diff --git a/synapse/util/caches/descriptors.py b/synapse/util/caches/descriptors.py
index 0e8da27f53..84f5ae22c3 100644
--- a/synapse/util/caches/descriptors.py
+++ b/synapse/util/caches/descriptors.py
@@ -17,8 +17,8 @@ import functools
import inspect
import logging
import threading
-from collections import namedtuple
-from typing import Any, cast
+from typing import Any, Tuple, Union, cast
+from weakref import WeakValueDictionary
from six import itervalues
@@ -38,6 +38,8 @@ from . import register_cache
logger = logging.getLogger(__name__)
+CacheKey = Union[Tuple, Any]
+
class _CachedFunction(Protocol):
invalidate = None # type: Any
@@ -430,7 +432,7 @@ class CacheDescriptor(_CacheDescriptorBase):
# 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(cache, cache_key)
+ kwargs["cache_context"] = _CacheContext.get_instance(cache, cache_key)
try:
cached_result_d = cache.get(cache_key, callback=invalidate_callback)
@@ -624,14 +626,38 @@ class CacheListDescriptor(_CacheDescriptorBase):
return wrapped
-class _CacheContext(namedtuple("_CacheContext", ("cache", "key"))):
- # We rely on _CacheContext implementing __eq__ and __hash__ sensibly,
- # which namedtuple does for us (i.e. two _CacheContext are the same if
- # their caches and keys match). This is important in particular to
- # dedupe when we add callbacks to lru cache nodes, otherwise the number
- # of callbacks would grow.
- def invalidate(self):
- self.cache.invalidate(self.key)
+class _CacheContext:
+ """Holds cache information from the cached function higher in the calling order.
+
+ Can be used to invalidate the higher level cache entry if something changes
+ on a lower level.
+ """
+
+ _cache_context_objects = (
+ WeakValueDictionary()
+ ) # type: WeakValueDictionary[Tuple[Cache, CacheKey], _CacheContext]
+
+ def __init__(self, cache, cache_key): # type: (Cache, CacheKey) -> None
+ self._cache = cache
+ self._cache_key = cache_key
+
+ def invalidate(self): # type: () -> None
+ """Invalidates the cache entry referred to by the context."""
+ self._cache.invalidate(self._cache_key)
+
+ @classmethod
+ def get_instance(cls, cache, cache_key): # type: (Cache, CacheKey) -> _CacheContext
+ """Returns an instance constructed with the given arguments.
+
+ A new instance is only created if none already exists.
+ """
+
+ # We make sure there are no identical _CacheContext instances. This is
+ # important in particular to dedupe when we add callbacks to lru cache
+ # nodes, otherwise the number of callbacks would grow.
+ return cls._cache_context_objects.setdefault(
+ (cache, cache_key), cls(cache, cache_key)
+ )
def cached(
diff --git a/synapse/util/httpresourcetree.py b/synapse/util/httpresourcetree.py
index 1a20c596bf..3c0e8469f3 100644
--- a/synapse/util/httpresourcetree.py
+++ b/synapse/util/httpresourcetree.py
@@ -20,7 +20,7 @@ logger = logging.getLogger(__name__)
def create_resource_tree(desired_tree, root_resource):
- """Create the resource tree for this Home Server.
+ """Create the resource tree for this homeserver.
This in unduly complicated because Twisted does not support putting
child resources more than 1 level deep at a time.
|
