Passing hostname to netty - networking

Question

Background: I've got two machines with identical hostnames, I need to set up a local spark cluster for testing, setting up a master and a worker works fine, but trying to run an application with the driver causes problems, netty doesn't seem to be picking the correct host (regardless of what I put in there, it just picks the first host).
Identical hostname:
$ dig +short corehost
192.168.0.100
192.168.0.101
Spark config (used by master and the local worker):
export SPARK_LOCAL_DIRS=/some/dir
export SPARK_LOCAL_IP=corehost // i tried various like 192.168.0.x for
export SPARK_MASTER_IP=corehost // local, master and the driver
export SPARK_MASTER_PORT=7077
export SPARK_WORKER_CORES=2
export SPARK_WORKER_MEMORY=2g
export SPARK_WORKER_INSTANCES=2
export SPARK_WORKER_DIR=/some/dir
Spark starts up and I can see the worker in the web-ui.
When I run the spark "job" below:
val conf = new SparkConf().setAppName("AaA")
// tried 192.168.0.x and localhost
.setMaster("spark://corehost:7077")
val sc = new SparkContext(conf)
I get this exception:
15/04/02 12:34:04 INFO SparkContext: Running Spark version 1.3.0
15/04/02 12:34:04 WARN Utils: Your hostname, corehost resolves to a loopback address: 127.0.0.1; using 192.168.0.100 instead (on interface en1)
15/04/02 12:34:04 WARN Utils: Set SPARK_LOCAL_IP if you need to bind to another address
15/04/02 12:34:05 ERROR NettyTransport: failed to bind to corehost.home/192.168.0.101:0, shutting down Netty transport
...
Exception in thread "main" java.net.BindException: Failed to bind to: corehost.home/192.168.0.101:0: Service 'sparkDriver' failed after 16 retries!
at org.jboss.netty.bootstrap.ServerBootstrap.bind(ServerBootstrap.java:272)
at akka.remote.transport.netty.NettyTransport$$anonfun$listen$1.apply(NettyTransport.scala:393)
at akka.remote.transport.netty.NettyTransport$$anonfun$listen$1.apply(NettyTransport.scala:389)
at scala.util.Success$$anonfun$map$1.apply(Try.scala:206)
at scala.util.Try$.apply(Try.scala:161)
at scala.util.Success.map(Try.scala:206)
at scala.concurrent.Future$$anonfun$map$1.apply(Future.scala:235)
at scala.concurrent.Future$$anonfun$map$1.apply(Future.scala:235)
at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:32)
at akka.dispatch.BatchingExecutor$Batch$$anonfun$run$1.processBatch$1(BatchingExecutor.scala:67)
at akka.dispatch.BatchingExecutor$Batch$$anonfun$run$1.apply$mcV$sp(BatchingExecutor.scala:82)
at akka.dispatch.BatchingExecutor$Batch$$anonfun$run$1.apply(BatchingExecutor.scala:59)
at akka.dispatch.BatchingExecutor$Batch$$anonfun$run$1.apply(BatchingExecutor.scala:59)
at scala.concurrent.BlockContext$.withBlockContext(BlockContext.scala:72)
at akka.dispatch.BatchingExecutor$Batch.run(BatchingExecutor.scala:58)
at akka.dispatch.TaskInvocation.run(AbstractDispatcher.scala:41)
at akka.dispatch.ForkJoinExecutorConfigurator$AkkaForkJoinTask.exec(AbstractDispatcher.scala:393)
at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)
15/04/02 12:34:05 INFO RemoteActorRefProvider$RemotingTerminator: Shutting down remote daemon.
15/04/02 12:34:05 INFO RemoteActorRefProvider$RemotingTerminator: Remote daemon shut down; proceeding with flushing remote transports.
15/04/02 12:34:05 INFO RemoteActorRefProvider$RemotingTerminator: Remoting shut down.
Process finished with exit code 1
Not sure how to proceed... its a whole jungle of ip addresses.
Not sure if this is a netty issue either.

Answer 1

My experience with the identical problem is that it revolves around setting things up locally. Try being more verbose in your spark driver code, add the SPARK_LOCAL_IP and driver host ip to the config:
val conf = new SparkConf().setAppName("AaA")
.setMaster("spark://localhost:7077")
.set("spark.local.ip","192.168.1.100")
.set("spark.driver.host","192.168.1.100")
This should tell netty which of the two identical hosts to use.