Add a new option to enable signals

When running behind a wsgi server like apache/mod_wsgi, neutron should
not register on Signals, it will overlap with the Signals registered by
the wsgi server.

Related-Bug: #2021814

Change-Id: I3c74846a8337d019f1ab6759ebb03f18c3f00238
Signed-off-by: Arnaud Morin <arnaud.morin@ovhcloud.com>

neutron/conf/common.py

@@ -165,6 +165,10 @@ core_opts = [
                help=_('IPv6 address of this host. If no address is provided '
                       'and one cannot be determined, ::1 will be '
                       'used.')),
+    cfg.BoolOpt('enable_signals', default=True,
+                help=_('If False, neutron-server will not listen for signals '
+                       'like SIGINT or SIGTERM. This is useful when running '
+                       'behind a WSGI server like apache/mod_wsgi.')),
 ]
 
 core_cli_opts = [

neutron/plugins/ml2/ovo_rpc.py

@@ -154,9 +154,12 @@ class OVOServerRpcInterface(object):
     Generates RPC callback notifications on ML2 object changes.
     """
 
-    def __init__(self):
+    def __init__(self, enable_signals=True):
         self._rpc_pusher = resources_rpc.ResourcesPushRpcApi()
         self._setup_change_handlers()
+        # When running behind wsgi server (like apache2/mod_wsgi)
+        # we should not register signals
+        if enable_signals:
             _setup_change_handlers_cleanup()
         LOG.debug("ML2 OVO RPC backend initialized.")
 

neutron/plugins/ml2/plugin.py

@@ -407,7 +407,8 @@ class Ml2Plugin(db_base_plugin_v2.NeutronDbPluginV2,
         self.ovo_notifier = None
         rpc_workers = conf_service.get_rpc_workers()
         if rpc_workers is None or rpc_workers >= 1:
-            self.ovo_notifier = ovo_rpc.OVOServerRpcInterface()
+            self.ovo_notifier = ovo_rpc.OVOServerRpcInterface(
+                cfg.CONF.enable_signals)
         self.notifier = rpc.AgentNotifierApi(topics.AGENT)
         if cfg.CONF.enable_traditional_dhcp:
             self.agent_notifiers[const.AGENT_TYPE_DHCP] = (

releasenotes/notes/enable_signals-option-706167609c0a5fa7.yaml

@@ -0,0 +1,11 @@
+---
+features:
+  - |
+    A new config option ``enable_signals`` has been added to neutron.conf to
+    control whether neutron-server registers signal handlers or not (like
+    SIGTERM, etc). The default value for this new option is True to mimic the
+    original behavior of registering signal handlers.
+    The recommendation is to set this option to False when neutron-server is
+    running behind a WSGI server, because in that situation the signals are
+    taken over by the WSGI server and neutron will print a stack trace letting
+    us know that signals cannot be registered.