Cannot connect to Python process in Spark Streaming

[canan chen]

I run pyspark streaming example queue_streaming.py. But run into the
following error, does anyone know what might be wrong ? Thanks

ERROR [2017-08-02 08:29:20,023] ({Stop-StreamingContext}
Logging.scala[logError]:91) - Cannot connect to Python process. It's
probably dead. Stopping StreamingContext.
py4j.Py4JException: Error while obtaining a new communication channel
    at py4j.CallbackClient.getConnectionLock(CallbackClient.java:218)
    at py4j.CallbackClient.sendCommand(CallbackClient.java:337)
    at py4j.CallbackClient.sendCommand(CallbackClient.java:316)
    at
py4j.reflection.PythonProxyHandler.invoke(PythonProxyHandler.java:103)
    at com.sun.proxy.$Proxy16.call(Unknown Source)
    at
org.apache.spark.streaming.api.python.TransformFunction.callPythonTransformFunction(PythonDStream.scala:92)
    at
org.apache.spark.streaming.api.python.TransformFunction.apply(PythonDStream.scala:78)
    at
org.apache.spark.streaming.api.python.PythonTransformedDStream.compute(PythonDStream.scala:246)
    at
org.apache.spark.streaming.dstream.DStream$$anonfun$getOrCompute$1$$anonfun$1$$anonfun$apply$7.apply(DStream.scala:341)
    at
org.apache.spark.streaming.dstream.DStream$$anonfun$getOrCompute$1$$anonfun$1$$anonfun$apply$7.apply(DStream.scala:341)
    at scala.util.DynamicVariable.withValue(DynamicVariable.scala:58)
    at
org.apache.spark.streaming.dstream.DStream$$anonfun$getOrCompute$1$$anonfun$1.apply(DStream.scala:340)
    at
org.apache.spark.streaming.dstream.DStream$$anonfun$getOrCompute$1$$anonfun$1.apply(DStream.scala:340)
    at
org.apache.spark.streaming.dstream.DStream.createRDDWithLocalProperties(DStream.scala:415)
    at
org.apache.spark.streaming.dstream.DStream$$anonfun$getOrCompute$1.apply(DStream.scala:335)
    at
org.apache.spark.streaming.dstream.DStream$$anonfun$getOrCompute$1.apply(DStream.scala:333)
    at scala.Option.orElse(Option.scala:289)
    at
org.apache.spark.streaming.dstream.DStream.getOrCompute(DStream.scala:330)
    at
org.apache.spark.streaming.dstream.ForEachDStream.generateJob(ForEachDStream.scala:48)
    at
org.apache.spark.streaming.DStreamGraph$$anonfun$1.apply(DStreamGraph.scala:117)
    at
org.apache.spark.streaming.DStreamGraph$$anonfun$1.apply(DStreamGraph.scala:116)
    at
scala.collection.TraversableLike$$anonfun$flatMap$1.apply(TraversableLike.scala:241)
    at
scala.collection.TraversableLike$$anonfun$flatMap$1.apply(TraversableLike.scala:241)
    at
scala.collection.mutable.ResizableArray$class.foreach(ResizableArray.scala:59)
    at scala.collection.mutable.ArrayBuffer.foreach(ArrayBuffer.scala:48)
    at
scala.collection.TraversableLike$class.flatMap(TraversableLike.scala:241)
    at scala.collection.AbstractTraversable.flatMap(Traversable.scala:104)
    at
org.apache.spark.streaming.DStreamGraph.generateJobs(DStreamGraph.scala:116)
    at
org.apache.spark.streaming.scheduler.JobGenerator$$anonfun$3.apply(JobGenerator.scala:249)
    at
org.apache.spark.streaming.scheduler.JobGenerator$$anonfun$3.apply(JobGenerator.scala:247)
    at scala.util.Try$.apply(Try.scala:192)