Bidirectional streaming for pubsub (async client)

dapr/aio/clients/grpc/client.py

@@ -24,7 +24,7 @@
 
 from warnings import warn
 
-from typing import Callable, Dict, Optional, Text, Union, Sequence, List, Any
+from typing import Callable, Dict, Optional, Text, Union, Sequence, List, Any, Awaitable
 from typing_extensions import Self
 
 from google.protobuf.message import Message as GrpcMessage
@@ -39,12 +39,14 @@
     AioRpcError,
 )
 
+from dapr.aio.clients.grpc.subscription import Subscription
 from dapr.clients.exceptions import DaprInternalError, DaprGrpcError
 from dapr.clients.grpc._crypto import EncryptOptions, DecryptOptions
 from dapr.clients.grpc._state import StateOptions, StateItem
 from dapr.clients.grpc._helpers import getWorkflowRuntimeStatus
 from dapr.clients.health import DaprHealth
 from dapr.clients.retry import RetryPolicy
+from dapr.common.pubsub.subscription import StreamInactiveError
 from dapr.conf.helpers import GrpcEndpoint
 from dapr.conf import settings
 from dapr.proto import api_v1, api_service_v1, common_v1
@@ -94,6 +96,7 @@
     UnlockResponse,
     GetWorkflowResponse,
     StartWorkflowResponse,
+    TopicEventResponse,
 )
 
 
@@ -482,6 +485,72 @@
 
         return DaprResponse(await call.initial_metadata())
 
+    async def subscribe(
+        self,
+        pubsub_name: str,
+        topic: str,
+        metadata: Optional[dict] = None,
+        dead_letter_topic: Optional[str] = None,
+    ) -> Subscription:
+        """
+        Subscribe to a topic with a bidirectional stream
+
+        Args:
+            pubsub_name (str): The name of the pubsub component.
+            topic (str): The name of the topic.
+            metadata (Optional[dict]): Additional metadata for the subscription.
+            dead_letter_topic (Optional[str]): Name of the dead-letter topic.
+
+        Returns:
+            Subscription: The Subscription object managing the stream.
+        """
+        subscription = Subscription(self._stub, pubsub_name, topic, metadata, dead_letter_topic)
+        await subscription.start()
+        return subscription
+
+    async def subscribe_with_handler(
+        self,
+        pubsub_name: str,
+        topic: str,
+        handler_fn: Callable[..., TopicEventResponse],
+        metadata: Optional[dict] = None,
+        dead_letter_topic: Optional[str] = None,
+    ) -> Callable[[], Awaitable[None]]:
+        """
+        Subscribe to a topic with a bidirectional stream and a message handler function
+
+        Args:
+            pubsub_name (str): The name of the pubsub component.
+            topic (str): The name of the topic.
+            handler_fn (Callable[..., TopicEventResponse]): The function to call when a message is received.
+            metadata (Optional[dict]): Additional metadata for the subscription.
+            dead_letter_topic (Optional[str]): Name of the dead-letter topic.
+
+        Returns:
+            Callable[[], Awaitable[None]]: An async function to close the subscription.
+        """
+        subscription = await self.subscribe(pubsub_name, topic, metadata, dead_letter_topic)
+
+        async def stream_messages(sub: Subscription):
+            while True:
+                try:
+                    message = await sub.next_message()
+                    if message:
+                        response = await handler_fn(message)
+                        if response:
+                            await subscription.respond(message, response.status)
+                    else:
+                        continue
+                except StreamInactiveError:
+                    break
+
+        async def close_subscription():
+            await subscription.close()
+
+        asyncio.create_task(stream_messages(subscription))
+
+        return close_subscription
+
     async def get_state(
         self,
         store_name: str,

dapr/aio/clients/grpc/interceptors.py

@@ -16,7 +16,7 @@
 from collections import namedtuple
 from typing import List, Tuple
 
-from grpc.aio import UnaryUnaryClientInterceptor, ClientCallDetails  # type: ignore
+from grpc.aio import UnaryUnaryClientInterceptor, StreamStreamClientInterceptor, ClientCallDetails  # type: ignore
 
 from dapr.conf import settings
 
@@ -51,7 +51,7 @@ def intercept_unary_unary(self, continuation, client_call_details, request):
         return continuation(client_call_details, request)
 
 
-class DaprClientInterceptorAsync(UnaryUnaryClientInterceptor):
+class DaprClientInterceptorAsync(UnaryUnaryClientInterceptor, StreamStreamClientInterceptor):
     """The class implements a UnaryUnaryClientInterceptor from grpc to add an interceptor to add
     additional headers to all calls as needed.
 
@@ -115,8 +115,24 @@ async def intercept_unary_unary(self, continuation, client_call_details, request
         Returns:
             A response object after invoking the continuation callable
         """
+        new_call_details = await self._intercept_call(client_call_details)
+        # Call continuation
+        response = await continuation(new_call_details, request)
+        return response
+
+    async def intercept_stream_stream(self, continuation, client_call_details, request):
+        """This method intercepts a stream-stream gRPC call. This is the implementation of the
+        abstract method defined in StreamStreamClientInterceptor defined in grpc. This is invoked
+        automatically by grpc based on the order in which interceptors are added to the channel.
+
+        Args:
+            continuation: a callable to be invoked to continue with the RPC or next interceptor
+            client_call_details: a ClientCallDetails object describing the outgoing RPC
+            request: the request value for the RPC
 
-        # Pre-process or intercept call
+        Returns:
+            A response object after invoking the continuation callable
+        """
         new_call_details = await self._intercept_call(client_call_details)
         # Call continuation
         response = await continuation(new_call_details, request)

dapr/aio/clients/grpc/subscription.py

@@ -0,0 +1,110 @@
+import asyncio
+from grpc import StatusCode
+from grpc.aio import AioRpcError
+
+from dapr.clients.grpc._response import TopicEventResponse
+from dapr.clients.health import DaprHealth
+from dapr.common.pubsub.subscription import StreamInactiveError, SubscriptionMessage
+from dapr.proto import api_v1, appcallback_v1
+
+
+class Subscription:
+    def __init__(self, stub, pubsub_name, topic, metadata=None, dead_letter_topic=None):
+        self._stub = stub
+        self._pubsub_name = pubsub_name
+        self._topic = topic
+        self._metadata = metadata or {}
+        self._dead_letter_topic = dead_letter_topic or ''
+        self._stream = None
+        self._send_queue = asyncio.Queue()
+        self._stream_active = asyncio.Event()
+
+    async def start(self):
+        async def outgoing_request_iterator():
+            try:
+                initial_request = api_v1.SubscribeTopicEventsRequestAlpha1(
+                    initial_request=api_v1.SubscribeTopicEventsRequestInitialAlpha1(
+                        pubsub_name=self._pubsub_name,
+                        topic=self._topic,
+                        metadata=self._metadata,
+                        dead_letter_topic=self._dead_letter_topic,
+                    )
+                )
+                yield initial_request
+
+                while self._stream_active.is_set():
+                    try:
+                        response = await asyncio.wait_for(self._send_queue.get(), timeout=1.0)
+                        yield response
+                    except asyncio.TimeoutError:
+                        continue
+            except Exception as e:
+                raise Exception(f'Error while writing to stream: {e}')
+
+        self._stream = self._stub.SubscribeTopicEventsAlpha1(outgoing_request_iterator())
+        self._stream_active.set()
+        await self._stream.read()  # discard the initial message
+
+    async def reconnect_stream(self):
+        await self.close()
+        DaprHealth.wait_until_ready()
+        print('Attempting to reconnect...')
+        await self.start()
+
+    async def next_message(self):
+        if not self._stream_active.is_set():
+            raise StreamInactiveError('Stream is not active')
+
+        try:
+            if self._stream is not None:
+                message = await self._stream.read()
+                if message is None:
+                    return None
+                return SubscriptionMessage(message.event_message)
+        except AioRpcError as e:
+            if e.code() == StatusCode.UNAVAILABLE:
+                print(
+                    f'gRPC error while reading from stream: {e.details()}, '
+                    f'Status Code: {e.code()}. '
+                    f'Attempting to reconnect...'
+                )
+                await self.reconnect_stream()
+            elif e.code() != StatusCode.CANCELLED:
+                raise Exception(f'gRPC error while reading from subscription stream: {e} ')
+        except Exception as e:
+            raise Exception(f'Error while fetching message: {e}')
+
+        return None
+
+    async def respond(self, message, status):
+        try:
+            status = appcallback_v1.TopicEventResponse(status=status.value)
+            response = api_v1.SubscribeTopicEventsRequestProcessedAlpha1(
+                id=message.id(), status=status
+            )
+            msg = api_v1.SubscribeTopicEventsRequestAlpha1(event_processed=response)
+            if not self._stream_active.is_set():
+                raise StreamInactiveError('Stream is not active')
+            await self._send_queue.put(msg)
+        except Exception as e:
+            print(f"Can't send message: {e}")
+
+    async def respond_success(self, message):
+        await self.respond(message, TopicEventResponse('success').status)
+
+    async def respond_retry(self, message):
+        await self.respond(message, TopicEventResponse('retry').status)
+
+    async def respond_drop(self, message):
+        await self.respond(message, TopicEventResponse('drop').status)
+
+    async def close(self):
+        if self._stream:
+            try:
+                self._stream.cancel()
+                self._stream_active.clear()
+            except AioRpcError as e:
+                if e.code() != StatusCode.CANCELLED:
+                    raise Exception(f'Error while closing stream: {e}')
+            except Exception as e:
+                raise Exception(f'Error while closing stream: {e}')

dapr/clients/grpc/client.py

@@ -12,7 +12,7 @@
 See the License for the specific language governing permissions and
 limitations under the License.
 """
-
+import threading
 import time
 import socket
 import json
@@ -41,6 +41,7 @@
 from dapr.clients.grpc._state import StateOptions, StateItem
 from dapr.clients.grpc._helpers import getWorkflowRuntimeStatus
 from dapr.clients.grpc._crypto import EncryptOptions, DecryptOptions
+from dapr.clients.grpc.subscription import Subscription, StreamInactiveError
 from dapr.clients.grpc.interceptors import DaprClientInterceptor, DaprClientTimeoutInterceptor
 from dapr.clients.health import DaprHealth
 from dapr.clients.retry import RetryPolicy
@@ -85,6 +86,7 @@
     StartWorkflowResponse,
     EncryptResponse,
     DecryptResponse,
+    TopicEventResponse,
 )
 
 
@@ -481,6 +483,78 @@ def publish_event(
 
         return DaprResponse(call.initial_metadata())
 
+    def subscribe(
+        self,
+        pubsub_name: str,
+        topic: str,
+        metadata: Optional[MetadataTuple] = None,
+        dead_letter_topic: Optional[str] = None,
+    ) -> Subscription:
+        """
+        Subscribe to a topic with a bidirectional stream
+
+        Args:
+            pubsub_name (str): The name of the pubsub component.
+            topic (str): The name of the topic.
+            metadata (Optional[MetadataTuple]): Additional metadata for the subscription.
+            dead_letter_topic (Optional[str]): Name of the dead-letter topic.
+            timeout (Optional[int]): The time in seconds to wait for a message before returning None
+                                     If not set, the `next_message` method will block indefinitely
+                                     until a message is received.
+
+        Returns:
+            Subscription: The Subscription object managing the stream.
+        """
+        subscription = Subscription(self._stub, pubsub_name, topic, metadata, dead_letter_topic)
+        subscription.start()
+        return subscription
+
+    def subscribe_with_handler(
+        self,
+        pubsub_name: str,
+        topic: str,
+        handler_fn: Callable[..., TopicEventResponse],
+        metadata: Optional[MetadataTuple] = None,
+        dead_letter_topic: Optional[str] = None,
+    ) -> Callable:
+        """
+        Subscribe to a topic with a bidirectional stream and a message handler function
+
+        Args:
+            pubsub_name (str): The name of the pubsub component.
+            topic (str): The name of the topic.
+            handler_fn (Callable[..., TopicEventResponse]): The function to call when a message is received.
+            metadata (Optional[MetadataTuple]): Additional metadata for the subscription.
+            dead_letter_topic (Optional[str]): Name of the dead-letter topic.
+            timeout (Optional[int]): The time in seconds to wait for a message before returning None
+                                     If not set, the `next_message` method will block indefinitely
+                                     until a message is received.
+        """
+        subscription = self.subscribe(pubsub_name, topic, metadata, dead_letter_topic)
+
+        def stream_messages(sub):
+            while True:
+                try:
+                    message = sub.next_message()
+                    if message:
+                        # Process the message
+                        response = handler_fn(message)
+                        if response:
+                            subscription.respond(message, response.status)
+                    else:
+                        # No message received
+                        continue
+                except StreamInactiveError:
+                    break
+
+        def close_subscription():
+            subscription.close()
+
+        streaming_thread = threading.Thread(target=stream_messages, args=(subscription,))
+        streaming_thread.start()
+
+        return close_subscription
+
     def get_state(
         self,
         store_name: str,