Making more configurable. Gracefully handle non-existing socket

README.md

@@ -21,7 +21,7 @@ Currently supported features:
 ### With a renderd backend
 
 * Currently there are no prebuilt binaries included here, so you need to build from source (`go build .`)
-* go_tile is hardcoded to use `/var/run/renderd/renderd.sock` right now
+* You need to have a working renderd setup
 
 ### With prerendered Tiles
 
@@ -36,11 +36,15 @@ Now you can view your map at <http://localhost:8080/>. Tiles are served at <http
 If you prefer to run the binary directly you have the following options:
 
 ```
-Usage of /tmp/go-build004735986/b001/exe/osm-tileserver:
+Usage of /tmp/go-build2340306719/b001/exe/osm-tileserver:
   -data string
         Path to directory containing tiles (default "./data")
   -port string
         Listening port (default ":8080")
+  -renderd-timeout int
+        time in seconds to wait for renderd before returning an error to the client. Set negative to disable (default 60)
+  -socket string
+        Path to renderd socket. Set to '' to disable rendering (default "/var/run/renderd/renderd.sock")
   -static string
         Path to static file directory (default "./static/")
 ```

main.go

@@ -123,7 +123,7 @@ func parsePath(path string) (z, x, y uint32, err error) {
 	return
 }
 
-func handleRequest(resp http.ResponseWriter, req *http.Request, data_dir *string) {
+func handleRequest(resp http.ResponseWriter, req *http.Request, data_dir *string, renderd_sock_path string, renderd_timeout time.Duration) {
 	z, x, y, err := parsePath(req.URL.Path)
 	if err != nil {
 		resp.WriteHeader(http.StatusBadRequest)
@@ -135,7 +135,11 @@ func handleRequest(resp http.ResponseWriter, req *http.Request, data_dir *string
 	fileInfo, statErr := os.Stat(metatile_path)
 	if statErr != nil {
 		if errors.Is(statErr, os.ErrNotExist) {
-			renderErr := requestRender(x, y, z)
+			if len(renderd_sock_path) == 0 {
+				resp.WriteHeader(http.StatusNotFound)
+				return
+			}
+			renderErr := requestRender(x, y, z, renderd_sock_path, renderd_timeout)
 			if renderErr != nil {
 				fmt.Printf("Could not generate tile for coordinates %d, %d, %d (x,y,z). '%s'\n", x, y, z, renderErr)
 				// Not returning as we are hoping and praying that rendering did nonetheless produce a file
@@ -164,14 +168,17 @@ func main() {
 	listen_port := flag.String("port", ":8080", "Listening port")
 	data_dir := flag.String("data", "./data", "Path to directory containing tiles")
 	static_dir := flag.String("static", "./static/", "Path to static file directory")
+	renderd_sock_path := flag.String("socket", "/var/run/renderd/renderd.sock", "Path to renderd socket. Set to '' to disable rendering")
+	renderd_timeout := flag.Int("renderd-timeout", 60, "time in seconds to wait for renderd before returning an error to the client. Set negative to disable")
+	var renderd_timeout_duration time.Duration = time.Duration(*renderd_timeout) * time.Second
 	flag.Parse()
 	http.HandleFunc("/tile/", func(w http.ResponseWriter, r *http.Request) {
 		if r.Method != "GET" {
 			w.WriteHeader(http.StatusMethodNotAllowed) // TODO return 4xx wrong method
 			w.Write([]byte("Only GET requests allowed"))
 			return
 		}
-		handleRequest(w, r, data_dir)
+		handleRequest(w, r, data_dir, *renderd_sock_path, renderd_timeout_duration)
 	})
 	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
 		http.FileServer(http.Dir(*static_dir)).ServeHTTP(w, r)

renderer.go

@@ -22,13 +22,15 @@ type Request struct {
 	Map         [44]byte
 }
 
-func requestRender(x, y, z uint32) error {
-	c, err := net.Dial("unix", "/var/run/renderd/renderd.sock")
+func requestRender(x, y, z uint32, renderd_sock_path string, renderd_timeout time.Duration) error {
+	c, err := net.Dial("unix", renderd_sock_path)
 	if err != nil {
-		panic(err)
+		return err
 	}
 	defer c.Close()
-	c.SetDeadline(time.Now().Add(30 * time.Second))
+	if renderd_timeout > 0 {
+		c.SetDeadline(time.Now().Add(renderd_timeout))
+	}
 	request := Request{
 		Version:     3,
 		CmdPriority: 5,