limit file encoding to a single file at a time

go.mod

@@ -4,6 +4,7 @@ go 1.20
 
 require (
 	git.milar.in/milarin/adverr v1.1.0
+	git.milar.in/milarin/channel v0.0.16
 	git.milar.in/milarin/envvars/v2 v2.0.0
 	git.milar.in/milarin/slices v0.0.6
 	github.com/gorilla/mux v1.8.0

go.sum

@@ -1,5 +1,7 @@
 git.milar.in/milarin/adverr v1.1.0 h1:jD9WnOvs40lfMhvqQ7cllOaRJNBMWr1f07/s9jAadp0=
 git.milar.in/milarin/adverr v1.1.0/go.mod h1:joU9sBb7ySyNv4SpTXB0Z4o1mjXsArBw4N27wjgzj9E=
+git.milar.in/milarin/channel v0.0.16 h1:gyxwUFdw2pJUusdNhgnuTb2Tmb5MQAbTYcyxa3wp494=
+git.milar.in/milarin/channel v0.0.16/go.mod h1:We83LTI8S7u7II3pD+A2ChCDWJfCkcBUCUqii9HjTtM=
 git.milar.in/milarin/envvars/v2 v2.0.0 h1:DWRQCWaHqzDD8NGpSgv5tYLuF9A/dVFPAtTvz3oiIqE=
 git.milar.in/milarin/envvars/v2 v2.0.0/go.mod h1:HkdEi+gG2lJSmVq547bTlQV4qQ0hO333bE8IrE0B9yY=
 git.milar.in/milarin/slices v0.0.6 h1:AQoSarZ58WHYol9c6woWJSe8wFpPC2RC4cvIlZpfg9s=

main.go

@@ -193,12 +193,7 @@ func GetEncodeFileHandler(w http.ResponseWriter, r *http.Request) {
 
 	fmt.Printf("encode file to %s: '%s' -> '%s'\n", format, inputFilePath, outputFilePath)
 
-	cmd := exec.Command("ffmpeg", "-i", inputFilePath, "-vn", outputFilePath)
+	if err := EncodeVideo2Mp3(inputFilePath, outputFilePath); err != nil {
-	if err := cmd.Start(); err != nil {
-		InternalServerError(w, err)
-		return
-	}
-	if err := cmd.Wait(); err != nil {
 		InternalServerError(w, err)
 		return
 	}

video_encoder.go

@@ -0,0 +1,33 @@
+package main
+
+import (
+	"os/exec"
+	"sync"
+
+	"git.milar.in/milarin/channel"
+)
+
+var EncodeRunner = channel.NewLimitedRunner(1)
+
+func EncodeVideo2Mp3(inputFile, outputFile string) error {
+	var err error
+
+	wg := &sync.WaitGroup{}
+
+	wg.Add(1)
+	EncodeRunner.Run(func() {
+		defer wg.Done()
+
+		cmd := exec.Command("ffmpeg", "-i", inputFile, "-vn", outputFile)
+		if err = cmd.Start(); err != nil {
+			return
+		}
+
+		if err = cmd.Wait(); err != nil {
+			return
+		}
+	})
+
+	wg.Wait()
+	return err
+}