update resizer lock position

Author: totegamma

main.go

@@ -80,17 +80,7 @@ func main() {
 
 	init_resize(512 * 1024 * 1024)
 
-	sem := make(chan struct{}, 1)
-
-	e.GET("/image/*", func(c echo.Context) error {
-		sem <- struct{}{}
-		defer func() {
-			<-sem
-		}()
-
-		return ImageHandler(c)
-	})
-
+	e.GET("/image/*", ImageHandler)
 	e.GET("/summary", SummaryHandler)
 
 	var currentCacheSizeMetrics = prometheus.NewGauge(prometheus.GaugeOpts{

resize.go

@@ -14,8 +14,16 @@ func init_resize(memoryLimit int) {
 	}
 }
 
+var sem = make(chan struct{}, 1)
+
 func resize(input, output string, width, height int) int {
 
+	// limit to one resize operation at a time
+	sem <- struct{}{}
+	defer func() {
+		<-sem
+	}()
+
 	cInput := C.CString(input)
 	defer C.free(unsafe.Pointer(cInput))