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#
# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements. See the NOTICE file distributed with
# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
# the License. You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
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_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))
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