Issue #23051: multiprocessing.Pool methods imap() and imap_unordered() now
handle exceptions raised by an iterator. Patch by Alon Diamant and Davin
Potts.
diff --git a/Lib/multiprocessing/pool.py b/Lib/multiprocessing/pool.py
index 04531b9..991f87f 100644
--- a/Lib/multiprocessing/pool.py
+++ b/Lib/multiprocessing/pool.py
@@ -334,25 +334,34 @@
thread = threading.current_thread()
for taskseq, set_length in iter(taskqueue.get, None):
+ task = None
i = -1
- for i, task in enumerate(taskseq):
- if thread._state:
- debug('task handler found thread._state != RUN')
- break
- try:
- put(task)
- except Exception as e:
- job, ind = task[:2]
+ try:
+ for i, task in enumerate(taskseq):
+ if thread._state:
+ debug('task handler found thread._state != RUN')
+ break
try:
- cache[job]._set(ind, (False, e))
- except KeyError:
- pass
- else:
+ put(task)
+ except Exception as e:
+ job, ind = task[:2]
+ try:
+ cache[job]._set(ind, (False, e))
+ except KeyError:
+ pass
+ else:
+ if set_length:
+ debug('doing set_length()')
+ set_length(i+1)
+ continue
+ break
+ except Exception as ex:
+ job, ind = task[:2] if task else (0, 0)
+ if job in cache:
+ cache[job]._set(ind + 1, (False, ex))
if set_length:
debug('doing set_length()')
set_length(i+1)
- continue
- break
else:
debug('task handler got sentinel')
diff --git a/Lib/test/test_multiprocessing.py b/Lib/test/test_multiprocessing.py
index b1e75b5..681529f 100644
--- a/Lib/test/test_multiprocessing.py
+++ b/Lib/test/test_multiprocessing.py
@@ -1122,6 +1122,15 @@
def sqr(x, wait=0.0):
time.sleep(wait)
return x*x
+
+class SayWhenError(ValueError): pass
+
+def exception_throwing_generator(total, when):
+ for i in range(total):
+ if i == when:
+ raise SayWhenError("Somebody said when")
+ yield i
+
class _TestPool(BaseTestCase):
def test_apply(self):
@@ -1177,6 +1186,25 @@
self.assertEqual(it.next(), i*i)
self.assertRaises(StopIteration, it.next)
+ def test_imap_handle_iterable_exception(self):
+ if self.TYPE == 'manager':
+ self.skipTest('test not appropriate for {}'.format(self.TYPE))
+
+ it = self.pool.imap(sqr, exception_throwing_generator(10, 3), 1)
+ for i in range(3):
+ self.assertEqual(next(it), i*i)
+ self.assertRaises(SayWhenError, it.next)
+
+ # SayWhenError seen at start of problematic chunk's results
+ it = self.pool.imap(sqr, exception_throwing_generator(20, 7), 2)
+ for i in range(6):
+ self.assertEqual(next(it), i*i)
+ self.assertRaises(SayWhenError, it.next)
+ it = self.pool.imap(sqr, exception_throwing_generator(20, 7), 4)
+ for i in range(4):
+ self.assertEqual(next(it), i*i)
+ self.assertRaises(SayWhenError, it.next)
+
def test_imap_unordered(self):
it = self.pool.imap_unordered(sqr, range(1000))
self.assertEqual(sorted(it), map(sqr, range(1000)))
@@ -1184,6 +1212,25 @@
it = self.pool.imap_unordered(sqr, range(1000), chunksize=53)
self.assertEqual(sorted(it), map(sqr, range(1000)))
+ def test_imap_unordered_handle_iterable_exception(self):
+ if self.TYPE == 'manager':
+ self.skipTest('test not appropriate for {}'.format(self.TYPE))
+
+ it = self.pool.imap_unordered(sqr,
+ exception_throwing_generator(10, 3),
+ 1)
+ with self.assertRaises(SayWhenError):
+ # imap_unordered makes it difficult to anticipate the SayWhenError
+ for i in range(10):
+ self.assertEqual(next(it), i*i)
+
+ it = self.pool.imap_unordered(sqr,
+ exception_throwing_generator(20, 7),
+ 2)
+ with self.assertRaises(SayWhenError):
+ for i in range(20):
+ self.assertEqual(next(it), i*i)
+
def test_make_pool(self):
self.assertRaises(ValueError, multiprocessing.Pool, -1)
self.assertRaises(ValueError, multiprocessing.Pool, 0)
diff --git a/Misc/ACKS b/Misc/ACKS
index e91e2a4..752b83a 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -325,6 +325,7 @@
Caleb Deveraux
Catherine Devlin
Scott Dial
+Alon Diamant
Toby Dickenson
Mark Dickinson
Jack Diederich
diff --git a/Misc/NEWS b/Misc/NEWS
index 0be5fdb..a364f57 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -21,6 +21,10 @@
Library
-------
+- Issue #23051: multiprocessing.Pool methods imap() and imap_unordered() now
+ handle exceptions raised by an iterator. Patch by Alon Diamant and Davin
+ Potts.
+
- Issue #22928: Disabled HTTP header injections in httplib.
Original patch by Demian Brecht.