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[SPARK-8202] [PYSPARK] fix infinite loop during external sort in PySpark #6714

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[SPARK-8202] [PYSPARK] fix infinite loop during external sort in PySpark #6714

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e746aec
fix batch size during sort
Jun 9, 2015
5c21777
Update shuffle.py
Jun 9, 2015
6ade745
update test
Jun 10, 2015
b9be832
Merge branch 'batch_size' of github.com:davies/spark into batch_size
Jun 10, 2015
b170dfb
update test
Jun 10, 2015
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5 changes: 1 addition & 4 deletions python/pyspark/shuffle.py
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Original file line number Diff line number Diff line change
Expand Up @@ -486,7 +486,7 @@ def sorted(self, iterator, key=None, reverse=False):
goes above the limit.
"""
global MemoryBytesSpilled, DiskBytesSpilled
batch, limit = 100, self.memory_limit
batch, limit = 100, self._next_limit()
chunks, current_chunk = [], []
iterator = iter(iterator)
while True:
Expand All @@ -512,9 +512,6 @@ def load(f):
f.close()
chunks.append(load(open(path, 'rb')))
current_chunk = []
gc.collect()
batch //= 2
limit = self._next_limit()
MemoryBytesSpilled += max(used_memory - get_used_memory(), 0) << 20
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@angelini angelini Jun 9, 2015

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Why is the call to gc.collect being removed?

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@davies davies Jun 9, 2015

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We won't change limit to _next_limit() (which call get_used_memory()). This line here was to get better number about how much memory was used, is not needed anymore.

DiskBytesSpilled += os.path.getsize(path)
os.unlink(path) # data will be deleted after close
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5 changes: 4 additions & 1 deletion python/pyspark/tests.py
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Expand Up @@ -179,9 +179,12 @@ def test_in_memory_sort(self):
list(sorter.sorted(l, key=lambda x: -x, reverse=True)))

def test_external_sort(self):
class CustomizedSorter(ExternalSorter):
def _next_limit(self):
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@JoshRosen JoshRosen Jun 18, 2015

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I think that we should add a comment here to explain why we're mocking out this part of the code; it doesn't seem self-evident to me and I'm worried that it's going to confuse future readers of this code.

Also, do you think that it's worth adding a separate test case for this path and keeping the old test? There might be some duplication of the code which does assertions over metrics, but we possibly can factor it out into a shared method.

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@JoshRosen JoshRosen Jun 18, 2015

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It seems like the intent here is to mock get_used_memory(); I'm not super familiar with Python mocking frameworks, but if this was Java then I imagine that get_used_memory() would be a method of some context / environment object that we could mock.

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@davies davies Jun 18, 2015

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Yes, without the mock, it will take a long time to reach memory limit (slowing down tests).

return self.memory_limit
l = list(range(1024))
random.shuffle(l)
sorter = ExternalSorter(1)
sorter = CustomizedSorter(1)
self.assertEqual(sorted(l), list(sorter.sorted(l)))
self.assertGreater(shuffle.DiskBytesSpilled, 0)
last = shuffle.DiskBytesSpilled
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