From 13f2e1344a697c8c7adf795100e3e0ee92bdc43f Mon Sep 17 00:00:00 2001
From: Bernard Cafarelli <bcafarel@redhat.com>
Date: Fri, 7 Feb 2020 14:21:09 +0100
Subject: [PATCH] Re-use existing ProcessLauncher from wsgi in RPC workers

If both are run under the same process, and api_workers >= 2, the server
process will instantiate two oslo_service.ProcessLauncher instances

This should be avoided [0], and indeed causes issues on subprocess and
signal handling: killed RPC workers not respawning, SIGHUP on master
process leading to unresponsive server, signal not properly sent to all
child processes, ...

To avoid this, use the wsgi ProcessLauncher instance if it exists

[0] https://docs.openstack.org/oslo.service/latest/user/usage.html#launchers

Change-Id: Ic821f8ca84add9c8137ef712031afb43e491591c
Closes-Bug: #1780139
(cherry picked from commit 13aa00026f768642f385259ba7ccddcfdad3c75f)
---
 neutron/server/wsgi_eventlet.py |  2 +-
 neutron/service.py              | 17 +++++++++++------
 neutron/wsgi.py                 |  6 ++++++
 3 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/neutron/server/wsgi_eventlet.py b/neutron/server/wsgi_eventlet.py
index afd58bcca69..a2b3a342274 100644
--- a/neutron/server/wsgi_eventlet.py
+++ b/neutron/server/wsgi_eventlet.py
@@ -27,7 +27,7 @@ def eventlet_wsgi_server():
 
 def start_api_and_rpc_workers(neutron_api):
     try:
-        worker_launcher = service.start_all_workers()
+        worker_launcher = service.start_all_workers(neutron_api)
 
         pool = eventlet.GreenPool()
         api_thread = pool.spawn(neutron_api.wait)
diff --git a/neutron/service.py b/neutron/service.py
index 06bf4cdc7b2..0a5fafecd9d 100644
--- a/neutron/service.py
+++ b/neutron/service.py
@@ -243,7 +243,7 @@ class AllServicesNeutronWorker(neutron_worker.NeutronBaseWorker):
         self._launcher.restart()
 
 
-def _start_workers(workers):
+def _start_workers(workers, neutron_api=None):
     process_workers = [
         plugin_worker for plugin_worker in workers
         if plugin_worker.worker_process_count > 0
@@ -251,9 +251,14 @@ def _start_workers(workers):
 
     try:
         if process_workers:
-            worker_launcher = common_service.ProcessLauncher(
-                cfg.CONF, wait_interval=1.0, restart_method='mutate'
-            )
+            # Get eventual already existing instance from WSGI app
+            worker_launcher = None
+            if neutron_api:
+                worker_launcher = neutron_api.wsgi_app.process_launcher
+            if worker_launcher is None:
+                worker_launcher = common_service.ProcessLauncher(
+                    cfg.CONF, wait_interval=1.0, restart_method='mutate'
+                )
 
             # add extra process worker and spawn there all workers with
             # worker_process_count == 0
@@ -285,9 +290,9 @@ def _start_workers(workers):
                           'details.')
 
 
-def start_all_workers():
+def start_all_workers(neutron_api=None):
     workers = _get_rpc_workers() + _get_plugins_workers()
-    launcher = _start_workers(workers)
+    launcher = _start_workers(workers, neutron_api)
     registry.publish(resources.PROCESS, events.AFTER_SPAWN, None)
     return launcher
 
diff --git a/neutron/wsgi.py b/neutron/wsgi.py
index 8552b352c67..fd422835920 100644
--- a/neutron/wsgi.py
+++ b/neutron/wsgi.py
@@ -226,6 +226,12 @@ class Server(object):
                              log_format=CONF.wsgi_log_format,
                              socket_timeout=self.client_socket_timeout)
 
+    @property
+    def process_launcher(self):
+        if isinstance(self._server, common_service.ProcessLauncher):
+            return self._server
+        return None
+
 
 class Request(wsgi.Request):