[eventlet-removal] Remove the usage of eventlet from the OVN maintenance worker

Related-Bug: #2087953
Change-Id: I511e7f5dc0c8d92a376cd73819007270f2a915ca

doc/source/eventlet_deprecation/index.rst

@@ -134,6 +134,12 @@ The Neutron API consists of the following executables:
   mechanism driver.
 
 
+.. note::
+
+  Right now, only the API server and the OVN maintenance task are running
+  without eventlet.
+
+
 ML2/OVN
 ~~~~~~~
 
@@ -153,11 +159,20 @@ restarted, this method will provide the same register UUID and the previous
 register (if present in the database) will be overwritten.
 
 
+OVN maintenance task
+~~~~~~~~~~~~~~~~~~~~
+
+The ``OvnDbSynchronizer`` class now uses a ``threading.Thread`` to spawn the
+``do_sync`` function. This is used by the Northbound and Southbound
+synchronizer classes (``OvnNbSynchronizer``, ``OvnSbSynchronizer``).
+
+
 .. note::
 
-  Right now, only the API server is running without eventlet.
-
-
+  The ``stop`` method needs to be refactored, along with the function
+  ``do_sync`` implemented in each child class. The ``stop`` method needs to
+  support a fast exit mechanism to stop as fast as possible the running
+  synchronization.
 
 
 References

neutron/cmd/eventlet/server/__init__.py

@@ -11,7 +11,6 @@
 #    under the License.
 
 from neutron import server
-from neutron.server import ovn_maintenance
 from neutron.server import periodic_eventlet
 from neutron.server import rpc_eventlet
 from neutron.server import wsgi_eventlet
@@ -27,7 +26,3 @@ def main_rpc_eventlet():
 
 def main_periodic_eventlet():
     server.boot_server(periodic_eventlet.eventlet_periodic_workers)
-
-
-def main_ovn_maintenance_eventlet():
-    return server.boot_server(ovn_maintenance.eventlet_ovn_maintenance_worker)

neutron/cmd/server/__init__.py

@@ -13,9 +13,19 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-from neutron import server
-from neutron.server import api
+# NOTE(ralonsoh): remove once the default backend is ``BackendType.THREADING``
+import oslo_service.backend as service
+service.init_backend(service.BackendType.THREADING)
+
+# pylint: disable=wrong-import-position
+from neutron import server  # noqa: E402
+from neutron.server import api  # noqa: E402
+from neutron.server import ovn_maintenance  # noqa: E402
 
 
 def main_api_uwsgi():
     return server.boot_server(api.api_server)
+
+
+def main_ovn_maintenance():
+    return server.boot_server(ovn_maintenance.ovn_maintenance_worker)

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

@@ -13,8 +13,9 @@
 import abc
 from datetime import datetime
 import itertools
+import threading
+import time
 
-from eventlet import greenthread
 from neutron_lib.api.definitions import segment as segment_def
 from neutron_lib import constants
 from neutron_lib import context
@@ -47,17 +48,22 @@ class OvnDbSynchronizer(metaclass=abc.ABCMeta):
         self.ovn_driver = ovn_driver
         self.ovn_api = ovn_api
         self.core_plugin = core_plugin
+        self._thread = None
 
     def sync(self, delay_seconds=10):
-        self._gt = greenthread.spawn_after_local(delay_seconds, self.do_sync)
+        time.sleep(delay_seconds)
+        self._thread = threading.Thread(target=self.do_sync)
+        self._thread.start()
 
     @abc.abstractmethod
     def do_sync(self):
         """Method to sync the OVN DB."""
 
     def stop(self):
+        # TODO(ralonsoh): this method a the function executed in the thread
+        # should support a fast exit way.
         try:
-            self._gt.kill()
+            self._thread.join()
         except AttributeError:
             # Haven't started syncing
             pass

neutron/server/ovn_maintenance.py

@@ -24,8 +24,8 @@ from neutron import service
 LOG = log.getLogger(__name__)
 
 
-def eventlet_ovn_maintenance_worker():
-    LOG.info('Eventlet OVN maintenance process starting...')
+def ovn_maintenance_worker():
+    LOG.info('OVN maintenance process starting...')
 
     try:
         manager.init()

neutron/service.py

@@ -284,7 +284,7 @@ def _start_workers(workers, neutron_api=None):
                 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'
+                    cfg.CONF, restart_method='mutate',
                 )
 
             # add extra process worker and spawn there all workers with

setup.cfg

@@ -55,7 +55,7 @@ console_scripts =
     neutron-periodic-workers = neutron.cmd.eventlet.server:main_periodic_eventlet
     neutron-status = neutron.cmd.status:main
     neutron-ovn-agent = neutron.cmd.agents.ovn_neutron_agent:main
-    neutron-ovn-maintenance-worker = neutron.cmd.eventlet.server:main_ovn_maintenance_eventlet
+    neutron-ovn-maintenance-worker = neutron.cmd.server:main_ovn_maintenance
     neutron-ovn-metadata-agent = neutron.cmd.agents.ovn_metadata:main
     neutron-ovn-migration-mtu = neutron.cmd.ovn.migration_mtu:main
     neutron-ovn-db-sync-util = neutron.cmd.ovn.neutron_ovn_db_sync_util:main