Add DeferredCache.get_immediate method (#8568)

* Add `DeferredCache.get_immediate` method

A bunch of things that are currently calling `DeferredCache.get` are only
really interested in the result if it's completed. We can optimise and simplify
this case.

* Remove unused 'default' parameter to DeferredCache.get()

* another get_immediate instance
This commit is contained in:
Richard van der Hoff 2020-10-19 15:00:12 +01:00 committed by GitHub
parent c356b4bf42
commit 903d11c43a
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7 changed files with 53 additions and 27 deletions

1
changelog.d/8568.misc Normal file
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@ -0,0 +1 @@
Add `get_immediate` method to `DeferredCache`.

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@ -496,6 +496,6 @@ class _Invalidation(namedtuple("_Invalidation", ("cache", "room_id"))):
# dedupe when we add callbacks to lru cache nodes, otherwise the number # dedupe when we add callbacks to lru cache nodes, otherwise the number
# of callbacks would grow. # of callbacks would grow.
def __call__(self): def __call__(self):
rules = self.cache.get(self.room_id, None, update_metrics=False) rules = self.cache.get_immediate(self.room_id, None, update_metrics=False)
if rules: if rules:
rules.invalidate_all() rules.invalidate_all()

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@ -303,7 +303,7 @@ class PusherStore(PusherWorkerStore):
lock=False, lock=False,
) )
user_has_pusher = self.get_if_user_has_pusher.cache.get( user_has_pusher = self.get_if_user_has_pusher.cache.get_immediate(
(user_id,), None, update_metrics=False (user_id,), None, update_metrics=False
) )

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@ -25,7 +25,6 @@ from synapse.storage.database import DatabasePool
from synapse.storage.util.id_generators import StreamIdGenerator from synapse.storage.util.id_generators import StreamIdGenerator
from synapse.types import JsonDict from synapse.types import JsonDict
from synapse.util import json_encoder from synapse.util import json_encoder
from synapse.util.async_helpers import ObservableDeferred
from synapse.util.caches.descriptors import cached, cachedList from synapse.util.caches.descriptors import cached, cachedList
from synapse.util.caches.stream_change_cache import StreamChangeCache from synapse.util.caches.stream_change_cache import StreamChangeCache
@ -413,18 +412,10 @@ class ReceiptsWorkerStore(SQLBaseStore, metaclass=abc.ABCMeta):
if receipt_type != "m.read": if receipt_type != "m.read":
return return
# Returns either an ObservableDeferred or the raw result res = self.get_users_with_read_receipts_in_room.cache.get_immediate(
res = self.get_users_with_read_receipts_in_room.cache.get(
room_id, None, update_metrics=False room_id, None, update_metrics=False
) )
# first handle the ObservableDeferred case
if isinstance(res, ObservableDeferred):
if res.has_called():
res = res.get_result()
else:
res = None
if res and user_id in res: if res and user_id in res:
# We'd only be adding to the set, so no point invalidating if the # We'd only be adding to the set, so no point invalidating if the
# user is already there # user is already there

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@ -531,7 +531,7 @@ class RoomMemberWorkerStore(EventsWorkerStore):
# If we do then we can reuse that result and simply update it with # If we do then we can reuse that result and simply update it with
# any membership changes in `delta_ids` # any membership changes in `delta_ids`
if context.prev_group and context.delta_ids: if context.prev_group and context.delta_ids:
prev_res = self._get_joined_users_from_context.cache.get( prev_res = self._get_joined_users_from_context.cache.get_immediate(
(room_id, context.prev_group), None (room_id, context.prev_group), None
) )
if prev_res and isinstance(prev_res, dict): if prev_res and isinstance(prev_res, dict):

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@ -17,7 +17,16 @@
import enum import enum
import threading import threading
from typing import Callable, Generic, Iterable, MutableMapping, Optional, TypeVar, cast from typing import (
Callable,
Generic,
Iterable,
MutableMapping,
Optional,
TypeVar,
Union,
cast,
)
from prometheus_client import Gauge from prometheus_client import Gauge
@ -33,7 +42,7 @@ cache_pending_metric = Gauge(
["name"], ["name"],
) )
T = TypeVar("T")
KT = TypeVar("KT") KT = TypeVar("KT")
VT = TypeVar("VT") VT = TypeVar("VT")
@ -119,21 +128,21 @@ class DeferredCache(Generic[KT, VT]):
def get( def get(
self, self,
key: KT, key: KT,
default=_Sentinel.sentinel,
callback: Optional[Callable[[], None]] = None, callback: Optional[Callable[[], None]] = None,
update_metrics: bool = True, update_metrics: bool = True,
): ) -> Union[ObservableDeferred, VT]:
"""Looks the key up in the caches. """Looks the key up in the caches.
Args: Args:
key(tuple) key(tuple)
default: What is returned if key is not in the caches. If not
specified then function throws KeyError instead
callback(fn): Gets called when the entry in the cache is invalidated callback(fn): Gets called when the entry in the cache is invalidated
update_metrics (bool): whether to update the cache hit rate metrics update_metrics (bool): whether to update the cache hit rate metrics
Returns: Returns:
Either an ObservableDeferred or the result itself Either an ObservableDeferred or the result itself
Raises:
KeyError if the key is not found in the cache
""" """
callbacks = [callback] if callback else [] callbacks = [callback] if callback else []
val = self._pending_deferred_cache.get(key, _Sentinel.sentinel) val = self._pending_deferred_cache.get(key, _Sentinel.sentinel)
@ -145,13 +154,19 @@ class DeferredCache(Generic[KT, VT]):
m.inc_hits() m.inc_hits()
return val.deferred return val.deferred
val = self.cache.get( val2 = self.cache.get(
key, default, callbacks=callbacks, update_metrics=update_metrics key, _Sentinel.sentinel, callbacks=callbacks, update_metrics=update_metrics
) )
if val is _Sentinel.sentinel: if val2 is _Sentinel.sentinel:
raise KeyError() raise KeyError()
else: else:
return val return val2
def get_immediate(
self, key: KT, default: T, update_metrics: bool = True
) -> Union[VT, T]:
"""If we have a *completed* cached value, return it."""
return self.cache.get(key, default, update_metrics=update_metrics)
def set( def set(
self, self,

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@ -38,6 +38,22 @@ class DeferredCacheTestCase(unittest.TestCase):
self.assertEquals(cache.get("foo"), 123) self.assertEquals(cache.get("foo"), 123)
def test_get_immediate(self):
cache = DeferredCache("test")
d1 = defer.Deferred()
cache.set("key1", d1)
# get_immediate should return default
v = cache.get_immediate("key1", 1)
self.assertEqual(v, 1)
# now complete the set
d1.callback(2)
# get_immediate should return result
v = cache.get_immediate("key1", 1)
self.assertEqual(v, 2)
def test_invalidate(self): def test_invalidate(self):
cache = DeferredCache("test") cache = DeferredCache("test")
cache.prefill(("foo",), 123) cache.prefill(("foo",), 123)
@ -80,9 +96,11 @@ class DeferredCacheTestCase(unittest.TestCase):
# now do the invalidation # now do the invalidation
cache.invalidate_all() cache.invalidate_all()
# lookup should return none # lookup should fail
self.assertIsNone(cache.get("key1", None)) with self.assertRaises(KeyError):
self.assertIsNone(cache.get("key2", None)) cache.get("key1")
with self.assertRaises(KeyError):
cache.get("key2")
# both callbacks should have been callbacked # both callbacks should have been callbacked
self.assertTrue(callback_record[0], "Invalidation callback for key1 not called") self.assertTrue(callback_record[0], "Invalidation callback for key1 not called")
@ -90,7 +108,8 @@ class DeferredCacheTestCase(unittest.TestCase):
# letting the other lookup complete should do nothing # letting the other lookup complete should do nothing
d1.callback("result1") d1.callback("result1")
self.assertIsNone(cache.get("key1", None)) with self.assertRaises(KeyError):
cache.get("key1", None)
def test_eviction(self): def test_eviction(self):
cache = DeferredCache( cache = DeferredCache(