1 files changed, 53 insertions, 6 deletions
diff --git a/nova/utils.py b/nova/utils.py
index 26468868a..1056a6e2d 100644
--- a/nova/utils.py
+++ b/nova/utils.py
@@ -556,12 +556,23 @@ 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 looping call which happens at a fixed interval."""
 
     def start(self, interval, initial_delay=None):
         self._running = True
@@ -581,7 +592,7 @@ 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:
@@ -592,11 +603,47 @@ class LoopingCall(object):
         greenthread.spawn(_inner)
         return self.done
 
-    def stop(self):
-        self._running = False
 
-    def wait(self):
-        return self.done.wait()
+class DynamicLoopingCall(LoopingCallBase):
+    """A looping call which happens 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 not periodic_interval_max is None:
+                        idle = min(idle, periodic_interval_max)
+                    LOG.debug(_('Periodic task processor 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
 
 
 def xhtml_escape(value):