Matrix-Mirrors/anonymousland-synapse
1
0
Fork 0
mirror of https://git.anonymousland.org/anonymousland/synapse.git synced 2025-05-08 03:34:55 -04:00
Code Issues Projects Releases Packages Wiki Activity

Implement and use an @lru_cache decorator (#8595)

Browse source 
We don't always need the full power of a DeferredCache.
This commit is contained in:
Richard van der Hoff 2020-10-30 11:43:17 +00:00 • committed by GitHub
parent fd7c743445
commit cbc82aa09f
No known key found for this signature in database
GPG key ID: 4AEE18F83AFDEB23
4 changed files with 272 additions and 61 deletions
Download patch file Download diff file Expand all files Collapse all files

235
synapse/util/caches/descriptors.py
View file

@ -13,10 +13,23 @@
# 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
from typing import Any, Callable, Generic, Optional, Tuple, TypeVar, Union, cast
from typing import (
Any,
Callable,
Generic,
Iterable,
Mapping,
Optional,
Sequence,
Tuple,
TypeVar,
Union,
cast,
)
from weakref import WeakValueDictionary
from twisted.internet import defer
@ -24,6 +37,7 @@ from twisted.internet import defer
from synapse.logging.context import make_deferred_yieldable, preserve_fn
from synapse.util import unwrapFirstError
from synapse.util.caches.deferred_cache import DeferredCache
from synapse.util.caches.lrucache import LruCache
logger = logging.getLogger(__name__)
@ -48,7 +62,7 @@ class _CachedFunction(Generic[F]):
class _CacheDescriptorBase:
def __init__(self, orig: _CachedFunction, num_args, cache_context=False):
def __init__(self, orig: Callable[..., Any], num_args, cache_context=False):
self.orig = orig
arg_spec = inspect.getfullargspec(orig)
@ -97,8 +111,107 @@ class _CacheDescriptorBase:
self.add_cache_context = cache_context
self.cache_key_builder = get_cache_key_builder(
self.arg_names, self.arg_defaults
)
class CacheDescriptor(_CacheDescriptorBase):
class _LruCachedFunction(Generic[F]):
cache = None # type: LruCache[CacheKey, Any]
__call__ = None # type: F
def lru_cache(
max_entries: int = 1000, cache_context: bool = False,
) -> Callable[[F], _LruCachedFunction[F]]:
"""A method decorator that applies a memoizing cache around the function.
This is more-or-less a drop-in equivalent to functools.lru_cache, although note
that the signature is slightly different.
The main differences with functools.lru_cache are:
(a) the size of the cache can be controlled via the cache_factor mechanism
(b) the wrapped function can request a "cache_context" which provides a
callback mechanism to indicate that the result is no longer valid
(c) prometheus metrics are exposed automatically.
The function should take zero or more arguments, which are used as the key for the
cache. Single-argument functions use that argument as the cache key; otherwise the
arguments are built into a tuple.
Cached functions can be "chained" (i.e. a cached function can call other cached
functions and get appropriately invalidated when they called caches are
invalidated) by adding a special "cache_context" argument to the function
and passing that as a kwarg to all caches called. For example:
@lru_cache(cache_context=True)
def foo(self, key, cache_context):
r1 = self.bar1(key, on_invalidate=cache_context.invalidate)
r2 = self.bar2(key, on_invalidate=cache_context.invalidate)
return r1 + r2
The wrapped function also has a 'cache' property which offers direct access to the
underlying LruCache.
"""
def func(orig: F) -> _LruCachedFunction[F]:
desc = LruCacheDescriptor(
orig, max_entries=max_entries, cache_context=cache_context,
)
return cast(_LruCachedFunction[F], desc)
return func
class LruCacheDescriptor(_CacheDescriptorBase):
"""Helper for @lru_cache"""
class _Sentinel(enum.Enum):
sentinel = object()
def __init__(
self, orig, max_entries: int = 1000, cache_context: bool = False,
):
super().__init__(orig, num_args=None, cache_context=cache_context)
self.max_entries = max_entries
def __get__(self, obj, owner):
cache = LruCache(
cache_name=self.orig.__name__, max_size=self.max_entries,
) # type: LruCache[CacheKey, Any]
get_cache_key = self.cache_key_builder
sentinel = LruCacheDescriptor._Sentinel.sentinel
@functools.wraps(self.orig)
def _wrapped(*args, **kwargs):
invalidate_callback = kwargs.pop("on_invalidate", None)
callbacks = (invalidate_callback,) if invalidate_callback else ()
cache_key = get_cache_key(args, kwargs)
ret = cache.get(cache_key, default=sentinel, callbacks=callbacks)
if ret != sentinel:
return ret
# Add our own `cache_context` to argument list if the wrapped function
# has asked for one
if self.add_cache_context:
kwargs["cache_context"] = _CacheContext.get_instance(cache, cache_key)
ret2 = self.orig(obj, *args, **kwargs)
cache.set(cache_key, ret2, callbacks=callbacks)
return ret2
wrapped = cast(_CachedFunction, _wrapped)
wrapped.cache = cache
obj.__dict__[self.orig.__name__] = wrapped
return wrapped
class DeferredCacheDescriptor(_CacheDescriptorBase):
""" A method decorator that applies a memoizing cache around the function.
This caches deferreds, rather than the results themselves. Deferreds that
@ -141,7 +254,6 @@ class CacheDescriptor(_CacheDescriptorBase):
cache_context=False,
iterable=False,
):
super().__init__(orig, num_args=num_args, cache_context=cache_context)
self.max_entries = max_entries
@ -157,41 +269,7 @@ class CacheDescriptor(_CacheDescriptorBase):
iterable=self.iterable,
) # type: DeferredCache[CacheKey, Any]
def get_cache_key_gen(args, kwargs):
"""Given some args/kwargs return a generator that resolves into
the cache_key.
We loop through each arg name, looking up if its in the `kwargs`,
otherwise using the next argument in `args`. If there are no more
args then we try looking the arg name up in the defaults
"""
pos = 0
for nm in self.arg_names:
if nm in kwargs:
yield kwargs[nm]
elif pos < len(args):
yield args[pos]
pos += 1
else:
yield self.arg_defaults[nm]
# By default our cache key is a tuple, but if there is only one item
# then don't bother wrapping in a tuple. This is to save memory.
if self.num_args == 1:
nm = self.arg_names[0]
def get_cache_key(args, kwargs):
if nm in kwargs:
return kwargs[nm]
elif len(args):
return args[0]
else:
return self.arg_defaults[nm]
else:
def get_cache_key(args, kwargs):
return tuple(get_cache_key_gen(args, kwargs))
get_cache_key = self.cache_key_builder
@functools.wraps(self.orig)
def _wrapped(*args, **kwargs):
@ -223,7 +301,6 @@ class CacheDescriptor(_CacheDescriptorBase):
wrapped.prefill = lambda key, val: cache.prefill(key[0], val)
else:
wrapped.invalidate = cache.invalidate
wrapped.invalidate_all = cache.invalidate_all
wrapped.invalidate_many = cache.invalidate_many
wrapped.prefill = cache.prefill
@ -236,7 +313,7 @@ class CacheDescriptor(_CacheDescriptorBase):
return wrapped
class CacheListDescriptor(_CacheDescriptorBase):
class DeferredCacheListDescriptor(_CacheDescriptorBase):
"""Wraps an existing cache to support bulk fetching of keys.
Given a list of keys it looks in the cache to find any hits, then passes
@ -382,11 +459,13 @@ class _CacheContext:
on a lower level.
"""
Cache = Union[DeferredCache, LruCache]
_cache_context_objects = (
WeakValueDictionary()
) # type: WeakValueDictionary[Tuple[DeferredCache, CacheKey], _CacheContext]
) # type: WeakValueDictionary[Tuple[_CacheContext.Cache, CacheKey], _CacheContext]
def __init__(self, cache, cache_key): # type: (DeferredCache, CacheKey) -> None
def __init__(self, cache: "_CacheContext.Cache", cache_key: CacheKey) -> None:
self._cache = cache
self._cache_key = cache_key
@ -396,8 +475,8 @@ class _CacheContext:
@classmethod
def get_instance(
cls, cache, cache_key
): # type: (DeferredCache, CacheKey) -> _CacheContext
cls, cache: "_CacheContext.Cache", cache_key: CacheKey
) -> "_CacheContext":
"""Returns an instance constructed with the given arguments.
A new instance is only created if none already exists.
@ -418,7 +497,7 @@ def cached(
cache_context: bool = False,
iterable: bool = False,
) -> Callable[[F], _CachedFunction[F]]:
func = lambda orig: CacheDescriptor(
func = lambda orig: DeferredCacheDescriptor(
orig,
max_entries=max_entries,
num_args=num_args,
@ -460,7 +539,7 @@ def cachedList(
def batch_do_something(self, first_arg, second_args):
...
"""
func = lambda orig: CacheListDescriptor(
func = lambda orig: DeferredCacheListDescriptor(
orig,
cached_method_name=cached_method_name,
list_name=list_name,
@ -468,3 +547,65 @@ def cachedList(
)
return cast(Callable[[F], _CachedFunction[F]], func)
def get_cache_key_builder(
param_names: Sequence[str], param_defaults: Mapping[str, Any]
) -> Callable[[Sequence[Any], Mapping[str, Any]], CacheKey]:
"""Construct a function which will build cache keys suitable for a cached function
Args:
param_names: list of formal parameter names for the cached function
param_defaults: a mapping from parameter name to default value for that param
Returns:
A function which will take an (args, kwargs) pair and return a cache key
"""
# By default our cache key is a tuple, but if there is only one item
# then don't bother wrapping in a tuple. This is to save memory.
if len(param_names) == 1:
nm = param_names[0]
def get_cache_key(args: Sequence[Any], kwargs: Mapping[str, Any]) -> CacheKey:
if nm in kwargs:
return kwargs[nm]
elif len(args):
return args[0]
else:
return param_defaults[nm]
else:
def get_cache_key(args: Sequence[Any], kwargs: Mapping[str, Any]) -> CacheKey:
return tuple(_get_cache_key_gen(param_names, param_defaults, args, kwargs))
return get_cache_key
def _get_cache_key_gen(
param_names: Iterable[str],
param_defaults: Mapping[str, Any],
args: Sequence[Any],
kwargs: Mapping[str, Any],
) -> Iterable[Any]:
"""Given some args/kwargs return a generator that resolves into
the cache_key.
This is essentially the same operation as `inspect.getcallargs`, but optimised so
that we don't need to inspect the target function for each call.
"""
# We loop through each arg name, looking up if its in the `kwargs`,
# otherwise using the next argument in `args`. If there are no more
# args then we try looking the arg name up in the defaults.
pos = 0
for nm in param_names:
if nm in kwargs:
yield kwargs[nm]
elif pos < len(args):
yield args[pos]
pos += 1
else:
yield param_defaults[nm]