Nova api service doesn't handle SIGHUP properly

When SIGHUP signal is sent to nova-api service, it doesn't complete
processing of all pending requests before terminating all the
processes.

Closes-Bug: #1334647

Change-Id: I3f7bd0ba5ef1bb716a97635252abe251053a669d
(cherry picked from commit 224a3de)

nova/tests/test_wsgi.py

@@ -22,6 +22,7 @@
 
 import eventlet
 import eventlet.wsgi
+import mock
 import requests
 
 import nova.exception
@@ -126,6 +127,17 @@ def test_start_random_port_with_ipv6(self):
         server.stop()
         server.wait()
 
+    def test_server_pool_waitall(self):
+        # test pools waitall method gets called while stopping server
+        server = nova.wsgi.Server("test_server", None,
+            host="127.0.0.1", port=4444)
+        server.start()
+        with mock.patch.object(server._pool,
+                              'waitall') as mock_waitall:
+            server.stop()
+            server.wait()
+            mock_waitall.assert_called_once_with()
+
     def test_uri_length_limit(self):
         server = nova.wsgi.Server("test_uri_length_limit", None,
             host="127.0.0.1", max_url_len=16384)

nova/wsgi.py

@@ -237,6 +237,7 @@ def wait(self):
         """
         try:
             if self._server is not None:
+                self._pool.waitall()
                 self._server.wait()
         except greenlet.GreenletExit:
             LOG.info(_("WSGI server has stopped."))