/
single_partition_subscriber.py
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/
single_partition_subscriber.py
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# Copyright 2020 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import asyncio
import json
from typing import Callable, 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.internal.wait_ignore_cancelled import wait_ignore_cancelled
from google.cloud.pubsublite.types 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.internal.single_subscriber import (
AsyncSingleSubscriber,
)
from google.cloud.pubsublite.internal.wire.permanent_failable import PermanentFailable
from google.cloud.pubsublite.internal.wire.subscriber import Subscriber
from google.cloud.pubsublite.internal.wire.subscriber_reset_handler import (
SubscriberResetHandler,
)
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 _AckId(NamedTuple):
generation: int
offset: int
def str(self) -> str:
return json.dumps({"generation": self.generation, "offset": self.offset})
@staticmethod
def parse(payload: str) -> "_AckId":
loaded = json.loads(payload)
return _AckId(
generation=int(loaded["generation"]), offset=int(loaded["offset"]),
)
ResettableSubscriberFactory = Callable[[SubscriberResetHandler], Subscriber]
class SinglePartitionSingleSubscriber(
PermanentFailable, AsyncSingleSubscriber, SubscriberResetHandler
):
_underlying: Subscriber
_flow_control_settings: FlowControlSettings
_ack_set_tracker: AckSetTracker
_nack_handler: NackHandler
_transformer: MessageTransformer
_queue: queue.Queue
_ack_generation_id: int
_messages_by_ack_id: Dict[str, _SizedMessage]
_looper_future: asyncio.Future
def __init__(
self,
subscriber_factory: ResettableSubscriberFactory,
flow_control_settings: FlowControlSettings,
ack_set_tracker: AckSetTracker,
nack_handler: NackHandler,
transformer: MessageTransformer,
):
super().__init__()
self._underlying = subscriber_factory(self)
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._ack_generation_id = 0
self._messages_by_ack_id = {}
async def handle_reset(self):
# Increment ack generation id to ignore unacked messages.
++self._ack_generation_id
await self._ack_set_tracker.clear_and_commit()
async def read(self) -> Message:
try:
message: SequencedMessage = await self.await_unless_failed(
self._underlying.read()
)
cps_message = self._transformer.transform(message)
offset = message.cursor.offset
ack_id = _AckId(self._ack_generation_id, offset)
self._ack_set_tracker.track(offset)
self._messages_by_ack_id[ack_id.str()] = _SizedMessage(
cps_message, message.size_bytes
)
wrapped_message = Message(
cps_message._pb,
ack_id=ack_id.str(),
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):
await self._underlying.allow_flow(
FlowControlRequest(
allowed_messages=1,
allowed_bytes=self._messages_by_ack_id[message.ack_id].size_bytes,
)
)
del self._messages_by_ack_id[message.ack_id]
# Always refill flow control tokens, but do not commit offsets from outdated generations.
ack_id = _AckId.parse(message.ack_id)
if ack_id.generation == self._ack_generation_id:
try:
await self._ack_set_tracker.ack(ack_id.offset)
except GoogleAPICallError as e:
self.fail(e)
def _handle_nack(self, message: requests.NackRequest):
sized_message = self._messages_by_ack_id[message.ack_id]
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(0.1)
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()
await wait_ignore_cancelled(self._looper_future)
await self._underlying.__aexit__(exc_type, exc_value, traceback)
await self._ack_set_tracker.__aexit__(exc_type, exc_value, traceback)