sadpandajoe commented on code in PR #42760: URL: https://github.com/apache/superset/pull/42760#discussion_r4032894776
########## superset/semantic_layers/cache_coordination.py: ########## @@ -0,0 +1,207 @@ +# Licensed to the Apache Software Foundation (ASF) under one +# or more contributor license agreements. See the NOTICE file +# distributed with this work for additional information +# regarding copyright ownership. The ASF licenses this file +# to you 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. + +"""Ownership-safe coordination for semantic-cache descriptor mutations.""" + +import logging +import math +from collections.abc import Callable +from dataclasses import dataclass +from random import random +from threading import Event, Thread +from time import monotonic, sleep +from typing import Protocol, runtime_checkable +from uuid import uuid4 + +from redis.exceptions import RedisError + +from superset.semantic_layers.cache_repository import SemanticCacheCoordinationError + +SEMANTIC_CACHE_COORDINATION_FAILURE_METRIC: str = ( + "semantic_cache.containment.coordination_failure" +) +logger: logging.Logger = logging.getLogger(__name__) + + +@runtime_checkable +class OwnerTokenCoordinationBackend(Protocol): + """Atomic lease operations required from a coordination backend.""" + + def acquire_owner_token( + self, + key: str, + owner_token: str, + lease_seconds: int, + ) -> bool: ... # pragma: no cover + + def release_owner_token( + self, + key: str, + owner_token: str, + ) -> bool: ... # pragma: no cover + + def refresh_owner_token( + self, + key: str, + owner_token: str, + lease_seconds: int, + ) -> bool: ... # pragma: no cover + + +@dataclass(frozen=True) +class SemanticCacheCoordinationSettings: + """Validated bounded timing settings for descriptor leases.""" + + wait_seconds: float + lease_seconds: int + + def __post_init__(self) -> None: + if ( + isinstance(self.wait_seconds, bool) + or not isinstance(self.wait_seconds, (int, float)) + or not math.isfinite(self.wait_seconds) + or self.wait_seconds < 0 + ): + raise ValueError( + "Coordination wait seconds must be finite and non-negative" + ) + if ( + isinstance(self.lease_seconds, bool) + or not isinstance(self.lease_seconds, int) + or self.lease_seconds <= 0 + ): + raise ValueError("Coordination lease seconds must be positive") + + +class SemanticCacheCoordinator: + """Run descriptor mutations while holding an owner-token lease.""" + + def __init__( + self, + backend: OwnerTokenCoordinationBackend, + settings: SemanticCacheCoordinationSettings, + *, + clock: Callable[[], float] = monotonic, + sleeper: Callable[[float], None] = sleep, + token_factory: Callable[[], str] = lambda: uuid4().hex, + failure_metric: Callable[[str], None] | None = None, + jitter: Callable[[], float] = random, + ) -> None: + self._backend: OwnerTokenCoordinationBackend = backend + self._settings: SemanticCacheCoordinationSettings = settings + self._clock: Callable[[], float] = clock + self._sleeper: Callable[[float], None] = sleeper + self._token_factory: Callable[[], str] = token_factory + self._failure_metric: Callable[[str], None] = failure_metric or (lambda _: None) + self._jitter: Callable[[], float] = jitter + + def _failure(self, message: str, cause: RedisError | None = None) -> None: + self._record_failure() + error: SemanticCacheCoordinationError = SemanticCacheCoordinationError(message) + if cause is None: + raise error + raise error from cause + + def _record_failure(self) -> None: + try: + self._failure_metric(SEMANTIC_CACHE_COORDINATION_FAILURE_METRIC) + except Exception: # pylint: disable=broad-exception-caught + logger.debug("Semantic cache coordination metric failed", exc_info=True) + + def _run_with_renewal( + self, + lease_key: str, + owner_token: str, + operation: Callable[[], None], + ) -> bool: + renewal_stopped: Event = Event() + renewal_failed: Event = Event() + + def renew_lease() -> None: + interval: float = self._settings.lease_seconds / 3 + while not renewal_stopped.wait(interval): + try: + refreshed: bool = self._backend.refresh_owner_token( + lease_key, + owner_token, + self._settings.lease_seconds, + ) + except RedisError: + renewal_failed.set() + return + if not refreshed: + renewal_failed.set() + return + + renewal_thread: Thread = Thread( + target=renew_lease, + name="semantic-cache-lease-renewal", + daemon=True, + ) + renewal_thread.start() + try: + operation() Review Comment: Thanks for the clarification. The separate-client path still has the original stale-write race: `set_if_owner` returns `None`, then `cache_repository._set` refreshes the owner token and performs a plain data-cache `SET`. A forced refresh can take the coordination lease and write a newer value between those two calls, after which the paused writer still overwrites that value. Can the separate-store configuration fence the value write too, rather than documenting a race in the normal data-cache/coordination split? -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
