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broadcast.py
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broadcast.py
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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 gc
import os
import socket
import sys
from tempfile import NamedTemporaryFile
import threading
from pyspark.cloudpickle import print_exec
from pyspark.java_gateway import local_connect_and_auth
from pyspark.serializers import ChunkedStream
from pyspark.util import _exception_message
if sys.version < '3':
import cPickle as pickle
else:
import pickle
unicode = str
__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,
sock_file=None):
"""
Should not be called directly by users -- use L{SparkContext.broadcast()}
instead.
"""
if sc is not None:
# we're on the driver. We want the pickled data to end up in a file (maybe encrypted)
f = NamedTemporaryFile(delete=False, dir=sc._temp_dir)
self._path = f.name
python_broadcast = sc._jvm.PythonRDD.setupBroadcast(self._path)
if sc._encryption_enabled:
# with encryption, we ask the jvm to do the encryption for us, we send it data
# over a socket
port, auth_secret = python_broadcast.setupEncryptionServer()
(encryption_sock_file, _) = local_connect_and_auth(port, auth_secret)
broadcast_out = ChunkedStream(encryption_sock_file, 8192)
else:
# no encryption, we can just write pickled data directly to the file from python
broadcast_out = f
self.dump(value, broadcast_out)
if sc._encryption_enabled:
python_broadcast.waitTillDataReceived()
self._jbroadcast = sc._jsc.broadcast(python_broadcast)
self._pickle_registry = pickle_registry
else:
# we're on an executor
self._jbroadcast = None
if sock_file is not None:
# the jvm is doing decryption for us. Read the value
# immediately from the sock_file
self._value = self.load(sock_file)
else:
# the jvm just dumps the pickled data in path -- we'll unpickle lazily when
# the value is requested
assert(path is not None)
self._path = path
def dump(self, value, f):
try:
pickle.dump(value, f, 2)
except pickle.PickleError:
raise
except Exception as e:
msg = "Could not serialize broadcast: %s: %s" \
% (e.__class__.__name__, _exception_message(e))
print_exec(sys.stderr)
raise pickle.PicklingError(msg)
f.close()
def load_from_path(self, path):
with open(path, 'rb', 1 << 20) as f:
return self.load(f)
def load(self, file):
# "file" could also be a socket
gc.disable()
try:
return pickle.load(file)
finally:
gc.enable()
@property
def value(self):
""" Return the broadcasted value
"""
if not hasattr(self, "_value") and self._path is not None:
self._value = self.load_from_path(self._path)
return self._value
def unpersist(self, blocking=False):
"""
Delete cached copies of this broadcast on the executors. If the
broadcast is used after this is called, it will need to be
re-sent to each executor.
:param blocking: Whether to block until unpersisting has completed
"""
if self._jbroadcast is None:
raise Exception("Broadcast can only be unpersisted in driver")
self._jbroadcast.unpersist(blocking)
def destroy(self):
"""
Destroy all data and metadata related to this broadcast variable.
Use this with caution; once a broadcast variable has been destroyed,
it cannot be used again. This method blocks until destroy has
completed.
"""
if self._jbroadcast is None:
raise Exception("Broadcast can only be destroyed in driver")
self._jbroadcast.destroy()
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(),)
class BroadcastPickleRegistry(threading.local):
""" Thread-local registry for broadcast variables that have been pickled
"""
def __init__(self):
self.__dict__.setdefault("_registry", set())
def __iter__(self):
for bcast in self._registry:
yield bcast
def add(self, bcast):
self._registry.add(bcast)
def clear(self):
self._registry.clear()
if __name__ == "__main__":
import doctest
(failure_count, test_count) = doctest.testmod()
if failure_count:
exit(-1)