Don't read new frames before the previous frame has been sent.

lib/units/device/plugins/screen/stream.js

@@ -33,7 +33,10 @@ module.exports = syrup.serial()
       this.output = null
       this.socket = null
       this.banner = null
+      this.parser = null
       this.frameConfig = config
+      this.readable = false
+      this.needsReadable = false
     }
 
     util.inherits(FrameProducer, EventEmitter)
@@ -62,13 +65,14 @@ module.exports = syrup.serial()
               return this._connectService()
             })
             .then(function(socket) {
+              this.parser = new FrameParser()
               this.socket = new RiskyStream(socket)
                 .on('unexpectedEnd', this._socketEnded.bind(this))
               return this._readBanner(this.socket.stream)
             })
             .then(function(banner) {
               this.banner = banner
-              return this._readFrames()
+              return this._readFrames(this.socket.stream)
             })
             .then(function() {
               this.runningState = FrameProducer.STATE_STARTED
@@ -107,6 +111,7 @@ module.exports = syrup.serial()
               this.output = null
               this.socket = null
               this.banner = null
+              this.parser = null
               this._ensureState()
             })
         }
@@ -162,6 +167,29 @@ module.exports = syrup.serial()
       this._configChanged()
     }
 
+    FrameProducer.prototype.nextFrame = function() {
+      var frame = null, chunk
+
+      if (this.parser) {
+        while ((frame = this.parser.nextFrame()) === null) {
+          if ((chunk = this.socket.stream.read())) {
+            this.parser.push(chunk)
+          }
+          else {
+            this.readable = false
+            break
+          }
+        }
+      }
+
+      return frame
+    }
+
+    FrameProducer.prototype.needFrame = function() {
+      this.needsReadable = true
+      this._maybeEmitReadable()
+    }
+
     FrameProducer.prototype._configChanged = function() {
       this.restart()
     }
@@ -302,23 +330,25 @@ module.exports = syrup.serial()
         .catch(forceEnd)
     }
 
-    FrameProducer.prototype._readBanner = function(out) {
+    FrameProducer.prototype._readBanner = function(socket) {
       log.info('Reading minicap banner')
-      return bannerutil.read(out).timeout(2000)
+      return bannerutil.read(socket).timeout(2000)
     }
 
-    FrameProducer.prototype._readFrames = function() {
-      var parser = this.socket.stream.pipe(new FrameParser())
-      var emit = this.emit.bind(this)
+    FrameProducer.prototype._readFrames = function(socket) {
+      this.needsReadable = true
 
-      function tryRead() {
-        for (var frame; (frame = parser.read());) {
-          emit('frame', frame)
-        }
+      socket.on('readable', function() {
+        this.readable = true
+        this._maybeEmitReadable()
+      }.bind(this))
+    }
+
+    FrameProducer.prototype._maybeEmitReadable = function() {
+      if (this.readable && this.needsReadable) {
+        this.needsReadable = false
+        this.emit('readable')
       }
-
-      tryRead()
-      parser.on('readable', tryRead)
     }
 
     function createServer() {
@@ -366,12 +396,21 @@ module.exports = syrup.serial()
           frameProducer.updateRotation(newRotation)
         })
 
-        frameProducer.on('frame', function(frame) {
-          broadcastSet.each(function(ws) {
-            ws.send(frame, {
-              binary: true
-            })
-          })
+        frameProducer.on('readable', function next() {
+          console.log('NEXT')
+          var frame
+          if ((frame = frameProducer.nextFrame())) {
+            Promise.settle([broadcastSet.values().map(function(ws) {
+              return new Promise(function(resolve/*, reject*/) {
+                ws.send(frame, {
+                  binary: true
+                }, resolve)
+              })
+            })]).then(next)
+          }
+          else {
+            frameProducer.needFrame()
+          }
         })
 
         frameProducer.on('error', function(err) {