[SPARK-5155] [PYSPARK] [STREAMING] Mqtt streaming support in Python

This PR is based on #4229, thanks prabeesh.

Closes #4229

Author: Prabeesh K <prabsmails@gmail.com>
Author: zsxwing <zsxwing@gmail.com>
Author: prabs <prabsmails@gmail.com>
Author: Prabeesh K <prabeesh.k@namshi.com>

Closes #7833 from zsxwing/pr4229 and squashes the following commits:

9570bec [zsxwing] Fix the variable name and check null in finally
4a9c79e [zsxwing] Fix pom.xml indentation
abf5f18 [zsxwing] Merge branch 'master' into pr4229
935615c [zsxwing] Fix the flaky MQTT tests
47278c5 [zsxwing] Include the project class files
478f844 [zsxwing] Add unpack
5f8a1d4 [zsxwing] Make the maven build generate the test jar for Python MQTT tests
734db99 [zsxwing] Merge branch 'master' into pr4229
126608a [Prabeesh K] address the comments
b90b709 [Prabeesh K] Merge pull request #1 from zsxwing/pr4229
d07f454 [zsxwing] Register StreamingListerner before starting StreamingContext; Revert unncessary changes; fix the python unit test
a6747cb [Prabeesh K] wait for starting the receiver before publishing data
87fc677 [Prabeesh K] address the comments:
97244ec [zsxwing] Make sbt build the assembly test jar for streaming mqtt
80474d1 [Prabeesh K] fix
1f0cfe9 [Prabeesh K] python style fix
e1ee016 [Prabeesh K] scala style fix
a5a8f9f [Prabeesh K] added Python test
9767d82 [Prabeesh K] implemented Python-friendly class
a11968b [Prabeesh K] fixed python style
795ec27 [Prabeesh K] address comments
ee387ae [Prabeesh K] Fix assembly jar location of mqtt-assembly
3f4df12 [Prabeesh K] updated version
b34c3c1 [prabs] adress comments
3aa7fff [prabs] Added Python streaming mqtt word count example
b7d42ff [prabs] Mqtt streaming support in Python

1 files changed, 72 insertions, 0 deletions

diff --git a/python/pyspark/streaming/mqtt.py b/python/pyspark/streaming/mqtt.py
new file mode 100644
index 0000000000..f06598971c
--- /dev/null
+++ b/python/pyspark/streaming/mqtt.py
@@ -0,0 +1,72 @@
+#
+# 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.java_gateway 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))