Copy LoopingCall from nova for service.py

Change-Id: Ib6683324f92345c17cfd7234d08070b48ffb4d3e
Signed-off-by: Angus Salkeld <asalkeld@redhat.com>

2 files changed, 140 insertions, 0 deletions

diff --git a/openstack/common/loopingcall.py b/openstack/common/loopingcall.py
new file mode 100644
index 0000000..ede3dae
--- /dev/null
+++ b/openstack/common/loopingcall.py
@@ -0,0 +1,88 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2010 United States Government as represented by the
+# Administrator of the National Aeronautics and Space Administration.
+# Copyright 2011 Justin Santa Barbara
+# All Rights Reserved.
+#
+#    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 sys
+
+from eventlet import event
+from eventlet import greenthread
+
+from openstack.common import log as logging
+from openstack.common.gettextutils import _
+
+LOG = logging.getLogger(__name__)
+
+
+class LoopingCallDone(Exception):
+    """Exception to break out and stop a LoopingCall.
+
+    The poll-function passed to LoopingCall can raise this exception to
+    break out of the loop normally. This is somewhat analogous to
+    StopIteration.
+
+    An optional return-value can be included as the argument to the exception;
+    this return-value will be returned by LoopingCall.wait()
+
+    """
+
+    def __init__(self, retvalue=True):
+        """:param retvalue: Value that LoopingCall.wait() should return."""
+        self.retvalue = retvalue
+
+
+class LoopingCall(object):
+    def __init__(self, f=None, *args, **kw):
+        self.args = args
+        self.kw = kw
+        self.f = f
+        self._running = False
+
+    def start(self, interval, initial_delay=None):
+        self._running = True
+        done = event.Event()
+
+        def _inner():
+            if initial_delay:
+                greenthread.sleep(initial_delay)
+
+            try:
+                while self._running:
+                    self.f(*self.args, **self.kw)
+                    if not self._running:
+                        break
+                    greenthread.sleep(interval)
+            except LoopingCallDone, e:
+                self.stop()
+                done.send(e.retvalue)
+            except Exception:
+                LOG.exception(_('in looping call'))
+                done.send_exception(*sys.exc_info())
+                return
+            else:
+                done.send(True)
+
+        self.done = done
+
+        greenthread.spawn(_inner)
+        return self.done
+
+    def stop(self):
+        self._running = False
+
+    def wait(self):
+        return self.done.wait()
diff --git a/tests/unit/test_loopingcall.py b/tests/unit/test_loopingcall.py
new file mode 100644
index 0000000..11aa7e3
--- /dev/null
+++ b/tests/unit/test_loopingcall.py
@@ -0,0 +1,52 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2012 Red Hat, Inc.
+#
+#    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 unittest
+
+from openstack.common import loopingcall
+
+
+class LoopingCallTestCase(unittest.TestCase):
+
+    def setUp(self):
+        self.num_runs = 0
+
+    def test_return_true(self):
+        def _raise_it():
+            raise loopingcall.LoopingCallDone(True)
+
+        timer = loopingcall.LoopingCall(_raise_it)
+        self.assertTrue(timer.start(interval=0.5).wait())
+
+    def test_return_false(self):
+        def _raise_it():
+            raise loopingcall.LoopingCallDone(False)
+
+        timer = loopingcall.LoopingCall(_raise_it)
+        self.assertFalse(timer.start(interval=0.5).wait())
+
+    def test_repeat(self):
+        self.num_runs = 2
+
+        def _wait_for_zero():
+            """Called at an interval until num_runs == 0."""
+            if self.num_runs == 0:
+                raise loopingcall.LoopingCallDone(False)
+            else:
+                self.num_runs = self.num_runs - 1
+
+        timer = loopingcall.LoopingCall(_wait_for_zero)
+        self.assertFalse(timer.start(interval=0.5).wait())