support kafka in Python

Author: Davies Liu

python/pyspark/streaming/kafka.py

@@ -0,0 +1,71 @@
+#
+# 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_collections import MapConverter
+from py4j.java_gateway import java_import, Py4JError
+
+from pyspark.storagelevel import StorageLevel
+from pyspark.serializers import PairDeserializer, UTF8Deserializer
+from pyspark.streaming import DStream
+
+__all__ = ['KafkaUtils']
+
+
+class KafkaUtils(object):
+
+    @staticmethod
+    def createStream(ssc, zkQuorum, groupId, topics,
+                     storageLevel=StorageLevel.MEMORY_AND_DISK_SER_2,
+                     keyDecoder=None, valueDecoder=None):
+        """
+        Create an input stream that pulls messages from a Kafka Broker.
+
+        :param ssc:  StreamingContext object
+        :param zkQuorum:  Zookeeper quorum (hostname:port,hostname:port,..).
+        :param groupId:  The group id for this consumer.
+        :param topics:  Dict of (topic_name -> numPartitions) to consume.
+                        Each partition is consumed in its own thread.
+        :param storageLevel:  RDD storage level.
+        :param keyDecoder:  A function used to decode key
+        :param valueDecoder:  A function used to decode value
+        :return: A DStream object
+        """
+        java_import(ssc._jvm, "org.apache.spark.streaming.kafka.KafkaUtils")
+
+        if not isinstance(topics, dict):
+            raise TypeError("topics should be dict")
+        jtopics = MapConverter().convert(topics, ssc.sparkContext._gateway._gateway_client)
+        jlevel = ssc._sc._getJavaStorageLevel(storageLevel)
+        try:
+            jstream = ssc._jvm.KafkaUtils.createStream(ssc._jssc, zkQuorum, groupId, jtopics, jlevel)
+        except Py4JError, e:
+            if 'call a package' in e.message:
+                print "No kafka package, please build it and add it into classpath:"
+                print " $ sbt/sbt streaming-kafka/package"
+                print " $ bin/submit --driver-class-path external/kafka/target/scala-2.10/" \
+                      "spark-streaming-kafka_2.10-1.3.0-SNAPSHOT.jar"
+                raise Exception("No kafka package")
+            raise e
+        ser = PairDeserializer(UTF8Deserializer(), UTF8Deserializer())
+        stream = DStream(jstream, ssc, ser)
+
+        if keyDecoder is not None:
+            stream = stream.map(lambda (k, v): (keyDecoder(k), v))
+        if valueDecoder is not None:
+            stream = stream.mapValues(valueDecoder)
+        return stream