Import nova's looping call.

The looping call implementation had drifted in nova away from what
was in oslo. Update olso. I will move nova over to this code in a
later review.

Change-Id: I0e9214a150223dcd4fb1d695db36961bba794166

2 files changed, 59 insertions, 7 deletions

diff --git a/openstack/common/loopingcall.py b/openstack/common/loopingcall.py
index be044d8..3704e8e 100644
--- a/openstack/common/loopingcall.py
+++ b/openstack/common/loopingcall.py
@@ -46,12 +46,23 @@ class LoopingCallDone(Exception):
         self.retvalue = retvalue
 
 
-class LoopingCall(object):
+class LoopingCallBase(object):
     def __init__(self, f=None, *args, **kw):
         self.args = args
         self.kw = kw
         self.f = f
         self._running = False
+        self.done = None
+
+    def stop(self):
+        self._running = False
+
+    def wait(self):
+        return self.done.wait()
+
+
+class FixedIntervalLoopingCall(LoopingCallBase):
+    """A fixed interval looping call."""
 
     def start(self, interval, initial_delay=None):
         self._running = True
@@ -77,7 +88,7 @@ class LoopingCall(object):
                 self.stop()
                 done.send(e.retvalue)
             except Exception:
-                LOG.exception(_('in looping call'))
+                LOG.exception(_('in fixed duration looping call'))
                 done.send_exception(*sys.exc_info())
                 return
             else:
@@ -88,8 +99,49 @@ class LoopingCall(object):
         greenthread.spawn_n(_inner)
         return self.done
 
-    def stop(self):
-        self._running = False
 
-    def wait(self):
-        return self.done.wait()
+# TODO(mikal): this class name is deprecated in Havana and should be removed
+# in the I release
+LoopingCall = FixedIntervalLoopingCall
+
+
+class DynamicLoopingCall(LoopingCallBase):
+    """A looping call which sleeps until the next known event.
+
+    The function called should return how long to sleep for before being
+    called again.
+    """
+
+    def start(self, initial_delay=None, periodic_interval_max=None):
+        self._running = True
+        done = event.Event()
+
+        def _inner():
+            if initial_delay:
+                greenthread.sleep(initial_delay)
+
+            try:
+                while self._running:
+                    idle = self.f(*self.args, **self.kw)
+                    if not self._running:
+                        break
+
+                    if periodic_interval_max is not None:
+                        idle = min(idle, periodic_interval_max)
+                    LOG.debug(_('Dynamic looping call sleeping for %.02f '
+                                'seconds'), idle)
+                    greenthread.sleep(idle)
+            except LoopingCallDone, e:
+                self.stop()
+                done.send(e.retvalue)
+            except Exception:
+                LOG.exception(_('in dynamic looping call'))
+                done.send_exception(*sys.exc_info())
+                return
+            else:
+                done.send(True)
+
+        self.done = done
+
+        greenthread.spawn(_inner)
+        return self.done
diff --git a/openstack/common/threadgroup.py b/openstack/common/threadgroup.py
index a87497f..3558b73 100644
--- a/openstack/common/threadgroup.py
+++ b/openstack/common/threadgroup.py
@@ -63,7 +63,7 @@ class ThreadGroup(object):
 
     def add_timer(self, interval, callback, initial_delay=None,
                   *args, **kwargs):
-        pulse = loopingcall.LoopingCall(callback, *args, **kwargs)
+        pulse = loopingcall.FixedIntervalLoopingCall(callback, *args, **kwargs)
         pulse.start(interval=interval,
                     initial_delay=initial_delay)
         self.timers.append(pulse)