Controller event handling pipeline

This patch introduces ControllerPipeline which is an entry point
handler for the Kuryr-Kubernetes controller. ControllerPipeline
allows registering ResourceEventHandlers and ensures the proper
handler is called for each event that is passed to the
ControllerPipeline. Also it ensures the following behavior:

- multiple ResourceEventHandlers can be registered for the same
  resource type (OBJECT_KIND)

- failing handlers (i.e. ones that raise Exceptions) are retried
  until either the handler succeeds or a finite amount of time
  passes, in which case the most recent exception is logged

- in case there are multiple handlers registered for the same
  resource type, all such handlers are considered independent (i.e.
  if one handler fails, other handlers will still be called
  regardless; and the order in which such handlers are called is not
  determined)

- events for different Kubernetes objects can be handled concurrently

- events for the same Kubernetes object are handled sequentially in
  the order of arrival

Change-Id: Ib17e0c7a2790cdbc31be4f59d50972b43c272480
Partially-Implements: blueprint kuryr-k8s-integration

kuryr_kubernetes/controller/handlers/pipeline.py

@@ -0,0 +1,64 @@
+# Copyright (c) 2016 Mirantis, Inc.
+# 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.
+
+from oslo_log import log as logging
+
+from kuryr_kubernetes.handlers import asynchronous as h_async
+from kuryr_kubernetes.handlers import dispatch as h_dis
+from kuryr_kubernetes.handlers import k8s_base as h_k8s
+from kuryr_kubernetes.handlers import logging as h_log
+from kuryr_kubernetes.handlers import retry as h_retry
+
+LOG = logging.getLogger(__name__)
+
+
+class ControllerPipeline(h_dis.EventPipeline):
+    """Serves as an entry point for controller Kubernetes events.
+
+    `ControllerPipeline` is an entry point handler for the Kuryr-Kubernetes
+    controller. `ControllerPipeline` allows registering
+    :class:`kuryr_kubernetes.handlers.k8s_base.ResourceEventHandler`s and
+    ensures the proper handler is called for each event that is passed to the
+    `ControllerPipeline`. Also it ensures the following behavior:
+
+      - multiple `ResourceEventHandler`s can be registered for the same
+        resource type (`OBJECT_KIND`)
+
+      - failing handlers (i.e. ones that raise `Exception`s) are retried
+        until either the handler succeeds or a finite amount of time passes,
+        in which case the most recent exception is logged
+
+      - in case there are multiple handlers registered for the same resource
+        type, all such handlers are considered independent (i.e. if one
+        handler fails, other handlers will still be called regardless; and the
+        order in which such handlers are called is not determined)
+
+      - events for different Kubernetes objects can be handled concurrently
+
+      - events for the same Kubernetes object are handled sequentially in
+        the order of arrival
+    """
+
+    def __init__(self, thread_group):
+        self._tg = thread_group
+        super(ControllerPipeline, self).__init__()
+
+    def _wrap_consumer(self, consumer):
+        # TODO(ivc): tune retry interval/timeout
+        return h_log.LogExceptions(h_retry.Retry(consumer))
+
+    def _wrap_dispatcher(self, dispatcher):
+        return h_log.LogExceptions(h_async.Async(dispatcher, self._tg,
+                                                 h_k8s.object_uid))

kuryr_kubernetes/controller/service.py

@@ -22,10 +22,8 @@ from oslo_service import service
 from kuryr_kubernetes import clients
 from kuryr_kubernetes import config
 from kuryr_kubernetes import constants
-from kuryr_kubernetes.handlers import asynchronous as h_async
-from kuryr_kubernetes.handlers import dispatch as h_dis
+from kuryr_kubernetes.controller.handlers import pipeline as h_pipeline
 from kuryr_kubernetes.handlers import k8s_base as h_k8s
-from kuryr_kubernetes.handlers import retry as h_retry
 from kuryr_kubernetes import watcher
 
 LOG = logging.getLogger(__name__)
@@ -38,7 +36,7 @@ class KuryrK8sService(service.Service):
         super(KuryrK8sService, self).__init__()
 
         class DummyHandler(h_k8s.ResourceEventHandler):
-            OBJECT_KIND = constants.K8S_OBJ_NAMESPACE
+            # TODO(ivc): remove once real handlers are ready
 
             def __init__(self):
                 self.event_seq = 0
@@ -65,24 +63,23 @@ class KuryrK8sService(service.Service):
                 LOG.debug("present: %s",
                           event['object']['metadata']['selfLink'])
 
-        class DummyPipeline(h_dis.EventPipeline):
-            def __init__(self, thread_group):
-                self._tg = thread_group
-                super(DummyPipeline, self).__init__()
+        class DummyPodHandler(DummyHandler):
+            OBJECT_KIND = constants.K8S_OBJ_POD
 
-            def _wrap_consumer(self, consumer):
-                retry = h_retry.Retry(consumer)
-                return super(DummyPipeline, self)._wrap_consumer(retry)
+        class DummyServiceHandler(DummyHandler):
+            OBJECT_KIND = constants.K8S_OBJ_SERVICE
 
-            def _wrap_dispatcher(self, dispatcher):
-                handler = super(DummyPipeline, self)._wrap_dispatcher(
-                    dispatcher)
-                return h_async.Async(handler, self._tg, h_k8s.object_uid)
+        class DummyEndpointsHandler(DummyHandler):
+            OBJECT_KIND = constants.K8S_OBJ_ENDPOINTS
 
-        pipeline = DummyPipeline(self.tg)
-        pipeline.register(DummyHandler())
+        pipeline = h_pipeline.ControllerPipeline(self.tg)
         self.watcher = watcher.Watcher(pipeline, self.tg)
-        self.watcher.add(constants.K8S_API_NAMESPACES)
+        # TODO(ivc): pluggable resource/handler registration
+        for resource in ["pods", "services", "endpoints"]:
+            self.watcher.add("%s/%s" % (constants.K8S_API_BASE, resource))
+        pipeline.register(DummyPodHandler())
+        pipeline.register(DummyServiceHandler())
+        pipeline.register(DummyEndpointsHandler())
 
     def start(self):
         LOG.info(_LI("Service '%s' starting"), self.__class__.__name__)

kuryr_kubernetes/tests/unit/controller/handlers/test_pipeline.py

@@ -0,0 +1,60 @@
+# Copyright (c) 2016 Mirantis, Inc.
+# 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 mock
+
+from kuryr_kubernetes.controller.handlers import pipeline as h_pipeline
+from kuryr_kubernetes.handlers import dispatch as h_dis
+from kuryr_kubernetes.handlers import k8s_base as h_k8s
+from kuryr_kubernetes.tests import base as test_base
+
+
+class TestControllerPipeline(test_base.TestCase):
+    @mock.patch('kuryr_kubernetes.handlers.logging.LogExceptions')
+    @mock.patch('kuryr_kubernetes.handlers.retry.Retry')
+    def test_wrap_consumer(self, m_retry_type, m_logging_type):
+        consumer = mock.sentinel.consumer
+        retry_handler = mock.sentinel.retry_handler
+        logging_handler = mock.sentinel.logging_handler
+        m_retry_type.return_value = retry_handler
+        m_logging_type.return_value = logging_handler
+        thread_group = mock.sentinel.thread_group
+
+        with mock.patch.object(h_dis.EventPipeline, '__init__'):
+            pipeline = h_pipeline.ControllerPipeline(thread_group)
+            ret = pipeline._wrap_consumer(consumer)
+
+        self.assertEqual(logging_handler, ret)
+        m_logging_type.assert_called_with(retry_handler)
+        m_retry_type.assert_called_with(consumer)
+
+    @mock.patch('kuryr_kubernetes.handlers.logging.LogExceptions')
+    @mock.patch('kuryr_kubernetes.handlers.asynchronous.Async')
+    def test_wrap_dispatcher(self, m_async_type, m_logging_type):
+        dispatcher = mock.sentinel.dispatcher
+        async_handler = mock.sentinel.async_handler
+        logging_handler = mock.sentinel.logging_handler
+        m_async_type.return_value = async_handler
+        m_logging_type.return_value = logging_handler
+        thread_group = mock.sentinel.thread_group
+
+        with mock.patch.object(h_dis.EventPipeline, '__init__'):
+            pipeline = h_pipeline.ControllerPipeline(thread_group)
+            ret = pipeline._wrap_dispatcher(dispatcher)
+
+        self.assertEqual(logging_handler, ret)
+        m_logging_type.assert_called_with(async_handler)
+        m_async_type.assert_called_with(dispatcher, thread_group,
+                                        h_k8s.object_uid)