From 4729ae47693e65e11f4635bceed6313e75d7c76f Mon Sep 17 00:00:00 2001
From: Min RK <benjaminrk@gmail.com>
Date: Wed, 3 Jan 2018 14:12:02 +0100
Subject: [PATCH] tornado 5 fixes

- ._running private attribute is removed. We don't need it anymore,
  since we were only using it while the application was run in a background thread.
- call blocking cleanup in a thread because asyncio doesn't allow multiple loops in one thread.
---
 jupyterhub/app.py           |  5 +----
 jupyterhub/tests/mocking.py | 23 +++++++++++++++++++----
 2 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/jupyterhub/app.py b/jupyterhub/app.py
index be3acff4..c74615d7 100644
--- a/jupyterhub/app.py
+++ b/jupyterhub/app.py
@@ -1625,10 +1625,7 @@ class JupyterHub(Application):
         if not self.io_loop:
             return
         if self.http_server:
-            if self.io_loop._running:
-                self.io_loop.add_callback(self.http_server.stop)
-            else:
-                self.http_server.stop()
+            self.http_server.stop()
         self.io_loop.add_callback(self.io_loop.stop)
 
     @gen.coroutine
diff --git a/jupyterhub/tests/mocking.py b/jupyterhub/tests/mocking.py
index 63f283b9..983fec08 100644
--- a/jupyterhub/tests/mocking.py
+++ b/jupyterhub/tests/mocking.py
@@ -1,5 +1,6 @@
 """mock utilities for testing"""
 
+from concurrent.futures import ThreadPoolExecutor
 import os
 import sys
 from tempfile import NamedTemporaryFile
@@ -202,11 +203,11 @@ class MockHub(JupyterHub):
     @default('authenticator_class')
     def _authenticator_class_default(self):
         return MockPAMAuthenticator
-    
+
     @default('spawner_class')
     def _spawner_class_default(self):
         return MockSpawner
-    
+
     def init_signal(self):
         pass
 
@@ -229,11 +230,25 @@ class MockHub(JupyterHub):
 
     def stop(self):
         super().stop()
-        IOLoop().run_sync(self.cleanup)
+
+        # run cleanup in a background thread
+        # to avoid multiple eventloops in the same thread errors from asyncio
+
+        def cleanup():
+            loop = IOLoop.current()
+            loop.run_sync(self.cleanup)
+            loop.close()
+
+        pool = ThreadPoolExecutor(1)
+        f = pool.submit(cleanup)
+        # wait for cleanup to finish
+        f.result()
+        pool.shutdown()
+
         # ignore the call that will fire in atexit
         self.cleanup = lambda : None
         self.db_file.close()
-    
+
     @gen.coroutine
     def login_user(self, name):
         """Login a user by name, returning her cookies."""