Improved documentation for spark custom receiver

docs/streaming-custom-receivers.md

@@ -7,10 +7,45 @@ A "Spark Streaming" receiver can be a simple network stream, streams of messages
 
 This guide shows the programming model and features by walking through a simple sample receiver and corresponding Spark Streaming application.
 
+### Write a simple receiver
 
-## A quick and naive walk-through
+This starts with implementing [NetworkReceiver](#References)
 
-### Write a simple receiver
+Following is a simple socket text-stream receiver.
+
+{% highlight scala %}
+
+       class SocketTextStreamReceiver(host: String,
+                                      port: Int
+                                       ) extends NetworkReceiver[String] {
+
+         protected lazy val blocksGenerator: BlockGenerator =
+           new BlockGenerator(StorageLevel.MEMORY_ONLY_SER_2)
+
+         protected def onStart() = {
+           blocksGenerator.start()
+           val socket = new Socket(host, port)
+           val dataInputStream = new BufferedReader(new InputStreamReader(socket.getInputStream(), "UTF-8"))
+           var data: String = dataInputStream.readLine()
+           while (data != null) {
+             blocksGenerator += data
+             data = dataInputStream.readLine()
+           }
+         }
+
+         protected def onStop() {
+           blocksGenerator.stop()
+         }
+
+       }
+
+{% endhighlight %}
+
+
+All we did here is extended NetworkReceiver and called blockGenerator's API method (i.e. +=) to push our blocks of data. Please refer to scala-docs of NetworkReceiver for more details.
+
+
+### An Actor as Receiver.
 
 This starts with implementing [Actor](#References)
 
@@ -46,7 +81,16 @@ All we did here is mixed in trait Receiver and called pushBlock api method to pu
 
 {% endhighlight %}
 
-* Plug-in the actor configuration into the spark streaming context and create a DStream.
+* Plug-in the custom receiver into the spark streaming context and create a DStream.
+
+{% highlight scala %}
+
+    val lines = ssc.networkStream[String](new SocketTextStreamReceiver(
+      "localhost", 8445))
+
+{% endhighlight %}
+
+* OR Plug-in the actor as receiver into the spark streaming context and create a DStream.
 
 {% highlight scala %}
 
@@ -99,3 +143,4 @@ _A more comprehensive example is provided in the spark streaming examples_
 ## References
 
 1.[Akka Actor documentation](http://doc.akka.io/docs/akka/2.0.5/scala/actors.html)
+2.[NetworkReceiver](http://spark-project.org/docs/latest/api/streaming/index.html#spark.streaming.dstream.NetworkReceiver)