/
single_partition_subscriber.py
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/
single_partition_subscriber.py
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import asyncio
from typing import Union, Dict, NamedTuple
import queue
from google.api_core.exceptions import FailedPrecondition, GoogleAPICallError
from google.cloud.pubsub_v1.subscriber.message import Message
from google.pubsub_v1 import PubsubMessage
from google.cloud.pubsublite.cloudpubsub.flow_control_settings import FlowControlSettings
from google.cloud.pubsublite.cloudpubsub.internal.ack_set_tracker import AckSetTracker
from google.cloud.pubsublite.cloudpubsub.message_transformer import MessageTransformer
from google.cloud.pubsublite.cloudpubsub.nack_handler import NackHandler
from google.cloud.pubsublite.cloudpubsub.subscriber import AsyncSubscriber
from google.cloud.pubsublite.internal.wire.permanent_failable import PermanentFailable
from google.cloud.pubsublite.internal.wire.subscriber import Subscriber
from google.cloud.pubsublite_v1 import FlowControlRequest, SequencedMessage
from google.cloud.pubsub_v1.subscriber._protocol import requests
class _SizedMessage(NamedTuple):
message: PubsubMessage
size_bytes: int
class SinglePartitionSubscriber(PermanentFailable, AsyncSubscriber):
_underlying: Subscriber
_flow_control_settings: FlowControlSettings
_ack_set_tracker: AckSetTracker
_nack_handler: NackHandler
_transformer: MessageTransformer
_queue: queue.Queue
_messages_by_offset: Dict[int, _SizedMessage]
_looper_future: asyncio.Future
def __init__(self, underlying: Subscriber, flow_control_settings: FlowControlSettings, ack_set_tracker: AckSetTracker,
nack_handler: NackHandler, transformer: MessageTransformer):
super().__init__()
self._underlying = underlying
self._flow_control_settings = flow_control_settings
self._ack_set_tracker = ack_set_tracker
self._nack_handler = nack_handler
self._transformer = transformer
self._queue = queue.Queue()
self._messages_by_offset = {}
async def read(self) -> Message:
message: SequencedMessage = await self.await_unless_failed(self._underlying.read())
try:
cps_message = self._transformer.transform(message)
offset = message.cursor.offset
self._ack_set_tracker.track(offset)
self._messages_by_offset[offset] = _SizedMessage(cps_message, message.size_bytes)
wrapped_message = Message(cps_message._pb, ack_id=str(offset), delivery_attempt=0, request_queue=self._queue)
return wrapped_message
except GoogleAPICallError as e:
self.fail(e)
raise e
async def _handle_ack(self, message: requests.AckRequest):
offset = int(message.ack_id)
await self._underlying.allow_flow(
FlowControlRequest(allowed_messages=1, allowed_bytes=self._messages_by_offset[offset].size_bytes))
del self._messages_by_offset[offset]
try:
await self._ack_set_tracker.ack(offset)
except GoogleAPICallError as e:
self.fail(e)
def _handle_nack(self, message: requests.NackRequest):
offset = int(message.ack_id)
sized_message = self._messages_by_offset[offset]
try:
# Put the ack request back into the queue since the callback may be called from another thread.
self._nack_handler.on_nack(sized_message.message,
lambda: self._queue.put(requests.AckRequest(
ack_id=message.ack_id,
byte_size=0, # Ignored
time_to_ack=0, # Ignored
ordering_key="" # Ignored
)))
except GoogleAPICallError as e:
self.fail(e)
async def _handle_queue_message(self, message: Union[
requests.AckRequest, requests.DropRequest, requests.ModAckRequest, requests.NackRequest]):
if isinstance(message, requests.DropRequest) or isinstance(message, requests.ModAckRequest):
self.fail(FailedPrecondition("Called internal method of google.cloud.pubsub_v1.subscriber.message.Message "
f"Pub/Sub Lite does not support: {message}"))
elif isinstance(message, requests.AckRequest):
await self._handle_ack(message)
else:
self._handle_nack(message)
async def _looper(self):
while True:
try:
# This is not an asyncio.Queue, and therefore we cannot do `await self._queue.get()`.
# A blocking wait would block the event loop, this needs to be a queue.Queue for
# compatibility with the Cloud Pub/Sub Message's requirements.
queue_message = self._queue.get_nowait()
await self._handle_queue_message(queue_message)
except queue.Empty:
await asyncio.sleep(.1)
async def __aenter__(self):
await self._ack_set_tracker.__aenter__()
await self._underlying.__aenter__()
self._looper_future = asyncio.ensure_future(self._looper())
await self._underlying.allow_flow(FlowControlRequest(
allowed_messages=self._flow_control_settings.messages_outstanding,
allowed_bytes=self._flow_control_settings.bytes_outstanding))
return self
async def __aexit__(self, exc_type, exc_value, traceback):
self._looper_future.cancel()
try:
await self._looper_future
except asyncio.CancelledError:
pass
await self._underlying.__aexit__(exc_type, exc_value, traceback)
await self._ack_set_tracker.__aexit__(exc_type, exc_value, traceback)