add looping call

glock/task.py

@@ -0,0 +1,60 @@
+# Copyright 2012 Johan Rydberg.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import logging
+import gevent
+
+log = logging.getLogger(__name__)
+
+
+class LoopingCall(object):
+    """Abstraction for calling a function within intervals."""
+
+    def __init__(self, clock, fn, *args, **kw):
+        self.clock = clock
+        self.fn = fn
+        self.args = args
+        self.kw = kw
+        self.greenlet = None
+        self.interval = 0
+        self.running = 0
+
+    def run(self):
+        """Loop over the function."""
+        try:
+            while self.running:
+                t0 = self.clock.time()
+                self.fn(*self.args, **self.kw)
+                t1 = self.clock.time()
+                dt = self.interval - (t1 - t0)
+                if dt > 0:
+                    self.clock.sleep(dt)
+        except Exception:
+            log.exception('caught exception in looping call')
+        finally:
+            self.running = 0
+
+    def start(self, interval, now=True):
+        """Start calling the function."""
+        self.running = 1
+        self.interval = interval
+        if now:
+            gevent.spawn(self.run)
+        else:
+            self.clock.call_later(self.interval, gevent.spawn,
+                    self.run)
+
+    def close(self):
+        """Stop calling the function."""
+        self.running = 0