From 6566ec5e4b143f47a835223e5bcbe68766c52f7a Mon Sep 17 00:00:00 2001
From: Thomas Herve <therve@redhat.com>
Date: Fri, 19 Oct 2018 10:45:48 +0200
Subject: [PATCH] Use eventlet Event for loopingcall events

This fixes broken logic for finding out how to use green threads. Using
threading.Event with eventlet creates useless load related to timers.

Change-Id: I62e9f1a7cde8846be368fbec58b8e0825ce02079
Closes-Bug: #1798774
(cherry picked from commit c2463470f5e7edad1ffd369a472267d559590495)
---
 oslo_service/loopingcall.py            | 71 +++++++++-----------------
 oslo_service/tests/test_loopingcall.py |  3 --
 2 files changed, 24 insertions(+), 50 deletions(-)

diff --git a/oslo_service/loopingcall.py b/oslo_service/loopingcall.py
index 4bc67a2b..dc958040 100644
--- a/oslo_service/loopingcall.py
+++ b/oslo_service/loopingcall.py
@@ -17,13 +17,12 @@
 
 import random
 import sys
-import threading
 import time
 
 from eventlet import event
 from eventlet import greenthread
+from eventlet import timeout as eventlettimeout
 from oslo_log import log as logging
-from oslo_utils import eventletutils
 from oslo_utils import excutils
 from oslo_utils import reflection
 from oslo_utils import timeutils
@@ -77,51 +76,30 @@ def _safe_wrapper(f, kind, func_name):
     return func
 
 
-def _Event():
-    if eventletutils.is_monkey_patched('thread'):
-        return _ThreadingEvent()
-    else:
-        return _GreenEvent()
+class _Event(object):
+    """A class that provides consistent eventlet/threading Event API.
 
-
-class _ThreadingEvent(object):
-    def __init__(self):
-        self._abort = threading.Event()
-
-    def is_running(self):
-        return not self._abort.is_set()
+    It's a copy from the oslo_utils repository, as we need the private version
+    because we don't want to use the threading.Event version.
+    """
+    def __init__(self, *args, **kwargs):
+        self.clear()
 
     def clear(self):
-        self._abort.clear()
+        self._set = False
+        self._event = event.Event()
 
-    def wait(self, timeout):
-        self._abort.wait(timeout)
+    def is_set(self):
+        return self._set
 
-    def stop(self):
-        self._abort.set()
+    def set(self):
+        self._set = True
+        self._event.send(True)
 
-    def done(self):
-        pass
-
-
-class _GreenEvent(object):
-    def __init__(self):
-        self._running = False
-
-    def is_running(self):
-        return self._running
-
-    def clear(self):
-        self._running = True
-
-    def wait(self, timeout):
-        greenthread.sleep(timeout)
-
-    def stop(self):
-        self._running = False
-
-    def done(self):
-        self._running = False
+    def wait(self, timeout=None):
+        with eventlettimeout.Timeout(timeout, False):
+            self._event.wait()
+        return self.is_set()
 
 
 class LoopingCallBase(object):
@@ -136,25 +114,24 @@ class LoopingCallBase(object):
         self.f = f
         self._thread = None
         self.done = None
-        self._event = _Event()
+        self._abort = _Event()
 
     @property
     def _running(self):
-        return self._event.is_running()
+        return not self._abort.is_set()
 
     def stop(self):
         if self._running:
-            self._event.stop()
+            self._abort.set()
 
     def wait(self):
         return self.done.wait()
 
     def _on_done(self, gt, *args, **kwargs):
         self._thread = None
-        self._event.done()
 
     def _sleep(self, timeout):
-        self._event.wait(timeout)
+        self._abort.wait(timeout)
 
     def _start(self, idle_for, initial_delay=None, stop_on_exception=True):
         """Start the looping
@@ -172,7 +149,7 @@ class LoopingCallBase(object):
         if self._thread is not None:
             raise RuntimeError(self._RUN_ONLY_ONE_MESSAGE)
         self.done = event.Event()
-        self._event.clear()
+        self._abort.clear()
         self._thread = greenthread.spawn(
             self._run_loop, idle_for,
             initial_delay=initial_delay, stop_on_exception=stop_on_exception)
diff --git a/oslo_service/tests/test_loopingcall.py b/oslo_service/tests/test_loopingcall.py
index 82d495dd..35d05a1a 100644
--- a/oslo_service/tests/test_loopingcall.py
+++ b/oslo_service/tests/test_loopingcall.py
@@ -20,9 +20,6 @@ from oslotest import base as test_base
 import oslo_service
 from oslo_service import loopingcall
 
-threading = eventlet.patcher.original('threading')
-time = eventlet.patcher.original('time')
-
 
 class LoopingCallTestCase(test_base.BaseTestCase):