Github user tdas commented on a diff in the pull request:
https://github.com/apache/spark/pull/2538#discussion_r18193898
--- Diff: python/pyspark/streaming/dstream.py ---
@@ -0,0 +1,633 @@
+#
+# 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 itertools import chain, ifilter, imap
+import operator
+import time
+from datetime import datetime
+
+from pyspark import RDD
+from pyspark.storagelevel import StorageLevel
+from pyspark.streaming.util import rddToFileName, RDDFunction
+from pyspark.rdd import portable_hash
+from pyspark.resultiterable import ResultIterable
+
+__all__ = ["DStream"]
+
+
+class DStream(object):
+ def __init__(self, jdstream, ssc, jrdd_deserializer):
+ self._jdstream = jdstream
+ self._ssc = ssc
+ self.ctx = ssc._sc
+ self._jrdd_deserializer = jrdd_deserializer
+ self.is_cached = False
+ self.is_checkpointed = False
+
+ def context(self):
+ """
+ Return the StreamingContext associated with this DStream
+ """
+ return self._ssc
+
+ def count(self):
+ """
+ Return a new DStream which contains the number of elements in this
DStream.
+ """
+ return self.mapPartitions(lambda i: [sum(1 for _ in i)]).sum()
+
+ def sum(self):
+ """
+ Add up the elements in this DStream.
+ """
+ return self.mapPartitions(lambda x: [sum(x)]).reduce(operator.add)
+
+ def filter(self, f):
+ """
+ Return a new DStream containing only the elements that satisfy
predicate.
+ """
+ def func(iterator):
+ return ifilter(f, iterator)
+ return self.mapPartitions(func, True)
+
+ def flatMap(self, f, preservesPartitioning=False):
+ """
+ Pass each value in the key-value pair DStream through flatMap
function
+ without changing the keys: this also retains the original RDD's
partition.
+ """
+ def func(s, iterator):
+ return chain.from_iterable(imap(f, iterator))
+ return self.mapPartitionsWithIndex(func, preservesPartitioning)
+
+ def map(self, f, preservesPartitioning=False):
+ """
+ Return a new DStream by applying a function to each element of
DStream.
+ """
+ def func(iterator):
+ return imap(f, iterator)
+ return self.mapPartitions(func, preservesPartitioning)
+
+ def mapPartitions(self, f, preservesPartitioning=False):
+ """
+ Return a new DStream by applying a function to each partition of
this DStream.
+ """
+ def func(s, iterator):
+ return f(iterator)
+ return self.mapPartitionsWithIndex(func, preservesPartitioning)
+
+ def mapPartitionsWithIndex(self, f, preservesPartitioning=False):
+ """
+ Return a new DStream by applying a function to each partition of
this DStream,
+ while tracking the index of the original partition.
+ """
+ return self.transform(lambda rdd: rdd.mapPartitionsWithIndex(f,
preservesPartitioning))
+
+ def reduce(self, func):
+ """
+ Return a new DStream by reduceing the elements of this RDD using
the specified
+ commutative and associative binary operator.
+ """
+ return self.map(lambda x: (None, x)).reduceByKey(func,
1).map(lambda x: x[1])
+
+ def reduceByKey(self, func, numPartitions=None):
+ """
+ Merge the value for each key using an associative reduce function.
+
+ This will also perform the merging locally on each mapper before
+ sending results to reducer, similarly to a "combiner" in MapReduce.
+
+ Output will be hash-partitioned with C{numPartitions} partitions,
or
+ the default parallelism level if C{numPartitions} is not specified.
+ """
+ return self.combineByKey(lambda x: x, func, func, numPartitions)
+
+ def combineByKey(self, createCombiner, mergeValue, mergeCombiners,
+ numPartitions=None):
+ """
+ Count the number of elements for each key, and return the result
to the
+ master as a dictionary
+ """
+ def func(rdd):
+ return rdd.combineByKey(createCombiner, mergeValue,
mergeCombiners, numPartitions)
+ return self.transform(func)
+
+ def partitionBy(self, numPartitions, partitionFunc=portable_hash):
+ """
+ Return a copy of the DStream partitioned using the specified
partitioner.
+ """
+ return self.transform(lambda rdd: rdd.partitionBy(numPartitions,
partitionFunc))
+
+ def foreach(self, func):
+ return self.foreachRDD(lambda _, rdd: rdd.foreach(func))
+
+ def foreachRDD(self, func):
+ """
+ Apply userdefined function to all RDD in a DStream.
+ This python implementation could be expensive because it uses
callback server
+ in order to apply function to RDD in DStream.
+ This is an output operator, so this DStream will be registered as
an output
+ stream and there materialized.
+ """
+ jfunc = RDDFunction(self.ctx, func, self._jrdd_deserializer)
+ api = self._ssc._jvm.PythonDStream
+ api.callForeachRDD(self._jdstream, jfunc)
+
+ def pprint(self):
+ """
+ Print the first ten elements of each RDD generated in this
DStream. This is an output
+ operator, so this DStream will be registered as an output stream
and there materialized.
+ """
+ def takeAndPrint(timestamp, rdd):
+ taken = rdd.take(11)
+ print "-------------------------------------------"
+ print "Time: %s" % datetime.fromtimestamp(timestamp / 1000.0)
+ print "-------------------------------------------"
+ for record in taken[:10]:
+ print record
+ if len(taken) > 10:
+ print "..."
+ print
+
+ self.foreachRDD(takeAndPrint)
+
+ def _first(self):
+ """
+ Return the first RDD in the stream.
+ """
+ return self._take(1)[0]
+
+ def _take(self, n):
+ """
+ Return the first `n` RDDs in the stream (will start and stop).
+ """
+ results = []
+
+ def take(_, rdd):
+ if rdd and len(results) < n:
+ results.extend(rdd.take(n - len(results)))
+
+ self.foreachRDD(take)
+
+ self._ssc.start()
+ while len(results) < n:
+ time.sleep(0.01)
+ self._ssc.stop(False, True)
+ return results
+
+ def _collect(self):
+ """
+ Collect each RDDs into the returned list.
+
+ :return: list, which will have the collected items.
+ """
+ result = []
+
+ def get_output(_, rdd):
+ r = rdd.collect()
+ result.append(r)
+ self.foreachRDD(get_output)
+ return result
+
+ def mapValues(self, f):
+ """
+ Pass each value in the key-value pair RDD through a map function
+ without changing the keys; this also retains the original RDD's
+ partitioning.
+ """
+ map_values_fn = lambda (k, v): (k, f(v))
+ return self.map(map_values_fn, preservesPartitioning=True)
+
+ def flatMapValues(self, f):
+ """
+ Pass each value in the key-value pair RDD through a flatMap
function
+ without changing the keys; this also retains the original RDD's
+ partitioning.
+ """
+ flat_map_fn = lambda (k, v): ((k, x) for x in f(v))
+ return self.flatMap(flat_map_fn, preservesPartitioning=True)
+
+ def glom(self):
+ """
+ Return a new DStream in which RDD is generated by applying glom()
+ to RDD of this DStream. Applying glom() to an RDD coalesces all
+ elements within each partition into an list.
+ """
+ def func(iterator):
+ yield list(iterator)
+ return self.mapPartitions(func)
+
+ def cache(self):
+ """
+ Persist this DStream with the default storage level
(C{MEMORY_ONLY_SER}).
+ """
+ self.is_cached = True
+ self.persist(StorageLevel.MEMORY_ONLY_SER)
+ return self
+
+ def persist(self, storageLevel):
+ """
+ Set this DStream's storage level to persist its values across
operations
+ after the first time it is computed. This can only be used to
assign
+ a new storage level if the DStream does not have a storage level
set yet.
+ """
+ self.is_cached = True
+ javaStorageLevel = self.ctx._getJavaStorageLevel(storageLevel)
+ self._jdstream.persist(javaStorageLevel)
+ return self
+
+ def checkpoint(self, interval):
+ """
+ Mark this DStream for checkpointing. It will be saved to a file
inside the
+ checkpoint directory set with L{SparkContext.setCheckpointDir()}
+
+ @param interval: time in seconds, after which generated RDD will
+ be checkpointed
+ """
+ self.is_checkpointed = True
+ self._jdstream.checkpoint(self._ssc._jduration(interval))
+ return self
+
+ def groupByKey(self, numPartitions=None):
+ """
+ Return a new DStream which contains group the values for each key
in the
+ DStream into a single sequence.
+ Hash-partitions the resulting RDD with into numPartitions
partitions in
+ the DStream.
+
+ Note: If you are grouping in order to perform an aggregation (such
as a
+ sum or average) over each key, using reduceByKey will provide much
+ better performance.
+ """
+ return self.transform(lambda rdd: rdd.groupByKey(numPartitions))
+
+ def countByValue(self):
+ """
+ Return new DStream which contains the count of each unique value
in this
+ DStreeam as a (value, count) pairs.
+ """
+ return self.map(lambda x: (x, None)).reduceByKey(lambda x, y:
None).count()
+
+ def saveAsTextFiles(self, prefix, suffix=None):
+ """
+ Save this DStream as a text file, using string representations of
elements.
+ """
+
+ def saveAsTextFile(time, rdd):
+ """
+ Closure to save element in RDD in DStream as Pickled data in
file.
+ This closure is called by py4j callback server.
+ """
+ path = rddToFileName(prefix, suffix, time)
+ rdd.saveAsTextFile(path)
+
+ return self.foreachRDD(saveAsTextFile)
+
+ def saveAsPickleFiles(self, prefix, suffix=None):
+ """
+ Save this DStream as a SequenceFile of serialized objects. The
serializer
+ used is L{pyspark.serializers.PickleSerializer}, default batch size
+ is 10.
+ """
+
+ def saveAsPickleFile(time, rdd):
+ """
+ Closure to save element in RDD in the DStream as Pickled data
in file.
+ This closure is called by py4j callback server.
+ """
+ path = rddToFileName(prefix, suffix, time)
+ rdd.saveAsPickleFile(path)
+
+ return self.foreachRDD(saveAsPickleFile)
+
+ def transform(self, func):
+ """
+ Return a new DStream in which each RDD is generated by applying a
function
+ on each RDD of 'this' DStream.
+ """
+ return TransformedDStream(self, lambda t, a: func(a), True)
+
+ def transformWithTime(self, func):
--- End diff --
This does not exist in Scala/Java API. Lets not add this.
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