecAllocator(context.Background(), opts...)
-	defer acancel()
-	switch debug {
-	case true:
-		ctx, cancel = chromedp.NewContext(actx, chromedp.WithDebugf(log.Printf))
-	default:
-		ctx, cancel = chromedp.NewContext(actx)
-	}
-	defer cancel()
+	actx, acncl = chromedp.NewExecAllocator(context.Background(), opts...)
+	defer acncl()
+	ctx, cncl = chromedp.NewContext(actx)
+	defer cncl()
 
 	rand.Seed(time.Now().UnixNano())
 
@@ -528,7 +517,8 @@ func main() {
 	go func() {
 		<-c
 		log.Printf("Interrupt - shutting down.")
-		cancel()
+		cncl()
+		acncl()
 		srv.Shutdown(context.Background())
 		os.Exit(1)
 	}()
@@ -541,15 +531,15 @@ func main() {
 
 	log.Printf("Web Rendering Proxy Version %s\n", version)
 	log.Printf("Args: %q", os.Args)
-	log.Printf("Default Img Type: %v, Geometry: %+v", defType, defGeom)
+	log.Printf("Default Img Type: %v, Geometry: %+v", *defType, defGeom)
 
-	htmlTmpl, err = template.New("wrp.html").Parse(tmpl(tHTML))
+	htmlTmpl, err = template.New("wrp.html").Parse(tmpl(*htmFnam))
 	if err != nil {
 		log.Fatal(err)
 	}
 
-	log.Printf("Starting WRP http server on %s\n", addr)
-	srv.Addr = addr
+	log.Printf("Starting WRP http server on %s\n", *addr)
+	srv.Addr = *addr
 	err = srv.ListenAndServe()
 	if err != nil {
 		log.Fatal(err)