Add option to start the recording directly.

Resolves #2.

Author: blueimp

README.md

@@ -1,28 +1,30 @@
 # MJPEG Server
+
 MJPEG Server implements
 [MJPEG over HTTP](https://en.wikipedia.org/wiki/Motion_JPEG#M-JPEG_over_HTTP)
-using [FFmpeg](https://ffmpeg.org/) or any other input source capable of
-piping a multipart JPEG stream to stdout.
+using [FFmpeg](https://ffmpeg.org/) or any other input source capable of piping
+a multipart JPEG stream to stdout.
 
 Its primary use case is providing screen recordings for remote Webdriver tests,
 e.g. for [blueimp/wdio](https://github.com/blueimp/wdio).
 
-It is resource efficient and only starts the screen recording process if there
-is at least one HTTP client connected to the server, stopping the recording when
-there are no more open client connections.
+It is resource efficient and by default only starts the screen recording process
+if there is at least one HTTP client connected to the server, stopping the
+recording when there are no more open client connections.
 
 - [Installation](#installation)
 - [Usage](#usage)
-  * [Options](#options)
-  * [Screencast](#screencast)
-    + [Linux](#linux)
-    + [MacOS](#macos)
-    + [Windows](#windows)
+  - [Options](#options)
+  - [Screencast](#screencast)
+    - [Linux](#linux)
+    - [MacOS](#macos)
+    - [Windows](#windows)
 - [License](#license)
 - [Attributions](#attributions)
 - [Author](#author)
 
 ## Installation
+
 The MJPEG Server binary can be downloaded for Linux, MacOS and Windows from the
 [releases](https://github.com/blueimp/mjpeg-server/releases) page or built from
 source via [go get](https://golang.org/cmd/go/):
@@ -35,6 +37,7 @@ The screencast examples also require [FFmpeg](https://ffmpeg.org/) to be
 installed.
 
 ## Usage
+
 By default, `mjpeg-server` listens on port `9000` on all interfaces and starts
 the given recording command when the first HTTP client connects:
 
@@ -67,6 +70,7 @@ go run main.go -a 127.0.0.1:9000 -- go run mpjpeg/main.go -- gopher.jpg
 It simply streams the provided JPEG images in an endless loop.
 
 ### Options
+
 Available MJPEG Server options can be listed the following way:
 
 ```sh
@@ -79,18 +83,24 @@ Usage of mjpeg-server:
     	TCP listen address (default ":9000")
   -b string
     	Multipart boundary (default "ffmpeg")
+  -d	Start command directly
   -p string
     	URL path (default "/")
   -v	Output version and exit
 ```
 
+The `-d` option starts the given recording command directly on initialization of
+the MJPEG server and keeps it running independently of the number of connected
+HTTP clients, until the MJPEG server process is stopped.
+
 ### Screencast
 
 #### Linux
+
 Start `mjpeg-server` using the
-[x11grab](https://www.ffmpeg.org/ffmpeg-devices.html#x11grab) device,
-selecting the X11 display via `-i :DISPLAY` and the matching screen resolution
-via `-video_size WIDTHxHEIGHT` option:
+[x11grab](https://www.ffmpeg.org/ffmpeg-devices.html#x11grab) device, selecting
+the X11 display via `-i :DISPLAY` and the matching screen resolution via
+`-video_size WIDTHxHEIGHT` option:
 
 ```sh
 mjpeg-server -- ffmpeg \
@@ -108,10 +118,12 @@ mjpeg-server -- ffmpeg \
   -
 ```
 
-#### MacOS 
+#### MacOS
+
 List the available
-[avfoundation](https://www.ffmpeg.org/ffmpeg-devices.html#avfoundation)
-input devices:
+[avfoundation](https://www.ffmpeg.org/ffmpeg-devices.html#avfoundation) input
+devices:
+
 ```sh
 ffmpeg -f avfoundation -list_devices true -i -
 ```
@@ -136,9 +148,10 @@ mjpeg-server -- ffmpeg \
 ```
 
 #### Windows
+
 On Windows, we can use the built-in
-[gdigrab](https://ffmpeg.org/ffmpeg-devices.html#gdigrab)
-input device to capture the whole desktop.
+[gdigrab](https://ffmpeg.org/ffmpeg-devices.html#gdigrab) input device to
+capture the whole desktop.
 
 Start `MJPEGServer` using the following command in a Powershell console:
 
@@ -158,9 +171,11 @@ MJPEGServer -- ffmpeg `
 ```
 
 ## License
+
 Released under the [MIT license](https://opensource.org/licenses/MIT).
 
 ## Attributions
+
 The [Gopher](gopher.jpg) image used for the tests was designed by
 [Renee French](https://reneefrench.blogspot.com/).  
 The design is licensed under the
@@ -169,4 +184,5 @@ The design is licensed under the
 ![Gopher](gopher.jpg)
 
 ## Author
+
 [Sebastian Tschan](https://blueimp.net/)

internal/registry/registry.go

@@ -28,6 +28,7 @@ type logEntry struct {
 type registry struct {
 	command       string
 	args          []string
+	directStart   bool
 	clients       multi.MapWriter
 	counter       uint64
 	stopRecording context.CancelFunc
@@ -54,6 +55,14 @@ func log(id string, registered bool, numClients int) {
 	fmt.Println(string(b))
 }
 
+func (t *registry) startRecording() {
+	t.stopRecording, t.waitForStop = startRecording(
+		t.command,
+		t.args,
+		t.clients,
+	)
+}
+
 // GenerateID returns an auto-incrementing ID.
 func (t *registry) GenerateID() string {
 	return strconv.FormatUint(atomic.AddUint64(&t.counter, 1), 10)
@@ -63,13 +72,9 @@ func (t *registry) GenerateID() string {
 // It returns the new number of clients in the Registry.
 func (t *registry) Add(id string, w io.Writer) (num int) {
 	num = t.clients.Add(w)
-	if num == 1 {
+	if num == 1 && !t.directStart {
 		// First client added, start the recording.
-		t.stopRecording, t.waitForStop = startRecording(
-			t.command,
-			t.args,
-			t.clients,
-		)
+		t.startRecording()
 	}
 	log(id, true, num)
 	return
@@ -79,7 +84,7 @@ func (t *registry) Add(id string, w io.Writer) (num int) {
 // It returns the new number of clients in the Registry.
 func (t *registry) Remove(id string, w io.Writer) (num int) {
 	num = t.clients.Remove(w)
-	if num == 0 {
+	if num == 0 && !t.directStart {
 		// Last client removed, stop the recording.
 		t.stopRecording()
 	}
@@ -88,13 +93,18 @@ func (t *registry) Remove(id string, w io.Writer) (num int) {
 }
 
 // New creates a new Registry.
-func New(command string, args []string) Registry {
-	return &registry{
+func New(command string, args []string, directStart bool) Registry {
+	reg := &registry{
 		command,
 		args,
+		directStart,
 		multi.NewMapWriter(),
 		0,
 		nil,
 		nil,
 	}
+	if directStart {
+		reg.startRecording()
+	}
+	return reg
 }

internal/registry/registry_test.go

@@ -46,7 +46,7 @@ func outputHelper(fn func()) (stdout []byte, stderr []byte) {
 }
 
 func TestNew(t *testing.T) {
-	reg := New("go", []string{"version"})
+	reg := New("go", []string{"version"}, false)
 	if reg == nil {
 		t.Error("Unexpected: nil")
 	}
@@ -57,7 +57,7 @@ func TestNew(t *testing.T) {
 }
 
 func TestGenerateID(t *testing.T) {
-	reg := New("go", []string{"version"})
+	reg := New("go", []string{"version"}, false)
 	id := reg.GenerateID()
 	if id != "1" {
 		t.Errorf("Unexpected generated ID: %s. Expected: %s", id, "1")
@@ -76,7 +76,7 @@ func TestAdd(t *testing.T) {
 	started = 0
 	stopped = 0
 	startRecording = startRecordingHelper
-	reg := New("go", []string{"version"})
+	reg := New("go", []string{"version"}, false)
 	if started != 0 {
 		t.Errorf("Unexpected started recordings: %d. Expected: %d", started, 0)
 	}
@@ -150,7 +150,7 @@ func TestRemove(t *testing.T) {
 	started = 0
 	stopped = 0
 	startRecording = startRecordingHelper
-	reg := New("go", []string{"version"})
+	reg := New("go", []string{"version"}, false)
 	var (
 		buffer1 bytes.Buffer
 		buffer2 bytes.Buffer
@@ -227,3 +227,26 @@ func TestRemove(t *testing.T) {
 		)
 	}
 }
+
+func TestNewWithDirectStart(t *testing.T) {
+	started = 0
+	stopped = 0
+	startRecording = startRecordingHelper
+	reg := New("go", []string{"version"}, true)
+	if started != 1 {
+		t.Errorf("Unexpected started recordings: %d. Expected: %d", started, 1)
+	}
+	var buffer1 bytes.Buffer
+	outputHelper(func() {
+		reg.Add("1", &buffer1)
+	})
+	if started != 1 {
+		t.Errorf("Unexpected started recordings: %d. Expected: %d", started, 1)
+	}
+	outputHelper(func() {
+		reg.Remove("1", &buffer1)
+	})
+	if stopped != 0 {
+		t.Errorf("Unexpected stopped recordings: %d. Expected: %d", stopped, 0)
+	}
+}

main.go

@@ -14,14 +14,15 @@ import (
 var (
 	// Version provides the program version information.
 	// It is provided at build time via -ldflags="-X main.Version=VERSION".
-	Version        = "dev"
-	showVersion    = flag.Bool("v", false, "Output version and exit")
-	addr           = flag.String("a", ":9000", "TCP listen address")
-	urlPath        = flag.String("p", "/", "URL path")
-	boundary       = flag.String("b", "ffmpeg", "Multipart boundary")
-	command        string
-	args           []string
-	reg            registry.Registry
+	Version     = "dev"
+	showVersion = flag.Bool("v", false, "Output version and exit")
+	directStart = flag.Bool("d", false, "Start command directly")
+	addr        = flag.String("a", ":9000", "TCP listen address")
+	urlPath     = flag.String("p", "/", "URL path")
+	boundary    = flag.String("b", "ffmpeg", "Multipart boundary")
+	command     string
+	args        []string
+	reg         registry.Registry
 )
 
 func setHeaders(header http.Header) {
@@ -76,6 +77,6 @@ func main() {
 		fmt.Println(Version)
 		os.Exit(0)
 	}
-	reg = registry.New(command, args)
+	reg = registry.New(command, args, *directStart)
 	log.Fatalln(http.ListenAndServe(*addr, http.HandlerFunc(requestHandler)))
 }

main_internal_test.go

@@ -11,7 +11,7 @@ import (
 )
 
 func TestRequestHandler(t *testing.T) {
-	reg = registry.New(command, args)
+	reg = registry.New(command, args, false)
 	rec := httptest.NewRecorder()
 	ctx, cancel := context.WithCancel(context.Background())
 	req := httptest.NewRequest(
@@ -61,7 +61,7 @@ func TestRequestHandler(t *testing.T) {
 }
 
 func TestRequestHandlerWithInvalidMethod(t *testing.T) {
-	reg = registry.New(command, args)
+	reg = registry.New(command, args, false)
 	rec := httptest.NewRecorder()
 	req := httptest.NewRequest(
 		"POST",
@@ -79,7 +79,7 @@ func TestRequestHandlerWithInvalidMethod(t *testing.T) {
 }
 
 func TestRequestHandlerWithInvalidPath(t *testing.T) {
-	reg = registry.New(command, args)
+	reg = registry.New(command, args, false)
 	rec := httptest.NewRecorder()
 	req := httptest.NewRequest(
 		"GET",
@@ -97,7 +97,7 @@ func TestRequestHandlerWithInvalidPath(t *testing.T) {
 }
 
 func TestRequestHandlerWithCustomPath(t *testing.T) {
-	reg = registry.New(command, args)
+	reg = registry.New(command, args, false)
 	*urlPath = "/banana"
 	rec := httptest.NewRecorder()
 	ctx, cancel := context.WithCancel(context.Background())
@@ -136,7 +136,7 @@ func TestRequestHandlerWithCustomPath(t *testing.T) {
 }
 
 func TestRequestHandlerWithCustomBoundary(t *testing.T) {
-	reg = registry.New(command, args)
+	reg = registry.New(command, args, false)
 	*boundary = "banana"
 	rec := httptest.NewRecorder()
 	ctx, cancel := context.WithCancel(context.Background())