121 lines
3.6 KiB
Python
121 lines
3.6 KiB
Python
# Copyright 2021 The Matrix.org Foundation C.I.C.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import logging
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from typing import TYPE_CHECKING, Any, Optional
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from prometheus_client import Counter, Histogram
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from synapse.logging.context import make_deferred_yieldable
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from synapse.util import json_decoder, json_encoder
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if TYPE_CHECKING:
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from synapse.server import HomeServer
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set_counter = Counter(
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"synapse_external_cache_set",
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"Number of times we set a cache",
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labelnames=["cache_name"],
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)
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get_counter = Counter(
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"synapse_external_cache_get",
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"Number of times we get a cache",
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labelnames=["cache_name", "hit"],
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)
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response_timer = Histogram(
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"synapse_external_cache_response_time_seconds",
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"Time taken to get a response from Redis for a cache get/set request",
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labelnames=["method"],
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buckets=(
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0.001,
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0.002,
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0.005,
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0.01,
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0.02,
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0.05,
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),
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)
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logger = logging.getLogger(__name__)
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class ExternalCache:
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"""A cache backed by an external Redis. Does nothing if no Redis is
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configured.
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"""
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def __init__(self, hs: "HomeServer"):
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self._redis_connection = hs.get_outbound_redis_connection()
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def _get_redis_key(self, cache_name: str, key: str) -> str:
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return "cache_v1:%s:%s" % (cache_name, key)
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def is_enabled(self) -> bool:
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"""Whether the external cache is used or not.
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It's safe to use the cache when this returns false, the methods will
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just no-op, but the function is useful to avoid doing unnecessary work.
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"""
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return self._redis_connection is not None
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async def set(self, cache_name: str, key: str, value: Any, expiry_ms: int) -> None:
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"""Add the key/value to the named cache, with the expiry time given."""
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if self._redis_connection is None:
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return
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set_counter.labels(cache_name).inc()
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# txredisapi requires the value to be string, bytes or numbers, so we
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# encode stuff in JSON.
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encoded_value = json_encoder.encode(value)
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logger.debug("Caching %s %s: %r", cache_name, key, encoded_value)
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with response_timer.labels("set").time():
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return await make_deferred_yieldable(
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self._redis_connection.set(
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self._get_redis_key(cache_name, key),
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encoded_value,
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pexpire=expiry_ms,
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)
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)
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async def get(self, cache_name: str, key: str) -> Optional[Any]:
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"""Look up a key/value in the named cache."""
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if self._redis_connection is None:
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return None
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with response_timer.labels("get").time():
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result = await make_deferred_yieldable(
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self._redis_connection.get(self._get_redis_key(cache_name, key))
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)
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logger.debug("Got cache result %s %s: %r", cache_name, key, result)
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get_counter.labels(cache_name, result is not None).inc()
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if not result:
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return None
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# For some reason the integers get magically converted back to integers
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if isinstance(result, int):
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return result
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return json_decoder.decode(result)
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