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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.
#
import os
import shutil
import sys
from threading import Lock
from tempfile import NamedTemporaryFile
from collections import namedtuple
from pyspark import accumulators
from pyspark.accumulators import Accumulator
from pyspark.broadcast import Broadcast
from pyspark.conf import SparkConf
from pyspark.files import SparkFiles
from pyspark.java_gateway import launch_gateway
from pyspark.serializers import PickleSerializer, BatchedSerializer, UTF8Deserializer
from pyspark.storagelevel import StorageLevel
from pyspark import rdd
from pyspark.rdd import RDD
from py4j.java_collections import ListConverter
class SparkContext(object):
"""
Main entry point for Spark functionality. A SparkContext represents the
connection to a Spark cluster, and can be used to create L{RDD}s and
broadcast variables on that cluster.
"""
_gateway = None
_jvm = None
_writeToFile = None
_next_accum_id = 0
_active_spark_context = None
_lock = Lock()
_python_includes = None # zip and egg files that need to be added to PYTHONPATH
def __init__(self, master=None, appName=None, sparkHome=None, pyFiles=None,
environment=None, batchSize=1024, serializer=PickleSerializer(), conf=None,
gateway=None):
"""
Create a new SparkContext. At least the master and app name should be set,
either through the named parameters here or through C{conf}.
@param master: Cluster URL to connect to
(e.g. mesos://host:port, spark://host:port, local[4]).
@param appName: A name for your job, to display on the cluster web UI.
@param sparkHome: Location where Spark is installed on cluster nodes.
@param pyFiles: Collection of .zip or .py files to send to the cluster
and add to PYTHONPATH. These can be paths on the local file
system or HDFS, HTTP, HTTPS, or FTP URLs.
@param environment: A dictionary of environment variables to set on
worker nodes.
@param batchSize: The number of Python objects represented as a single
Java object. Set 1 to disable batching or -1 to use an
unlimited batch size.
@param serializer: The serializer for RDDs.
@param conf: A L{SparkConf} object setting Spark properties.
@param gateway: Use an existing gateway and JVM, otherwise a new JVM
will be instatiated.
>>> from pyspark.context import SparkContext
>>> sc = SparkContext('local', 'test')
>>> sc2 = SparkContext('local', 'test2') # doctest: +IGNORE_EXCEPTION_DETAIL
Traceback (most recent call last):
...
ValueError:...
"""
if rdd._extract_concise_traceback() is not None:
self._callsite = rdd._extract_concise_traceback()
else:
tempNamedTuple = namedtuple("Callsite", "function file linenum")
self._callsite = tempNamedTuple(function=None, file=None, linenum=None)
SparkContext._ensure_initialized(self, gateway=gateway)
self.environment = environment or {}
self._conf = conf or SparkConf(_jvm=self._jvm)
self._batchSize = batchSize # -1 represents an unlimited batch size
self._unbatched_serializer = serializer
if batchSize == 1:
self.serializer = self._unbatched_serializer
else:
self.serializer = BatchedSerializer(self._unbatched_serializer,
batchSize)
# Set any parameters passed directly to us on the conf
if master:
self._conf.setMaster(master)
if appName:
self._conf.setAppName(appName)
if sparkHome:
self._conf.setSparkHome(sparkHome)
if environment:
for key, value in environment.iteritems():
self._conf.setExecutorEnv(key, value)
# Check that we have at least the required parameters
if not self._conf.contains("spark.master"):
raise Exception("A master URL must be set in your configuration")
if not self._conf.contains("spark.app.name"):
raise Exception("An application name must be set in your configuration")
# Read back our properties from the conf in case we loaded some of them from
# the classpath or an external config file
self.master = self._conf.get("spark.master")
self.appName = self._conf.get("spark.app.name")
self.sparkHome = self._conf.get("spark.home", None)
for (k, v) in self._conf.getAll():
if k.startswith("spark.executorEnv."):
varName = k[len("spark.executorEnv."):]
self.environment[varName] = v
# Create the Java SparkContext through Py4J
self._jsc = self._initialize_context(self._conf._jconf)
# Create a single Accumulator in Java that we'll send all our updates through;
# they will be passed back to us through a TCP server
self._accumulatorServer = accumulators._start_update_server()
(host, port) = self._accumulatorServer.server_address
self._javaAccumulator = self._jsc.accumulator(
self._jvm.java.util.ArrayList(),
self._jvm.PythonAccumulatorParam(host, port))
self.pythonExec = os.environ.get("PYSPARK_PYTHON", 'python')
# Broadcast's __reduce__ method stores Broadcast instances here.
# This allows other code to determine which Broadcast instances have
# been pickled, so it can determine which Java broadcast objects to
# send.
self._pickled_broadcast_vars = set()
SparkFiles._sc = self
root_dir = SparkFiles.getRootDirectory()
sys.path.append(root_dir)
# Deploy any code dependencies specified in the constructor
self._python_includes = list()
for path in (pyFiles or []):
self.addPyFile(path)
# Create a temporary directory inside spark.local.dir:
local_dir = self._jvm.org.apache.spark.util.Utils.getLocalDir(self._jsc.sc().conf())
self._temp_dir = \
self._jvm.org.apache.spark.util.Utils.createTempDir(local_dir).getAbsolutePath()
# Initialize SparkContext in function to allow subclass specific initialization
def _initialize_context(self, jconf):
return self._jvm.JavaSparkContext(jconf)
@classmethod
def _ensure_initialized(cls, instance=None, gateway=None):
with SparkContext._lock:
if not SparkContext._gateway:
SparkContext._gateway = gateway or launch_gateway()
SparkContext._jvm = SparkContext._gateway.jvm
SparkContext._writeToFile = SparkContext._jvm.PythonRDD.writeToFile
if instance:
if SparkContext._active_spark_context and SparkContext._active_spark_context != instance:
currentMaster = SparkContext._active_spark_context.master
currentAppName = SparkContext._active_spark_context.appName
callsite = SparkContext._active_spark_context._callsite
# Raise error if there is already a running Spark context
raise ValueError("Cannot run multiple SparkContexts at once; existing SparkContext(app=%s, master=%s)" \
" created by %s at %s:%s " \
% (currentAppName, currentMaster, callsite.function, callsite.file, callsite.linenum))
else:
SparkContext._active_spark_context = instance
@classmethod
def setSystemProperty(cls, key, value):
"""
Set a Java system property, such as spark.executor.memory. This must
must be invoked before instantiating SparkContext.
"""
SparkContext._ensure_initialized()
SparkContext._jvm.java.lang.System.setProperty(key, value)
@property
def defaultParallelism(self):
"""
Default level of parallelism to use when not given by user (e.g. for
reduce tasks)
"""
return self._jsc.sc().defaultParallelism()
def __del__(self):
self.stop()
def stop(self):
"""
Shut down the SparkContext.
"""
if self._jsc:
self._jsc.stop()
self._jsc = None
if self._accumulatorServer:
self._accumulatorServer.shutdown()
self._accumulatorServer = None
with SparkContext._lock:
SparkContext._active_spark_context = None
def parallelize(self, c, numSlices=None):
"""
Distribute a local Python collection to form an RDD.
>>> sc.parallelize(range(5), 5).glom().collect()
[[0], [1], [2], [3], [4]]
"""
numSlices = numSlices or self.defaultParallelism
# Calling the Java parallelize() method with an ArrayList is too slow,
# because it sends O(n) Py4J commands. As an alternative, serialized
# objects are written to a file and loaded through textFile().
tempFile = NamedTemporaryFile(delete=False, dir=self._temp_dir)
# Make sure we distribute data evenly if it's smaller than self.batchSize
if "__len__" not in dir(c):
c = list(c) # Make it a list so we can compute its length
batchSize = min(len(c) // numSlices, self._batchSize)
if batchSize > 1:
serializer = BatchedSerializer(self._unbatched_serializer,
batchSize)
else:
serializer = self._unbatched_serializer
serializer.dump_stream(c, tempFile)
tempFile.close()
readRDDFromFile = self._jvm.PythonRDD.readRDDFromFile
jrdd = readRDDFromFile(self._jsc, tempFile.name, numSlices)
return RDD(jrdd, self, serializer)
def textFile(self, name, minSplits=None):
"""
Read a text file from HDFS, a local file system (available on all
nodes), or any Hadoop-supported file system URI, and return it as an
RDD of Strings.
"""
minSplits = minSplits or min(self.defaultParallelism, 2)
return RDD(self._jsc.textFile(name, minSplits), self,
UTF8Deserializer())
def _checkpointFile(self, name, input_deserializer):
jrdd = self._jsc.checkpointFile(name)
return RDD(jrdd, self, input_deserializer)
def union(self, rdds):
"""
Build the union of a list of RDDs.
This supports unions() of RDDs with different serialized formats,
although this forces them to be reserialized using the default
serializer:
>>> path = os.path.join(tempdir, "union-text.txt")
>>> with open(path, "w") as testFile:
... testFile.write("Hello")
>>> textFile = sc.textFile(path)
>>> textFile.collect()
[u'Hello']
>>> parallelized = sc.parallelize(["World!"])
>>> sorted(sc.union([textFile, parallelized]).collect())
[u'Hello', 'World!']
"""
first_jrdd_deserializer = rdds[0]._jrdd_deserializer
if any(x._jrdd_deserializer != first_jrdd_deserializer for x in rdds):
rdds = [x._reserialize() for x in rdds]
first = rdds[0]._jrdd
rest = [x._jrdd for x in rdds[1:]]
rest = ListConverter().convert(rest, self._gateway._gateway_client)
return RDD(self._jsc.union(first, rest), self,
rdds[0]._jrdd_deserializer)
def broadcast(self, value):
"""
Broadcast a read-only variable to the cluster, returning a
L{Broadcast<pyspark.broadcast.Broadcast>}
object for reading it in distributed functions. The variable will be
sent to each cluster only once.
"""
pickleSer = PickleSerializer()
pickled = pickleSer.dumps(value)
jbroadcast = self._jsc.broadcast(bytearray(pickled))
return Broadcast(jbroadcast.id(), value, jbroadcast,
self._pickled_broadcast_vars)
def accumulator(self, value, accum_param=None):
"""
Create an L{Accumulator} with the given initial value, using a given
L{AccumulatorParam} helper object to define how to add values of the
data type if provided. Default AccumulatorParams are used for integers
and floating-point numbers if you do not provide one. For other types,
a custom AccumulatorParam can be used.
"""
if accum_param is None:
if isinstance(value, int):
accum_param = accumulators.INT_ACCUMULATOR_PARAM
elif isinstance(value, float):
accum_param = accumulators.FLOAT_ACCUMULATOR_PARAM
elif isinstance(value, complex):
accum_param = accumulators.COMPLEX_ACCUMULATOR_PARAM
else:
raise Exception("No default accumulator param for type %s" % type(value))
SparkContext._next_accum_id += 1
return Accumulator(SparkContext._next_accum_id - 1, value, accum_param)
def addFile(self, path):
"""
Add a file to be downloaded with this Spark job on every node.
The C{path} passed can be either a local file, a file in HDFS
(or other Hadoop-supported filesystems), or an HTTP, HTTPS or
FTP URI.
To access the file in Spark jobs, use
L{SparkFiles.get(path)<pyspark.files.SparkFiles.get>} to find its
download location.
>>> from pyspark import SparkFiles
>>> path = os.path.join(tempdir, "test.txt")
>>> with open(path, "w") as testFile:
... testFile.write("100")
>>> sc.addFile(path)
>>> def func(iterator):
... with open(SparkFiles.get("test.txt")) as testFile:
... fileVal = int(testFile.readline())
... return [x * 100 for x in iterator]
>>> sc.parallelize([1, 2, 3, 4]).mapPartitions(func).collect()
[100, 200, 300, 400]
"""
self._jsc.sc().addFile(path)
def clearFiles(self):
"""
Clear the job's list of files added by L{addFile} or L{addPyFile} so
that they do not get downloaded to any new nodes.
"""
# TODO: remove added .py or .zip files from the PYTHONPATH?
self._jsc.sc().clearFiles()
def addPyFile(self, path):
"""
Add a .py or .zip dependency for all tasks to be executed on this
SparkContext in the future. The C{path} passed can be either a local
file, a file in HDFS (or other Hadoop-supported filesystems), or an
HTTP, HTTPS or FTP URI.
"""
self.addFile(path)
(dirname, filename) = os.path.split(path) # dirname may be directory or HDFS/S3 prefix
if filename.endswith('.zip') or filename.endswith('.ZIP') or filename.endswith('.egg'):
self._python_includes.append(filename)
sys.path.append(os.path.join(SparkFiles.getRootDirectory(), filename)) # for tests in local mode
def setCheckpointDir(self, dirName):
"""
Set the directory under which RDDs are going to be checkpointed. The
directory must be a HDFS path if running on a cluster.
"""
self._jsc.sc().setCheckpointDir(dirName)
def _getJavaStorageLevel(self, storageLevel):
"""
Returns a Java StorageLevel based on a pyspark.StorageLevel.
"""
if not isinstance(storageLevel, StorageLevel):
raise Exception("storageLevel must be of type pyspark.StorageLevel")
newStorageLevel = self._jvm.org.apache.spark.storage.StorageLevel
return newStorageLevel(storageLevel.useDisk, storageLevel.useMemory,
storageLevel.deserialized, storageLevel.replication)
def setJobGroup(self, groupId, description):
"""
Assigns a group ID to all the jobs started by this thread until the group ID is set to a
different value or cleared.
Often, a unit of execution in an application consists of multiple Spark actions or jobs.
Application programmers can use this method to group all those jobs together and give a
group description. Once set, the Spark web UI will associate such jobs with this group.
"""
self._jsc.setJobGroup(groupId, description)
def setLocalProperty(self, key, value):
"""
Set a local property that affects jobs submitted from this thread, such as the
Spark fair scheduler pool.
"""
self._jsc.setLocalProperty(key, value)
def getLocalProperty(self, key):
"""
Get a local property set in this thread, or null if it is missing. See
L{setLocalProperty}
"""
return self._jsc.getLocalProperty(key)
def sparkUser(self):
"""
Get SPARK_USER for user who is running SparkContext.
"""
return self._jsc.sc().sparkUser()
def _test():
import atexit
import doctest
import tempfile
globs = globals().copy()
globs['sc'] = SparkContext('local[4]', 'PythonTest', batchSize=2)
globs['tempdir'] = tempfile.mkdtemp()
atexit.register(lambda: shutil.rmtree(globs['tempdir']))
(failure_count, test_count) = doctest.testmod(globs=globs)
globs['sc'].stop()
if failure_count:
exit(-1)
if __name__ == "__main__":
_test()
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