diff options
Diffstat (limited to 'synapse/util/caches/descriptors.py')
| -rw-r--r-- | synapse/util/caches/descriptors.py | 284 |
1 files changed, 2 insertions, 282 deletions
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 |