init comment-service

services/comment-service/comment_service/events/producer.py

@@ -0,0 +1,89 @@
+import asyncio
+
+from aiokafka import AIOKafkaProducer
+
+from comment_service.models.config import Config
+from comment_service.models.service import Comment
+from comment_service.models.proto import comment_pb2
+
+
+class CommentEventProducer:
+    """Service event producer.
+    
+    Attributes:
+        _producer (aiokafka.AIOKafkaProducer): The underlying Kafka instance.
+        _pending_sends (set): Background events that are still awaiting a response.
+        
+    """
+    def __init__(self, config: Config) -> None:
+        """Initialise the event producer.
+        
+        Args:
+            config (Config): The app configuration instance (to access Kafka brokers list).
+
+        """
+        self._producer = AIOKafkaProducer(
+            bootstrap_servers=config.kafka_brokers,
+            client_id="auth-service"
+        )
+        self._pending_sends = set()
+
+    async def start(self) -> None:
+        """Start the underlying Kafka instance (open a connection)."""
+        await self._producer.start()
+
+    async def _send_event(self, event: comment_pb2.CommentEvent) -> None:
+        """Send an event.
+        
+        Execute the sending action as a background task to avoid
+        delaying a response to the request.
+
+        Args:
+            event (comment_pb2.CommentEvent): The protobuf class for the event.
+
+        """
+        bg_task = asyncio.create_task(self._producer.send(
+            topic="comment",
+            value=event.SerializeToString(),
+        ))
+        self._pending_sends.add(bg_task)
+        bg_task.add_done_callback(self._pending_sends.discard)
+
+    async def send_created_event(self, comment: Comment) -> None:
+        """Send a comment created event.
+        
+        Args:
+            comment (Comment): The comment to reference.
+        
+        """
+        event = comment_pb2.CommentEvent(
+            type="created",
+            data=Comment.to_protobuf(comment)
+        )
+        await self._send_event(event)
+
+    async def send_updated_event(self, comment: Comment) -> None:
+        """Send a comment updated event.
+        
+        Args:
+            comment (Comment): The comment to reference.
+        
+        """
+        event = comment_pb2.CommentEvent(
+            type="updated",
+            data=Comment.to_protobuf(comment)
+        )
+        await self._send_event(event)
+
+    async def send_deleted_event(self, comment: Comment) -> None:
+        """Send a comment deleted event.
+        
+        Args:
+            comment (Comment): The comment to reference.
+        
+        """
+        event = comment_pb2.CommentEvent(
+            type="deleted",
+            data=Comment.to_protobuf(comment)
+        )
+        await self._send_event(event)