#
# 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 cPickle
import gc
from tempfile import NamedTemporaryFile
__all__ = ['Broadcast']
# Holds broadcasted data received from Java, keyed by its id.
_broadcastRegistry = {}
def _from_id(bid):
from pyspark.broadcast import _broadcastRegistry
if bid not in _broadcastRegistry:
raise Exception("Broadcast variable '%s' not loaded!" % bid)
return _broadcastRegistry[bid]
class Broadcast(object):
"""
A broadcast variable created with L{SparkContext.broadcast()}.
Access its value through C{.value}.
Examples:
>>> from pyspark.context import SparkContext
>>> sc = SparkContext('local', 'test')
>>> b = sc.broadcast([1, 2, 3, 4, 5])
>>> b.value
[1, 2, 3, 4, 5]
>>> sc.parallelize([0, 0]).flatMap(lambda x: b.value).collect()
[1, 2, 3, 4, 5, 1, 2, 3, 4, 5]
>>> b.unpersist()
>>> large_broadcast = sc.broadcast(range(10000))
"""
def __init__(self, sc=None, value=None, pickle_registry=None, path=None):
"""
Should not be called directly by users -- use L{SparkContext.broadcast()}
instead.
"""
if sc is not None:
f = NamedTemporaryFile(delete=False, dir=sc._temp_dir)
self._path = self.dump(value, f)
self._jbroadcast = sc._jvm.PythonRDD.readBroadcastFromFile(sc._jsc, self._path)
self._pickle_registry = pickle_registry
else:
self._jbroadcast = None
self._path = path
def dump(self, value, f):
if isinstance(value, basestring):
if isinstance(value, unicode):
f.write('U')
value = value.encode('utf8')
else:
f.write('S')
f.write(value)
else:
f.write('P')
cPickle.dump(value, f, 2)
f.close()
return f.name
def load(self, path):
with open(path, 'rb', 1 << 20) as f:
flag = f.read(1)
data = f.read()
if flag == 'P':
# cPickle.loads() may create lots of objects, disable GC
# temporary for better performance
gc.disable()
try:
return cPickle.loads(data)
finally:
gc.enable()
else:
return data.decode('utf8') if flag == 'U' else data
@property
def value(self):
""" Return the broadcasted value
"""
if not hasattr(self, "_value") and self._path is not None:
self._value = self.load(self._path)
return self._value
def unpersist(self, blocking=False):
"""
Delete cached copies of this broadcast on the executors.
"""
if self._jbroadcast is None:
raise Exception("Broadcast can only be unpersisted in driver")
self._jbroadcast.unpersist(blocking)
os.unlink(self._path)
def __reduce__(self):
if self._jbroadcast is None:
raise Exception("Broadcast can only be serialized in driver")
self._pickle_registry.add(self)
return _from_id, (self._jbroadcast.id(),)
if __name__ == "__main__":
import doctest
doctest.testmod()
