Fixed memory leak when coroutine jobs raise exceptions

Fixes #406. Closes #418.

3 files changed, 27 insertions, 1 deletions

diff --git a/apscheduler/executors/base_py3.py b/apscheduler/executors/base_py3.py
index 61abd84..7111d2a 100644
--- a/apscheduler/executors/base_py3.py
+++ b/apscheduler/executors/base_py3.py
@@ -1,5 +1,6 @@
 import logging
 import sys
+import traceback
 from datetime import datetime, timedelta
 from traceback import format_tb
 
@@ -33,6 +34,7 @@ async def run_coroutine_job(job, jobstore_alias, run_times, logger_name):
             events.append(JobExecutionEvent(EVENT_JOB_ERROR, job.id, jobstore_alias, run_time,
                                             exception=exc, traceback=formatted_tb))
             logger.exception('Job "%s" raised an exception', job)
+            traceback.clear_frames(tb)
         else:
             events.append(JobExecutionEvent(EVENT_JOB_EXECUTED, job.id, jobstore_alias, run_time,
                                             retval=retval))
diff --git a/docs/versionhistory.rst b/docs/versionhistory.rst
index 488adba..8c5d552 100644
--- a/docs/versionhistory.rst
+++ b/docs/versionhistory.rst
@@ -17,6 +17,7 @@ APScheduler, see the :doc:`migration section <migration>`.
 * Added PySide2 support (PR by Abdulla Ibrahim)
 * Fixed ``BlockingScheduler`` and ``BackgroundScheduler`` shutdown hanging after the user has
   erroneously tried to start it twice
+* Fixed memory leak when coroutine jobs raise exceptions (due to reference cycles in tracebacks)
 
 
 3.6.3
diff --git a/tests/test_executors_py35.py b/tests/test_executors_py35.py
index 7849eb0..ee66584 100644
--- a/tests/test_executors_py35.py
+++ b/tests/test_executors_py35.py
@@ -1,13 +1,18 @@
 """Contains test functions using Python 3.3+ syntax."""
+import gc
 from asyncio import CancelledError
 from datetime import datetime
+from unittest.mock import Mock, patch
 
 import pytest
+from pytz import utc
+
 from apscheduler.executors.asyncio import AsyncIOExecutor
+from apscheduler.executors.base_py3 import run_coroutine_job
 from apscheduler.executors.tornado import TornadoExecutor
+from apscheduler.job import Job
 from apscheduler.schedulers.asyncio import AsyncIOScheduler
 from apscheduler.schedulers.tornado import TornadoScheduler
-from pytz import utc
 
 
 @pytest.fixture
@@ -100,3 +105,21 @@ async def test_asyncio_executor_shutdown(asyncio_scheduler, asyncio_executor):
     asyncio_executor.shutdown()
     with pytest.raises(CancelledError):
         await futures.pop()
+
+
+@pytest.mark.asyncio
+async def test_run_job_memory_leak():
+    class FooBar:
+        pass
+
+    async def func():
+        foo = FooBar()  # noqa: F841
+        raise Exception('dummy')
+
+    fake_job = Mock(Job, func=func, args=(), kwargs={}, misfire_grace_time=1)
+    with patch('logging.getLogger'):
+        for _ in range(5):
+            await run_coroutine_job(fake_job, 'foo', [datetime.now(utc)], __name__)
+
+    foos = [x for x in gc.get_objects() if type(x) is FooBar]
+    assert len(foos) == 0