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fix: scheduler errors when executor in shutdown (#399)
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plamut committed May 18, 2021
1 parent e29a2c0 commit 39a83d3eef196e88478ad8362201a2ab12e9f681
Showing with 57 additions and 1 deletion.
  1. +11 −1 google/cloud/pubsub_v1/subscriber/scheduler.py
  2. +46 −0 tests/unit/pubsub_v1/subscriber/test_scheduler.py
@@ -21,6 +21,7 @@
import abc
import concurrent.futures
import queue
import warnings


class Scheduler(metaclass=abc.ABCMeta):
@@ -114,7 +115,14 @@ def schedule(self, callback, *args, **kwargs):
Returns:
None
"""
self._executor.submit(callback, *args, **kwargs)
try:
self._executor.submit(callback, *args, **kwargs)
except RuntimeError:
warnings.warn(
"Scheduling a callback after executor shutdown.",
category=RuntimeWarning,
stacklevel=2,
)

def shutdown(self, await_msg_callbacks=False):
"""Shut down the scheduler and immediately end all pending callbacks.
@@ -142,6 +150,8 @@ def shutdown(self, await_msg_callbacks=False):
try:
while True:
work_item = self._executor._work_queue.get(block=False)
if work_item is None: # Exceutor in shutdown mode.
continue
dropped_messages.append(work_item.args[0])
except queue.Empty:
pass
@@ -16,6 +16,7 @@
import queue
import threading
import time
import warnings

import mock

@@ -61,6 +62,24 @@ def callback(*args, **kwargs):
assert sorted(called_with) == expected_calls


def test_schedule_after_executor_shutdown_warning():
def callback(*args, **kwargs):
pass

scheduler_ = scheduler.ThreadScheduler()

scheduler_.schedule(callback, "arg1", kwarg1="meep")
scheduler_._executor.shutdown()

with warnings.catch_warnings(record=True) as warned:
scheduler_.schedule(callback, "arg2", kwarg2="boop")

assert len(warned) == 1
assert issubclass(warned[0].category, RuntimeWarning)
warning_msg = str(warned[0].message)
assert "after executor shutdown" in warning_msg


def test_shutdown_nonblocking_by_default():
called_with = []
at_least_one_called = threading.Event()
@@ -125,3 +144,30 @@ def callback(message):

err_msg = "Shutdown did not wait for the already running callbacks to complete."
assert at_least_one_completed.is_set(), err_msg


def test_shutdown_handles_executor_queue_sentinels():
at_least_one_called = threading.Event()

def callback(_):
at_least_one_called.set()
time.sleep(1.0)

executor = concurrent.futures.ThreadPoolExecutor(max_workers=1)
scheduler_ = scheduler.ThreadScheduler(executor=executor)

scheduler_.schedule(callback, "message_1")
scheduler_.schedule(callback, "message_2")
scheduler_.schedule(callback, "message_3")

# Simulate executor shutdown from another thread.
executor._work_queue.put(None)
executor._work_queue.put(None)

at_least_one_called.wait()
dropped = scheduler_.shutdown(await_msg_callbacks=True)

assert len(set(dropped)) == 2 # Also test for item uniqueness.
for msg in dropped:
assert msg is not None
assert msg.startswith("message_")

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