OpenSlides/server/openslides/utils/consumer_autoupdate_strategy.py

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import asyncio
from asyncio import Task
from typing import Optional, cast
from django.conf import settings
from .autoupdate import get_autoupdate_data
from .cache import element_cache
from .websocket import ChangeIdTooHighException, ProtocollAsyncJsonWebsocketConsumer
AUTOUPDATE_DELAY = getattr(settings, "AUTOUPDATE_DELAY", None)
class ConsumerAutoupdateStrategy:
def __init__(self, consumer: ProtocollAsyncJsonWebsocketConsumer) -> None:
self.consumer = consumer
# client_change_id = None: unknown -> set on first autoupdate or request_change_id
# client_change_id is int: the change_id, the client knows about, so the next
# update must be from client_change_id+1 .. <next clange_id>
self.client_change_id: Optional[int] = None
self.next_send_time = None
self.timer_task_handle: Optional[Task[None]] = None
self.lock = asyncio.Lock()
async def request_change_id(
self, change_id: int, in_response: Optional[str] = None
) -> None:
"""
The change id is not inclusive, so the client is on change_id and wants
data from change_id+1 .. now
"""
# This resets the server side tracking of the client's change id.
async with self.lock:
await self.stop_timer()
max_change_id = await element_cache.get_current_change_id()
self.client_change_id = change_id
if self.client_change_id == max_change_id:
# The client is up-to-date, so nothing will be done
return None
if self.client_change_id > max_change_id:
message = (
f"Requested change_id {self.client_change_id} is higher than the "
+ f"highest change_id {max_change_id}."
)
raise ChangeIdTooHighException(message, in_response=in_response)
await self.send_autoupdate(in_response=in_response)
async def new_change_id(self, change_id: int) -> None:
async with self.lock:
if self.client_change_id is None:
# The -1 is to send this autoupdate as the first one to he client.
# Remember: the client_change_id is the change_id the client knows about
self.client_change_id = change_id - 1
if AUTOUPDATE_DELAY is None: # feature deactivated, send directly
await self.send_autoupdate()
elif self.timer_task_handle is None:
await self.start_timer()
async def get_running_loop(self) -> asyncio.AbstractEventLoop:
if hasattr(asyncio, "get_running_loop"):
return asyncio.get_running_loop() # type: ignore
else:
return asyncio.get_event_loop()
async def start_timer(self) -> None:
loop = await self.get_running_loop()
self.timer_task_handle = loop.create_task(self.timer_task())
async def stop_timer(self) -> None:
if self.timer_task_handle is not None:
self.timer_task_handle.cancel()
self.timer_task_handle = None
async def timer_task(self) -> None:
try:
await asyncio.sleep(AUTOUPDATE_DELAY)
except asyncio.CancelledError:
return
async with self.lock:
await self.send_autoupdate()
self.timer_task_handle = None
async def send_autoupdate(self, in_response: Optional[str] = None) -> None:
# here, 1 is added to the change_id, because the client_change_id is the id the client
# *knows* about -> the client needs client_change_id+1 since get_autoupdate_data is
# inclusive [change_id .. max_change_id].
max_change_id, autoupdate = await get_autoupdate_data(
cast(int, self.client_change_id) + 1, self.consumer.user_id
)
if autoupdate is not None:
self.client_change_id = max_change_id
# It will be send, so we can set the client_change_id
await self.consumer.send_json(
type="autoupdate", content=autoupdate, in_response=in_response,
)