python/pyspark/streaming/mqtt.py

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from py4j.protocol import Py4JJavaError

from pyspark.storagelevel import StorageLevel
from pyspark.serializers import UTF8Deserializer
from pyspark.streaming import DStream

__all__ = ['MQTTUtils']


class MQTTUtils(object):

    @staticmethod
    def createStream(ssc, brokerUrl, topic,
                     storageLevel=StorageLevel.MEMORY_AND_DISK_SER_2):
        """
        Create an input stream that pulls messages from a Mqtt Broker.

        :param ssc:  StreamingContext object
        :param brokerUrl:  Url of remote mqtt publisher
        :param topic:  topic name to subscribe to
        :param storageLevel:  RDD storage level.
        :return: A DStream object
        """
        jlevel = ssc._sc._getJavaStorageLevel(storageLevel)

        try:
            helperClass = ssc._jvm.java.lang.Thread.currentThread().getContextClassLoader() \
                .loadClass("org.apache.spark.streaming.mqtt.MQTTUtilsPythonHelper")
            helper = helperClass.newInstance()
            jstream = helper.createStream(ssc._jssc, brokerUrl, topic, jlevel)
        except Py4JJavaError as e:
            if 'ClassNotFoundException' in str(e.java_exception):
                MQTTUtils._printErrorMsg(ssc.sparkContext)
            raise e

        return DStream(jstream, ssc, UTF8Deserializer())

    @staticmethod
    def _printErrorMsg(sc):
        print("""
________________________________________________________________________________________________

  Spark Streaming's MQTT libraries not found in class path. Try one of the following.

  1. Include the MQTT library and its dependencies with in the
     spark-submit command as

     $ bin/spark-submit --packages org.apache.spark:spark-streaming-mqtt:%s ...

  2. Download the JAR of the artifact from Maven Central http://search.maven.org/,
     Group Id = org.apache.spark, Artifact Id = spark-streaming-mqtt-assembly, Version = %s.
     Then, include the jar in the spark-submit command as

     $ bin/spark-submit --jars <spark-streaming-mqtt-assembly.jar> ...
________________________________________________________________________________________________
""" % (sc.version, sc.version))