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https://github.com/suitenumerique/meet.git
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lebaudantoine
f74d23c57e
The previous presence cache lookup keyed off a scan over the whole cache, so its cost was O(db_size) rather than O(room_size). Combined with the recent switch to cursor-based `SCAN` at an inappropriate page size, this caused a lot of Redis round-trips and noticeably slowed down the backend pods under load. Refactor the presence cache to keep a per-room set of all its participant keys. Lookups now iterate that set instead of scanning the whole database. Complexity is now bounded by room size, not database size, which should restore the backend performance to its previous levels while keeping the lobby behavior unchanged.
80 lines
3.0 KiB
Python
80 lines
3.0 KiB
Python
"""Presence cache."""
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from typing import FrozenSet
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from uuid import UUID
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from django.conf import settings
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from django.core.cache import cache
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class PresenceCache:
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"""Store and invalidate (room, identity) presence entries."""
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@staticmethod
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def _get_cache_key(room_id: UUID | str, identity: str) -> str:
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"""Cache key for a (room, identity) presence entry."""
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return f"{settings.PRESENCE_KEY_PREFIX}_{room_id!s}_{identity}"
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@staticmethod
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def _get_index_key(room_id: UUID | str) -> str:
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"""Raw Redis key of the per-room identity index (a native SET).
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Built through django-redis' make_key so it lives under the same
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KEY_PREFIX/version namespace as the presence entries.
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"""
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return cache.client.make_key(
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f"{settings.PRESENCE_KEY_PREFIX}-index_{room_id!s}"
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)
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@staticmethod
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def _redis(write: bool = True):
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"""Raw redis-py client.
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SADD/SREM/SMEMBERS are not exposed by the Django cache API; this is
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the documented django-redis escape hatch.
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"""
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return cache.client.get_client(write=write)
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def _index_members(self, room_id: UUID | str) -> FrozenSet[str]:
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"""All identities currently indexed for the room."""
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members = self._redis(write=False).smembers(self._get_index_key(room_id))
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return frozenset(
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member.decode() if isinstance(member, bytes) else member
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for member in members
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)
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def is_marked_present(self, room_id: UUID | str, identity: str) -> bool:
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"""Return True if a positive presence entry exists in cache."""
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return bool(cache.get(self._get_cache_key(room_id, identity)))
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def mark_present(self, room_id: UUID | str, identity: str) -> None:
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"""Record that `identity` is in `room_id` and index it for the room."""
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cache.set(
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self._get_cache_key(room_id, identity),
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True,
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timeout=settings.PRESENCE_CACHE_TIMEOUT,
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)
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index_key = self._get_index_key(room_id)
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pipe = self._redis().pipeline(transaction=False)
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pipe.sadd(index_key, identity)
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pipe.expire(index_key, settings.PRESENCE_CACHE_TIMEOUT)
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pipe.execute()
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def clear(self, room_id: UUID | str, identity: str) -> None:
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"""Forget presence for one participant (e.g. on participant_left)."""
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cache.delete(self._get_cache_key(room_id, identity))
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self._redis().srem(self._get_index_key(room_id), identity)
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def clear_room(self, room_id: UUID | str) -> None:
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"""Forget presence for every participant of a room (on room_finished).
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Deletes the indexed entries and the index itself with targeted
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commands instead of a full-keyspace pattern scan.
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"""
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identities = self._index_members(room_id)
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if identities:
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cache.delete_many(
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[self._get_cache_key(room_id, identity) for identity in identities]
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)
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self._redis().delete(self._get_index_key(room_id))
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