Tidy up subscriber (#199)

- Define the message type
- Acknowledge callback after processing
- Consistent logger and altering levels
- Docstrings

pixl_core/src/core/patient_queue/subscriber.py

@@ -26,7 +26,7 @@
 
 from ._base import PixlBlockingInterface, PixlQueueInterface
 
-LOGGER = logging.getLogger(__name__)
+logger = logging.getLogger(__name__)
 
 
 class PixlConsumer(PixlQueueInterface):
@@ -61,25 +61,24 @@ async def run(self, callback: Callable[[Message], Awaitable[None]]) -> None:
                          be processed. Must take a dictionary and return None.
         """
         async with self._queue.iterator() as queue_iter:
+            # Pre-annotate the message type
+            message: aio_pika.abc.AbstractIncomingMessage
             async for message in queue_iter:
                 if not self.token_bucket.has_token:
                     await asyncio.sleep(0.01)
                     await message.reject(requeue=True)
                     continue
 
-                # Messages need to be acknowledged before a callback otherwise
-                # RabbitMQ can close the connection. As all messages that raise
-                # exceptions aren't returned to the queue we're safe to do this
-                await message.ack()
-
                 try:
                     await asyncio.sleep(0.01)  # Avoid very fast callbacks
                     await callback(deserialise(message.body))
                 except Exception:
-                    LOGGER.exception(
+                    logger.exception(
                         "Failed to process %s" "Not re-queuing message",
                         message.body.decode(),
                     )
+                finally:
+                    await message.ack()
 
     async def __aexit__(self, *args: object, **kwargs: Any) -> None:
         """Requirement for the asynchronous context manager"""
@@ -104,16 +103,17 @@ def consume_all(self, file_path: Path, timeout_in_seconds: int = 5) -> int:
         )
 
         def callback(method: Any, properties: Any, body: Any) -> None:  # noqa: ARG001
+            """Consume to file."""
             try:
                 with Path.open(file_path, "a") as csv_file:
                     print(str(body.decode()), file=csv_file)
             except:  # noqa: E722
-                LOGGER.debug("Failed to consume")
+                logger.exception("Failed to consume")
 
         counter = 0
         for args in generator:
             if all(arg is None for arg in args):
-                LOGGER.info("Stopping")
+                logger.info("Stopping")
                 break
             callback(*args)
             counter += 1