Use oslo_service's SignalHandler for signals

When Neutron is killed with SIGTERM (like via systemctl), when using
ML2/OVN neutron workers do not exit and instead are eventually killed
with SIGKILL when the graceful timeout is reached (often around 1
minute).

This is happening due to the signal handlers for SIGTERM. There are
multiple issues.

1) oslo_service, ml2/ovn mech_driver, and ml2/ovo_rpc.py all call
   signal.signal(signal.SIGTERM, ...) overwriting each others signal
   handlers.
2) SIGTERM is handled in the main thread, and running blocking code
   there causes AssertionErrors in eventlet which also prevents the
   process from exiting.
3) The ml2/ovn cleanup code doesn't cause the process to end, so it
   interrupts the killing of the process.

oslo_service has a singleton SignalHandler class that solves all of
these issues

Closes-Bug: #2056366
Change-Id: I730a12746bceaa744c658854e38439420efc4629
Signed-off-by: Terry Wilson <[email protected]>
(cherry picked from commit a4e49b6)
(cherry picked from commit 2a09a4b)

Author: otherwiseguy

neutron/plugins/ml2/drivers/ovn/mech_driver/mech_driver.py

@@ -19,7 +19,6 @@
 import functools
 import multiprocessing
 import operator
-import signal
 import threading
 import types
 import uuid
@@ -43,6 +42,7 @@
 from oslo_config import cfg
 from oslo_db import exception as os_db_exc
 from oslo_log import log
+from oslo_service import service as oslo_service
 from oslo_utils import timeutils
 from ovsdbapp.backend.ovs_idl import idlutils
 
@@ -312,8 +312,9 @@ def _setup_hash_ring(self):
         themselves to the hash ring.
         """
         # Attempt to remove the node from the ring when the worker stops
+        sh = oslo_service.SignalHandler()
         atexit.register(self._remove_node_from_hash_ring)
-        signal.signal(signal.SIGTERM, self._remove_node_from_hash_ring)
+        sh.add_handler("SIGTERM", self._remove_node_from_hash_ring)
 
         admin_context = n_context.get_admin_context()
         if not self._hash_ring_probe_event.is_set():

neutron/plugins/ml2/ovo_rpc.py

@@ -13,7 +13,6 @@
 
 import atexit
 import queue
-import signal
 import threading
 import traceback
 import weakref
@@ -24,6 +23,7 @@
 from neutron_lib import context as n_ctx
 from neutron_lib.db import api as db_api
 from oslo_log import log as logging
+from oslo_service import service
 
 from neutron.api.rpc.callbacks import events as rpc_events
 from neutron.api.rpc.handlers import resources_rpc
@@ -38,8 +38,9 @@
 
 def _setup_change_handlers_cleanup():
     atexit.register(_ObjectChangeHandler.clean_up)
-    signal.signal(signal.SIGINT, _ObjectChangeHandler.clean_up)
-    signal.signal(signal.SIGTERM, _ObjectChangeHandler.clean_up)
+    sh = service.SignalHandler()
+    sh.add_handler("SIGINT", _ObjectChangeHandler.clean_up)
+    sh.add_handler("SIGTERM", _ObjectChangeHandler.clean_up)
 
 
 class _ObjectChangeHandler(object):

requirements.txt

@@ -42,7 +42,7 @@ oslo.privsep>=2.3.0 # Apache-2.0
 oslo.reports>=1.18.0 # Apache-2.0
 oslo.rootwrap>=5.15.0 # Apache-2.0
 oslo.serialization>=2.25.0 # Apache-2.0
-oslo.service>=2.8.0 # Apache-2.0
+oslo.service>=3.1.2 # Apache-2.0
 oslo.upgradecheck>=1.3.0 # Apache-2.0
 oslo.utils>=4.8.0 # Apache-2.0
 oslo.versionedobjects>=1.35.1 # Apache-2.0