When submitting a spark streaming recevier, how to specify host without "failing through"? - scala

Question

I want to create a server socket to listen on, on a host that I know the ip and hostname ahead of time (and it shows up with that hostname in the yarn node list) . But I can't seem to get it to listen on that host without letting it fail an arbitrary number of times before hand.
There's a Flume receiver that has the sort of host-specific functionality I'm looking for.
FlumeUtils.createStream(streamingContext, [chosen machine's hostname], [chosen port])
My receiver code:
class TCPServerReceiver(hostname: String, port: Int)
extends Receiver[String](StorageLevel.MEMORY_AND_DISK_2) with Logging {
def onStart() {
// Start the thread that receives data over a connection
new Thread("Socket Receiver") {
override def run() { receive() }
}.start()
}
def onStop() {
}
private def receive() {
/* This is where the job fails until it happens to start on the correct host */
val server = new ServerSocket(port, 50, InetAddress.getByName(hostname))
var userInput: String = null
while (true) {
try {
val s = server.accept()
val in = new BufferedReader(new InputStreamReader(s.getInputStream()))
userInput = in.readLine()
while (!isStopped && userInput != null) {
store(userInput)
userInput = in.readLine()
}
} catch {
case e: java.net.ConnectException =>
restart("Error connecting to " + port, e)
case t: Throwable =>
restart("Error receiving data", t)
}
}
}
}
And then to test it while it's running:
echo 'this is a test' | nc <hostname> <port>
This all works when I run as a local client, but when it's submitted to a yarn cluster, the logs show it trying to run in other containers on different hosts and all of them fail because the hostname doesn't match that of the container:
java.net.BindException: Cannot assign requested address
Eventually (after several minutes), it does create the socket once the receiver tries to start on the correct host, so the above code does work, but it takes a substantial amount of "boot time" and I'm worried that adding more nodes will cause it to take even longer!
Is there a way of ensuring that this receiver starts on the correct host on the first try?

Answer 1

The custom TCPServerReceiver implementation should also implement:
def preferredLocation: Option[String]
Override this to specify a preferred location (hostname).
In this case, something like:
def preferredLocation = Some(hostname)