asfgit closed pull request #23470: [SPARK-26549][PySpark] Fix for python worker
reuse take no effect for parallelize lazy iterable range
URL: https://github.com/apache/spark/pull/23470
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diff --git a/python/pyspark/context.py b/python/pyspark/context.py
index 6137ed25a0dd9..180a3e882dab6 100644
--- a/python/pyspark/context.py
+++ b/python/pyspark/context.py
@@ -493,6 +493,14 @@ def getStart(split):
return start0 + int((split * size / numSlices)) * step
def f(split, iterator):
+ # it's an empty iterator here but we need this line for
triggering the
+ # logic of signal handling in FramedSerializer.load_stream,
for instance,
+ # SpecialLengths.END_OF_DATA_SECTION in _read_with_length.
Since
+ # FramedSerializer.load_stream produces a generator, the
control should
+ # at least be in that function once. Here we do it by
explicitly converting
+ # the empty iterator to a list, thus make sure worker reuse
takes effect.
+ # See more details in SPARK-26549.
+ assert len(list(iterator)) == 0
return xrange(getStart(split), getStart(split + 1), step)
return self.parallelize([], numSlices).mapPartitionsWithIndex(f)
diff --git a/python/pyspark/tests/test_worker.py
b/python/pyspark/tests/test_worker.py
index a33b77d983419..a4f108f18e17d 100644
--- a/python/pyspark/tests/test_worker.py
+++ b/python/pyspark/tests/test_worker.py
@@ -22,7 +22,7 @@
from py4j.protocol import Py4JJavaError
-from pyspark.testing.utils import ReusedPySparkTestCase, QuietTest
+from pyspark.testing.utils import ReusedPySparkTestCase, PySparkTestCase,
QuietTest
if sys.version_info[0] >= 3:
xrange = range
@@ -145,6 +145,16 @@ def test_with_different_versions_of_python(self):
self.sc.pythonVer = version
+class WorkerReuseTest(PySparkTestCase):
+
+ def test_reuse_worker_of_parallelize_xrange(self):
+ rdd = self.sc.parallelize(xrange(20), 8)
+ previous_pids = rdd.map(lambda x: os.getpid()).collect()
+ current_pids = rdd.map(lambda x: os.getpid()).collect()
+ for pid in current_pids:
+ self.assertTrue(pid in previous_pids)
+
+
if __name__ == "__main__":
import unittest
from pyspark.tests.test_worker import *
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