SERVER-47950 Continuous stepdown thread should fail resmoke job loudly on exceptions

(cherry picked from commit 116d80c8267425fb71043f5a1200993355917707)

2 files changed, 12 insertions, 8 deletions

diff --git a/buildscripts/resmokelib/testing/hooks/stepdown.py b/buildscripts/resmokelib/testing/hooks/stepdown.py
index f61d070037e..7f42118a14c 100644
--- a/buildscripts/resmokelib/testing/hooks/stepdown.py
+++ b/buildscripts/resmokelib/testing/hooks/stepdown.py
@@ -101,24 +101,16 @@ class ContinuousStepdown(interface.Hook):  # pylint: disable=too-many-instance-a
 
     def before_test(self, test, test_report):
         """Before test."""
-        self._check_thread()
         self.logger.info("Resuming the stepdown thread.")
         self._stepdown_thread.pause()
         self._stepdown_thread.resume()
 
     def after_test(self, test, test_report):
         """After test."""
-        self._check_thread()
         self.logger.info("Pausing the stepdown thread.")
         self._stepdown_thread.pause()
         self.logger.info("Paused the stepdown thread.")
 
-    def _check_thread(self):
-        if not self._stepdown_thread.is_alive():
-            msg = "The stepdown thread is not running."
-            self.logger.error(msg)
-            raise errors.ServerFailure(msg)
-
     def _add_fixture(self, fixture):
         if isinstance(fixture, replicaset.ReplicaSetFixture):
             if not fixture.all_nodes_electable:
@@ -419,6 +411,8 @@ class _StepdownThread(threading.Thread):  # pylint: disable=too-many-instance-at
             # Proactively log the exception when it happens so it will be
             # flushed immediately.
             self.logger.exception("Stepdown Thread threw exception")
+            # The event should be signaled whenever the thread is not performing stepdowns.
+            self._is_idle_evt.set()
 
     def stop(self):
         """Stop the thread."""
@@ -434,6 +428,8 @@ class _StepdownThread(threading.Thread):  # pylint: disable=too-many-instance-at
 
         # Wait until we are no longer executing stepdowns.
         self._is_idle_evt.wait()
+        # Check if the thread is alive in case it has thrown an exception while running.
+        self._check_thread()
         # Wait until we all the replica sets have primaries.
         self._await_primaries()
         # Wait for Mongos to retarget the primary for each shard and the config server.
@@ -463,6 +459,12 @@ class _StepdownThread(threading.Thread):  # pylint: disable=too-many-instance-at
         # Wait until stop or timeout.
         self._is_stopped_evt.wait(timeout)
 
+    def _check_thread(self):
+        if not self.is_alive():
+            msg = "The stepdown thread is not running."
+            self.logger.error(msg)
+            raise errors.ServerFailure(msg)
+
     def _await_primaries(self):
         for fixture in self._rs_fixtures:
             fixture.get_primary()
diff --git a/buildscripts/tests/resmokelib/testing/hooks/test_stepdown.py b/buildscripts/tests/resmokelib/testing/hooks/test_stepdown.py
index c700ab60bf7..32436a4e346 100644
--- a/buildscripts/tests/resmokelib/testing/hooks/test_stepdown.py
+++ b/buildscripts/tests/resmokelib/testing/hooks/test_stepdown.py
@@ -24,6 +24,8 @@ def _get_threading_lock(test_case, MockCondition):  # pylint: disable=invalid-na
 class TestStepdownThread(unittest.TestCase):
     @mock.patch("buildscripts.resmokelib.testing.fixtures.replicaset.ReplicaSetFixture")
     @mock.patch("buildscripts.resmokelib.testing.fixtures.shardedcluster.ShardedClusterFixture")
+    @mock.patch("buildscripts.resmokelib.testing.hooks.stepdown._StepdownThread.is_alive",
+                mock.Mock(return_value=True))
     def test_pause_throws_error(self, shardcluster_fixture, rs_fixture):
         stepdown_thread = _stepdown._StepdownThread(
             logger=logging.getLogger("hook_logger"),