Github user mateiz commented on a diff in the pull request:
https://github.com/apache/spark/pull/1460#discussion_r15264650
--- Diff: python/pyspark/shuffle.py ---
@@ -0,0 +1,378 @@
+#
+# 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 sys
+import platform
+import shutil
+import warnings
+
+from pyspark.serializers import BatchedSerializer, PickleSerializer
+
+try:
+ import psutil
+
+ def get_used_memory():
+ self = psutil.Process(os.getpid())
+ return self.memory_info().rss >> 20
+
+except ImportError:
+
+ def get_used_memory():
+ if platform.system() == 'Linux':
+ for line in open('/proc/self/status'):
+ if line.startswith('VmRSS:'):
+ return int(line.split()[1]) >> 10
+ else:
+ warnings.warn("please install psutil to get accurate memory
usage")
+ if platform.system() == "Darwin":
+ import resource
+ return resource.getrusage(resource.RUSAGE_SELF).ru_maxrss
>> 20
+ # TODO: support windows
+ return 0
+
+
+class Aggregator(object):
+
+ def __init__(self, creator, combiner, mergeCombiner=None):
+ self.creator = creator
+ self.combiner = combiner
+ self.mergeCombiner = mergeCombiner or combiner
+
+
+class Merger(object):
+
+ """
+ merge shuffled data together by aggregator
+ """
+
+ def __init__(self, aggregator):
+ self.agg = aggregator
+
+ def combine(self, iterator):
+ """ combine the items by creator and combiner """
+ raise NotImplementedError
+
+ def merge(self, iterator):
+ """ merge the combined items by mergeCombiner """
+ raise NotImplementedError
+
+ def iteritems(self):
+ """ return the merged items ad iterator """
+ raise NotImplementedError
+
+
+class InMemoryMerger(Merger):
+
+ """
+ In memory merger based on in-memory dict.
+ """
+
+ def __init__(self, aggregator):
+ Merger.__init__(self, aggregator)
+ self.data = {}
+
+ def combine(self, iterator):
+ """ combine the items by creator and combiner """
+ # speed up attributes lookup
+ d, creator, comb = self.data, self.agg.creator, self.agg.combiner
+ for k, v in iterator:
+ d[k] = comb(d[k], v) if k in d else creator(v)
+
+ def merge(self, iterator):
+ """ merge the combined items by mergeCombiner """
+ # speed up attributes lookup
+ d, comb = self.data, self.agg.mergeCombiner
+ for k, v in iterator:
+ d[k] = comb(d[k], v) if k in d else v
+
+ def iteritems(self):
+ """ return the merged items ad iterator """
+ return self.data.iteritems()
+
+
+class ExternalMerger(Merger):
+
+ """
+ External merger will dump the aggregated data into disks when
+ memory usage goes above the limit, then merge them together.
+
+ This class works as follows:
+
+ - It repeatedly combine the items and save them in one dict in
+ memory.
+
+ - When the used memory goes above memory limit, it will split
+ the combined data into partitions by hash code, dump them
+ into disk, one file per partition.
+
+ - Then it goes through the rest of the iterator, combine items
+ into different dict by hash. Until the used memory goes over
+ memory limit, it dump all the dicts into disks, one file per
+ dict. Repeat this again until combine all the items.
+
+ - Before return any items, it will load each partition and
+ combine them seperately. Yield them before loading next
+ partition.
+
+ - During loading a partition, if the memory goes over limit,
+ it will partition the loaded data and dump them into disks
+ and load them partition by partition again.
+
+ >>> agg = Aggregator(lambda x: x, lambda x, y: x + y)
+ >>> merger = ExternalMerger(agg, 10)
+ >>> N = 10000
+ >>> merger.combine(zip(xrange(N), xrange(N)) * 10)
+ >>> assert merger.spills > 0
+ >>> sum(v for k,v in merger.iteritems())
+ 499950000
+
+ >>> merger = ExternalMerger(agg, 10)
+ >>> merger.merge(zip(xrange(N), xrange(N)) * 10)
+ >>> assert merger.spills > 0
+ >>> sum(v for k,v in merger.iteritems())
+ 499950000
+ """
+
+ PARTITIONS = 64 # number of partitions when spill data into disks
+ BATCH = 10000 # check the memory after # of items merged
+
+ def __init__(self, aggregator, memory_limit=512, serializer=None,
+ localdirs=None, scale=1):
+ Merger.__init__(self, aggregator)
+ self.memory_limit = memory_limit
+ # default serializer is only used for tests
+ self.serializer = serializer or \
+ BatchedSerializer(PickleSerializer(), 1024)
+ self.localdirs = localdirs or self._get_dirs()
+ # scale is used to scale down the hash of key for recursive hash
map,
+ self.scale = scale
+ # unpartitioned merged data
+ self.data = {}
+ # partitioned merged data
+ self.pdata = []
+ # number of chunks dumped into disks
+ self.spills = 0
+
+ def _get_dirs(self):
+ """ get all the directories """
+ path = os.environ.get("SPARK_LOCAL_DIR", "/tmp/spark")
+ dirs = path.split(",")
+ return [os.path.join(d, "python", str(os.getpid()), str(id(self)))
+ for d in dirs]
--- End diff --
Just so you know, our line length limit is 100 characters, not 80. You can
make some of these things one line.
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