diff --git a/synapse/util/caches/descriptors.py b/synapse/util/caches/descriptors.py
index 7c9fe199bf..1f43886804 100644
--- a/synapse/util/caches/descriptors.py
+++ b/synapse/util/caches/descriptors.py
@@ -13,44 +13,24 @@
# 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.
-import enum
import functools
import inspect
import logging
-import threading
-from typing import (
- Any,
- Callable,
- Generic,
- Iterable,
- MutableMapping,
- Optional,
- Tuple,
- TypeVar,
- Union,
- cast,
-)
+from typing import Any, Callable, Generic, Optional, Tuple, TypeVar, Union, cast
from weakref import WeakValueDictionary
-from prometheus_client import Gauge
-
from twisted.internet import defer
from synapse.logging.context import make_deferred_yieldable, preserve_fn
from synapse.util import unwrapFirstError
from synapse.util.async_helpers import ObservableDeferred
-from synapse.util.caches.lrucache import LruCache
-from synapse.util.caches.treecache import TreeCache, iterate_tree_cache_entry
-
-from . import register_cache
+from synapse.util.caches.deferred_cache import DeferredCache
logger = logging.getLogger(__name__)
CacheKey = Union[Tuple, Any]
F = TypeVar("F", bound=Callable[..., Any])
-KT = TypeVar("KT")
-VT = TypeVar("VT")
class _CachedFunction(Generic[F]):
@@ -68,266 +48,6 @@ class _CachedFunction(Generic[F]):
__call__ = None # type: F
-cache_pending_metric = Gauge(
- "synapse_util_caches_cache_pending",
- "Number of lookups currently pending for this cache",
- ["name"],
-)
-
-
-class _Sentinel(enum.Enum):
- # defining a sentinel in this way allows mypy to correctly handle the
- # type of a dictionary lookup.
- sentinel = object()
-
-
-class CacheEntry:
- __slots__ = ["deferred", "callbacks", "invalidated"]
-
- def __init__(
- self, deferred: ObservableDeferred, callbacks: Iterable[Callable[[], None]]
- ):
- self.deferred = deferred
- self.callbacks = set(callbacks)
- self.invalidated = False
-
- def invalidate(self):
- if not self.invalidated:
- self.invalidated = True
- for callback in self.callbacks:
- callback()
- self.callbacks.clear()
-
-
-class DeferredCache(Generic[KT, VT]):
- """Wraps an LruCache, adding support for Deferred results.
-
- It expects that each entry added with set() will be a Deferred; likewise get()
- may return an ObservableDeferred.
- """
-
- __slots__ = (
- "cache",
- "name",
- "keylen",
- "thread",
- "metrics",
- "_pending_deferred_cache",
- )
-
- def __init__(
- self,
- name: str,
- max_entries: int = 1000,
- keylen: int = 1,
- tree: bool = False,
- iterable: bool = False,
- apply_cache_factor_from_config: bool = True,
- ):
- """
- Args:
- name: The name of the cache
- max_entries: Maximum amount of entries that the cache will hold
- keylen: The length of the tuple used as the cache key. Ignored unless
- `tree` is True.
- tree: Use a TreeCache instead of a dict as the underlying cache type
- iterable: If True, count each item in the cached object as an entry,
- rather than each cached object
- apply_cache_factor_from_config: Whether cache factors specified in the
- config file affect `max_entries`
- """
- cache_type = TreeCache if tree else dict
-
- # _pending_deferred_cache maps from the key value to a `CacheEntry` object.
- self._pending_deferred_cache = (
- cache_type()
- ) # type: MutableMapping[KT, CacheEntry]
-
- # cache is used for completed results and maps to the result itself, rather than
- # a Deferred.
- self.cache = LruCache(
- max_size=max_entries,
- keylen=keylen,
- cache_type=cache_type,
- size_callback=(lambda d: len(d)) if iterable else None,
- evicted_callback=self._on_evicted,
- apply_cache_factor_from_config=apply_cache_factor_from_config,
- )
-
- self.name = name
- self.keylen = keylen
- self.thread = None # type: Optional[threading.Thread]
- self.metrics = register_cache(
- "cache",
- name,
- self.cache,
- collect_callback=self._metrics_collection_callback,
- )
-
- @property
- def max_entries(self):
- return self.cache.max_size
-
- def _on_evicted(self, evicted_count):
- self.metrics.inc_evictions(evicted_count)
-
- def _metrics_collection_callback(self):
- cache_pending_metric.labels(self.name).set(len(self._pending_deferred_cache))
-
- def check_thread(self):
- expected_thread = self.thread
- if expected_thread is None:
- self.thread = threading.current_thread()
- else:
- if expected_thread is not threading.current_thread():
- raise ValueError(
- "Cache objects can only be accessed from the main thread"
- )
-
- def get(
- self,
- key: KT,
- default=_Sentinel.sentinel,
- callback: Optional[Callable[[], None]] = None,
- update_metrics: bool = True,
- ):
- """Looks the key up in the caches.
-
- Args:
- 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
- update_metrics (bool): whether to update the cache hit rate metrics
-
- Returns:
- Either an ObservableDeferred or the result itself
- """
- callbacks = [callback] if callback else []
- val = self._pending_deferred_cache.get(key, _Sentinel.sentinel)
- if val is not _Sentinel.sentinel:
- val.callbacks.update(callbacks)
- if update_metrics:
- self.metrics.inc_hits()
- return val.deferred
-
- val = self.cache.get(key, _Sentinel.sentinel, callbacks=callbacks)
- if val is not _Sentinel.sentinel:
- self.metrics.inc_hits()
- return val
-
- if update_metrics:
- self.metrics.inc_misses()
-
- if default is _Sentinel.sentinel:
- raise KeyError()
- else:
- return default
-
- def set(
- self,
- key: KT,
- value: defer.Deferred,
- callback: Optional[Callable[[], None]] = None,
- ) -> ObservableDeferred:
- if not isinstance(value, defer.Deferred):
- raise TypeError("not a Deferred")
-
- callbacks = [callback] if callback else []
- self.check_thread()
- observable = ObservableDeferred(value, consumeErrors=True)
- observer = observable.observe()
- entry = CacheEntry(deferred=observable, callbacks=callbacks)
-
- existing_entry = self._pending_deferred_cache.pop(key, None)
- if existing_entry:
- existing_entry.invalidate()
-
- self._pending_deferred_cache[key] = entry
-
- def compare_and_pop():
- """Check if our entry is still the one in _pending_deferred_cache, and
- if so, pop it.
-
- Returns true if the entries matched.
- """
- existing_entry = self._pending_deferred_cache.pop(key, None)
- if existing_entry is entry:
- return True
-
- # oops, the _pending_deferred_cache has been updated since
- # we started our query, so we are out of date.
- #
- # Better put back whatever we took out. (We do it this way
- # round, rather than peeking into the _pending_deferred_cache
- # and then removing on a match, to make the common case faster)
- if existing_entry is not None:
- self._pending_deferred_cache[key] = existing_entry
-
- return False
-
- def cb(result):
- if compare_and_pop():
- self.cache.set(key, result, entry.callbacks)
- else:
- # we're not going to put this entry into the cache, so need
- # to make sure that the invalidation callbacks are called.
- # That was probably done when _pending_deferred_cache was
- # updated, but it's possible that `set` was called without
- # `invalidate` being previously called, in which case it may
- # not have been. Either way, let's double-check now.
- entry.invalidate()
-
- def eb(_fail):
- compare_and_pop()
- entry.invalidate()
-
- # once the deferred completes, we can move the entry from the
- # _pending_deferred_cache to the real cache.
- #
- observer.addCallbacks(cb, eb)
- return observable
-
- def prefill(self, key: KT, value: VT, callback: Callable[[], None] = None):
- callbacks = [callback] if callback else []
- self.cache.set(key, value, callbacks=callbacks)
-
- def invalidate(self, key):
- self.check_thread()
- self.cache.pop(key, None)
-
- # if we have a pending lookup for this key, remove it from the
- # _pending_deferred_cache, which will (a) stop it being returned
- # for future queries and (b) stop it being persisted as a proper entry
- # in self.cache.
- entry = self._pending_deferred_cache.pop(key, None)
-
- # run the invalidation callbacks now, rather than waiting for the
- # deferred to resolve.
- if entry:
- entry.invalidate()
-
- def invalidate_many(self, key: KT):
- self.check_thread()
- if not isinstance(key, tuple):
- raise TypeError("The cache key must be a tuple not %r" % (type(key),))
- self.cache.del_multi(key)
-
- # if we have a pending lookup for this key, remove it from the
- # _pending_deferred_cache, as above
- entry_dict = self._pending_deferred_cache.pop(cast(KT, key), None)
- if entry_dict is not None:
- for entry in iterate_tree_cache_entry(entry_dict):
- entry.invalidate()
-
- def invalidate_all(self):
- self.check_thread()
- self.cache.clear()
- for entry in self._pending_deferred_cache.values():
- entry.invalidate()
- self._pending_deferred_cache.clear()
-
-
class _CacheDescriptorBase:
def __init__(self, orig: _CachedFunction, num_args, cache_context=False):
self.orig = orig
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