Fixed broken process pool executor issue

Fixes #362.

apscheduler/executors/pool.py

@@ -1,4 +1,5 @@
 from abc import abstractmethod
+from concurrent.futures.process import BrokenProcessPool
 import concurrent.futures
 
 from apscheduler.executors.base import BaseExecutor, run_job
@@ -19,7 +20,13 @@ def callback(f):
             else:
                 self._run_job_success(job.id, f.result())
 
-        f = self._pool.submit(run_job, job, job._jobstore_alias, run_times, self._logger.name)
+        try:
+            f = self._pool.submit(run_job, job, job._jobstore_alias, run_times, self._logger.name)
+        except BrokenProcessPool:
+            self._logger.warning('Process pool is broken; replacing pool with a fresh instance')
+            self._pool = self._pool.__class__(self._pool._max_workers)
+            f = self._pool.submit(run_job, job, job._jobstore_alias, run_times, self._logger.name)
+
         f.add_done_callback(callback)
 
     def shutdown(self, wait=True):

docs/versionhistory.rst

@@ -29,6 +29,8 @@ APScheduler, see the :doc:`migration section <migration>`.
   one search condition
 * Fixed a problem where bound methods added as jobs via textual references were called with an
   unwanted extra ``self`` argument (PR by Pengjie Song)
+* Fixed ``BrokenPoolError`` in ``ProcessPoolExecutor`` so that it will automatically replace the
+  broken pool with a fresh instance
 
 
 3.6.3

tests/test_executors.py

@@ -2,14 +2,18 @@
 from threading import Event
 from types import TracebackType
 import gc
+import os
+import signal
 import time
 
 import pytest
 from pytz import UTC
 
-from apscheduler.events import EVENT_JOB_ERROR, EVENT_JOB_MISSED, EVENT_JOB_EXECUTED
+from apscheduler.events import EVENT_JOB_ERROR, EVENT_JOB_EXECUTED, EVENT_JOB_MISSED
 from apscheduler.executors.base import MaxInstancesReachedError, run_job
+from apscheduler.executors.pool import ProcessPoolExecutor
 from apscheduler.job import Job
+from apscheduler.schedulers.background import BackgroundScheduler
 from apscheduler.schedulers.base import BaseScheduler
 
 try:
@@ -144,3 +148,31 @@ def func():
 
     foos = [x for x in gc.get_objects() if type(x) is FooBar]
     assert len(foos) == 0
+
+
+def test_broken_pool():
+    def listener(evt):
+        nonlocal pid
+        pid = evt.retval
+        event.set()
+
+    pid = None
+    event = Event()
+    scheduler = BackgroundScheduler(executors={'default': ProcessPoolExecutor(1)})
+    scheduler.add_listener(listener, EVENT_JOB_EXECUTED)
+    scheduler.add_job(os.getpid, 'date', run_date=datetime.now(UTC))
+    scheduler.start()
+
+    event.wait(3)
+    killed_pid = pid
+    os.kill(pid, signal.SIGTERM)
+    try:
+        os.waitpid(pid, 0)
+    except OSError:
+        pass
+
+    event.clear()
+    scheduler.add_job(os.getpid, 'date', run_date=datetime.now(UTC))
+    event.wait(3)
+    assert pid != killed_pid
+    scheduler.shutdown(True)