Add health check support to gRPC app (#723)

Signed-off-by: Yevgen Polyak <[email protected]>
Co-authored-by: Marc Duiker <[email protected]>
Co-authored-by: Bernd Verst <[email protected]>

.github/scripts/automerge.py

@@ -25,9 +25,8 @@
 
 def fetch_pulls(mergeable_state, labels={'automerge'}):
     return [pr for pr in repo.get_pulls(state='open', sort='created')
-            # noqa: E502
-            if (not pr.draft) and (pr.mergeable_state == mergeable_state) and \
-               (not labels or len(labels.intersection({label.name for label in pr.labels})) > 0)]
+            if (not pr.draft and pr.mergeable_state == mergeable_state
+                and (not labels or len(labels.intersection({label.name for label in pr.labels})) > 0))]
 
 
 def is_approved(pr):

examples/pubsub-simple/README.md

@@ -66,7 +66,7 @@ sleep: 15
 
 ```bash
 # 2. Start Publisher
-dapr run --app-id python-publisher --app-protocol grpc --dapr-grpc-port=3500 python3 publisher.py
+dapr run --app-id python-publisher --app-protocol grpc --dapr-grpc-port=3500 --enable-app-health-check python3 publisher.py
 ```
 
 <!-- END_STEP -->

examples/pubsub-simple/subscriber.py

@@ -83,4 +83,11 @@ def mytopic_wildcard(event: v1.Event) -> TopicEventResponse:
     return TopicEventResponse('success')
 
 
+# Example of an unhealthy status
+# def unhealthy():
+#     raise ValueError("Not healthy")
+# app.register_health_check(unhealthy)
+
+app.register_health_check(lambda: print('Healthy'))
+
 app.run(50051)

ext/dapr-ext-grpc/dapr/ext/grpc/_health_servicer.py

@@ -0,0 +1,32 @@
+import grpc
+from typing import Callable, Optional
+
+from dapr.proto import appcallback_service_v1
+from dapr.proto.runtime.v1.appcallback_pb2 import HealthCheckResponse
+
+HealthCheckCallable = Optional[Callable[[], None]]
+
+
+class _HealthCheckServicer(appcallback_service_v1.AppCallbackHealthCheckServicer):
+    """The implementation of HealthCheck Server.
+
+    :class:`App` provides useful decorators to register method, topic, input bindings.
+    """
+
+    def __init__(self):
+        self._health_check_cb: Optional[HealthCheckCallable] = None
+
+    def register_health_check(self, cb: HealthCheckCallable) -> None:
+        if not cb:
+            raise ValueError('health check callback must be defined')
+        self._health_check_cb = cb
+
+    def HealthCheck(self, request, context):
+        """Health check."""
+
+        if not self._health_check_cb:
+            context.set_code(grpc.StatusCode.UNIMPLEMENTED)  # type: ignore
+            context.set_details('Method not implemented!')
+            raise NotImplementedError('Method not implemented!')
+        self._health_check_cb()
+        return HealthCheckResponse()

ext/dapr-ext-grpc/dapr/ext/grpc/app.py

@@ -19,7 +19,8 @@
 from typing import Dict, Optional
 
 from dapr.conf import settings
-from dapr.ext.grpc._servicier import _CallbackServicer, Rule  # type: ignore
+from dapr.ext.grpc._servicer import _CallbackServicer, Rule  # type: ignore
+from dapr.ext.grpc._health_servicer import _HealthCheckServicer  # type: ignore
 from dapr.proto import appcallback_service_v1
 
 
@@ -43,6 +44,7 @@ def __init__(self, max_grpc_message_length: Optional[int] = None, **kwargs):
             kwargs: arguments to grpc.server()
         """
         self._servicer = _CallbackServicer()
+        self._health_check_servicer = _HealthCheckServicer()
         if not kwargs:
             options = []
             if max_grpc_message_length is not None:
@@ -56,6 +58,9 @@ def __init__(self, max_grpc_message_length: Optional[int] = None, **kwargs):
         else:
             self._server = grpc.server(**kwargs)  # type: ignore
         appcallback_service_v1.add_AppCallbackServicer_to_server(self._servicer, self._server)
+        appcallback_service_v1.add_AppCallbackHealthCheckServicer_to_server(
+            self._health_check_servicer, self._server
+        )
 
     def __del__(self):
         self.stop()
@@ -64,6 +69,15 @@ def add_external_service(self, servicer_callback, external_servicer):
         """Adds an external gRPC service to the same server"""
         servicer_callback(external_servicer, self._server)
 
+    def register_health_check(self, health_check_callback):
+        """Adds a health check callback
+
+        The below example adds a basic health check to check Dapr gRPC is running
+
+            @app.register_health_check(lambda: None)
+        """
+        self._health_check_servicer.register_health_check(health_check_callback)
+
     def run(self, app_port: Optional[int] = None, listen_address: Optional[str] = None) -> None:
         """Starts app gRPC server and waits until :class:`App`.stop() is called.
 

ext/dapr-ext-grpc/tests/test_app.py

@@ -74,3 +74,17 @@ def handle_dead_letter(event: v1.Event) -> None:
             'AppTests.test_subscribe_decorator.<locals>.handle_dead_letter',
             str(subscription_map['pubsub:topic2:']),
         )
+
+    def test_register_health_check(self):
+        def health_check_cb():
+            pass
+
+        self._app.register_health_check(health_check_cb)
+        registered_cb = self._app._health_check_servicer._health_check_cb
+        self.assertIn(
+            'AppTests.test_register_health_check.<locals>.health_check_cb', str(registered_cb)
+        )
+
+    def test_no_health_check(self):
+        registered_cb = self._app._health_check_servicer._health_check_cb
+        self.assertIsNone(registered_cb)

ext/dapr-ext-grpc/tests/test_health_servicer.py

@@ -0,0 +1,20 @@
+import unittest
+from unittest.mock import MagicMock
+
+from dapr.ext.grpc._health_servicer import _HealthCheckServicer
+
+
+class OnInvokeTests(unittest.TestCase):
+    def setUp(self):
+        self._health_servicer = _HealthCheckServicer()
+
+    def test_healthcheck_cb_called(self):
+        health_cb = MagicMock()
+        self._health_servicer.register_health_check(health_cb)
+        self._health_servicer.HealthCheck(None, MagicMock())
+        health_cb.assert_called_once()
+
+    def test_no_healthcheck_cb(self):
+        with self.assertRaises(NotImplementedError) as exception_context:
+            self._health_servicer.HealthCheck(None, MagicMock())
+        self.assertIn('Method not implemented!', exception_context.exception.args[0])

ext/dapr-ext-grpc/tests/test_servicier.py

@@ -19,18 +19,18 @@
 
 from dapr.clients.grpc._request import InvokeMethodRequest
 from dapr.clients.grpc._response import InvokeMethodResponse, TopicEventResponse
-from dapr.ext.grpc._servicier import _CallbackServicer
+from dapr.ext.grpc._servicer import _CallbackServicer
 from dapr.proto import common_v1, appcallback_v1
 
 from google.protobuf.any_pb2 import Any as GrpcAny
 
 
 class OnInvokeTests(unittest.TestCase):
     def setUp(self):
-        self._servicier = _CallbackServicer()
+        self._servicer = _CallbackServicer()
 
     def _on_invoke(self, method_name, method_cb):
-        self._servicier.register_method(method_name, method_cb)
+        self._servicer.register_method(method_name, method_cb)
 
         # fake context
         fake_context = MagicMock()
@@ -39,7 +39,7 @@ def _on_invoke(self, method_name, method_cb):
             ('key2', 'value1'),
         )
 
-        return self._servicier.OnInvoke(
+        return self._servicer.OnInvoke(
             common_v1.InvokeRequest(method=method_name, data=GrpcAny()),
             fake_context,
         )
@@ -93,18 +93,18 @@ def method_cb(request: InvokeMethodRequest):
 
 class TopicSubscriptionTests(unittest.TestCase):
     def setUp(self):
-        self._servicier = _CallbackServicer()
+        self._servicer = _CallbackServicer()
         self._topic1_method = Mock()
         self._topic2_method = Mock()
         self._topic3_method = Mock()
         self._topic3_method.return_value = TopicEventResponse('success')
         self._topic4_method = Mock()
 
-        self._servicier.register_topic('pubsub1', 'topic1', self._topic1_method, {'session': 'key'})
-        self._servicier.register_topic('pubsub1', 'topic3', self._topic3_method, {'session': 'key'})
-        self._servicier.register_topic('pubsub2', 'topic2', self._topic2_method, {'session': 'key'})
-        self._servicier.register_topic('pubsub2', 'topic3', self._topic3_method, {'session': 'key'})
-        self._servicier.register_topic(
+        self._servicer.register_topic('pubsub1', 'topic1', self._topic1_method, {'session': 'key'})
+        self._servicer.register_topic('pubsub1', 'topic3', self._topic3_method, {'session': 'key'})
+        self._servicer.register_topic('pubsub2', 'topic2', self._topic2_method, {'session': 'key'})
+        self._servicer.register_topic('pubsub2', 'topic3', self._topic3_method, {'session': 'key'})
+        self._servicer.register_topic(
             'pubsub3',
             'topic4',
             self._topic4_method,
@@ -121,12 +121,12 @@ def setUp(self):
 
     def test_duplicated_topic(self):
         with self.assertRaises(ValueError):
-            self._servicier.register_topic(
+            self._servicer.register_topic(
                 'pubsub1', 'topic1', self._topic1_method, {'session': 'key'}
             )
 
     def test_list_topic_subscription(self):
-        resp = self._servicier.ListTopicSubscriptions(None, None)
+        resp = self._servicer.ListTopicSubscriptions(None, None)
         self.assertEqual('pubsub1', resp.subscriptions[0].pubsub_name)
         self.assertEqual('topic1', resp.subscriptions[0].topic)
         self.assertEqual({'session': 'key'}, resp.subscriptions[0].metadata)
@@ -143,23 +143,23 @@ def test_list_topic_subscription(self):
         self.assertEqual({'session': 'key'}, resp.subscriptions[4].metadata)
 
     def test_topic_event(self):
-        self._servicier.OnTopicEvent(
+        self._servicer.OnTopicEvent(
             appcallback_v1.TopicEventRequest(pubsub_name='pubsub1', topic='topic1'),
             self.fake_context,
         )
 
         self._topic1_method.assert_called_once()
 
     def test_topic3_event_called_once(self):
-        self._servicier.OnTopicEvent(
+        self._servicer.OnTopicEvent(
             appcallback_v1.TopicEventRequest(pubsub_name='pubsub1', topic='topic3'),
             self.fake_context,
         )
 
         self._topic3_method.assert_called_once()
 
     def test_topic3_event_response(self):
-        response = self._servicier.OnTopicEvent(
+        response = self._servicer.OnTopicEvent(
             appcallback_v1.TopicEventRequest(pubsub_name='pubsub1', topic='topic3'),
             self.fake_context,
         )
@@ -169,7 +169,7 @@ def test_topic3_event_response(self):
         )
 
     def test_disable_topic_validation(self):
-        self._servicier.OnTopicEvent(
+        self._servicer.OnTopicEvent(
             appcallback_v1.TopicEventRequest(pubsub_name='pubsub3', topic='should_be_ignored'),
             self.fake_context,
         )
@@ -178,20 +178,20 @@ def test_disable_topic_validation(self):
 
     def test_non_registered_topic(self):
         with self.assertRaises(NotImplementedError):
-            self._servicier.OnTopicEvent(
+            self._servicer.OnTopicEvent(
                 appcallback_v1.TopicEventRequest(pubsub_name='pubsub1', topic='topic_non_existed'),
                 self.fake_context,
             )
 
 
 class BindingTests(unittest.TestCase):
     def setUp(self):
-        self._servicier = _CallbackServicer()
+        self._servicer = _CallbackServicer()
         self._binding1_method = Mock()
         self._binding2_method = Mock()
 
-        self._servicier.register_binding('binding1', self._binding1_method)
-        self._servicier.register_binding('binding2', self._binding2_method)
+        self._servicer.register_binding('binding1', self._binding1_method)
+        self._servicer.register_binding('binding2', self._binding2_method)
 
         # fake context
         self.fake_context = MagicMock()
@@ -202,15 +202,15 @@ def setUp(self):
 
     def test_duplicated_binding(self):
         with self.assertRaises(ValueError):
-            self._servicier.register_binding('binding1', self._binding1_method)
+            self._servicer.register_binding('binding1', self._binding1_method)
 
     def test_list_bindings(self):
-        resp = self._servicier.ListInputBindings(None, None)
+        resp = self._servicer.ListInputBindings(None, None)
         self.assertEqual('binding1', resp.bindings[0])
         self.assertEqual('binding2', resp.bindings[1])
 
     def test_binding_event(self):
-        self._servicier.OnBindingEvent(
+        self._servicer.OnBindingEvent(
             appcallback_v1.BindingEventRequest(name='binding1'),
             self.fake_context,
         )
@@ -219,7 +219,7 @@ def test_binding_event(self):
 
     def test_non_registered_binding(self):
         with self.assertRaises(NotImplementedError):
-            self._servicier.OnBindingEvent(
+            self._servicer.OnBindingEvent(
                 appcallback_v1.BindingEventRequest(name='binding3'),
                 self.fake_context,
             )