Fixed memory leak when scheduled jobs raise exceptions

Fixes #235.

3 files changed, 33 insertions, 1 deletions

diff --git a/apscheduler/executors/base.py b/apscheduler/executors/base.py
index a42768e..6ed1ec3 100644
--- a/apscheduler/executors/base.py
+++ b/apscheduler/executors/base.py
@@ -126,6 +126,16 @@ def run_job(job, jobstore_alias, run_times, logger_name):
         except BaseException:
             exc, tb = sys.exc_info()[1:]
             formatted_tb = ''.join(format_tb(tb))
+
+            # This is to prevent cyclic references that would lead to memory leaks
+            if six.PY2:
+                sys.exc_clear()
+                del tb
+            else:
+                import traceback
+                traceback.clear_frames(tb)
+                del tb
+
             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)
diff --git a/docs/versionhistory.rst b/docs/versionhistory.rst
index 66c09d3..8f54329 100644
--- a/docs/versionhistory.rst
+++ b/docs/versionhistory.rst
@@ -9,6 +9,9 @@ APScheduler, see the :doc:`migration section <migration>`.
 
 * Added the ``engine_options`` option to ``SQLAlchemyJobStore``
 
+* Fixed memory leak due to a cyclic reference when jobs raise exceptions
+  (thanks to gilbsgilbs for help on solving this)
+
 
 3.4.0
 -----
diff --git a/tests/test_executors.py b/tests/test_executors.py
index 2e90c17..d4aa221 100644
--- a/tests/test_executors.py
+++ b/tests/test_executors.py
@@ -1,12 +1,15 @@
 from datetime import datetime
 from threading import Event
 from types import TracebackType
+import gc
 import time
 
 import pytest
+from pytz import UTC
 
 from apscheduler.events import EVENT_JOB_ERROR, EVENT_JOB_MISSED, EVENT_JOB_EXECUTED
-from apscheduler.executors.base import MaxInstancesReachedError
+from apscheduler.executors.base import MaxInstancesReachedError, run_job
+from apscheduler.job import Job
 from apscheduler.schedulers.base import BaseScheduler
 
 try:
@@ -124,3 +127,19 @@ def test_run_job_error(monkeypatch, executor):
     assert str(exc_traceback[0]) == "dummy"
     if exc_traceback[1] is not None:
         assert isinstance(exc_traceback[1], TracebackType)
+
+
+def test_run_job_memory_leak():
+    class FooBar(object):
+        pass
+
+    def func():
+        foo = FooBar()  # noqa: F841
+        raise Exception('dummy')
+
+    fake_job = Mock(Job, func=func, args=(), kwargs={}, misfire_grace_time=1)
+    for _ in range(5):
+        run_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