diff --git a/synapse/storage/_base.py b/synapse/storage/_base.py
index 842c4e2982..d4751769e4 100644
--- a/synapse/storage/_base.py
+++ b/synapse/storage/_base.py
@@ -149,6 +149,9 @@ class Cache(object):
class CacheDescriptor(object):
""" A method decorator that applies a memoizing cache around the function.
+ This caches deferreds, rather than the results themselves. Deferreds that
+ fail are removed from the cache.
+
The function is presumed to take zero or more arguments, which are used in
a tuple as the key for the cache. Hits are served directly from the cache;
misses use the function body to generate the value.
@@ -195,8 +198,23 @@ class CacheDescriptor(object):
arg_dict = inspect.getcallargs(self.orig, obj, *args, **kwargs)
keyargs = [arg_dict[arg_nm] for arg_nm in self.arg_names]
try:
- cached_result = cache.get(*keyargs)
- return cached_result.observe()
+ cached_result_d = cache.get(*keyargs)
+
+ if DEBUG_CACHES:
+
+ @defer.inlineCallbacks
+ def check_result(cached_result):
+ actual_result = yield self.function_to_call(obj, *args, **kwargs)
+ if actual_result != cached_result:
+ logger.error(
+ "Stale cache entry %s%r: cached: %r, actual %r",
+ self.orig.__name__, keyargs,
+ cached_result, actual_result,
+ )
+ raise ValueError("Stale cache entry")
+ cached_result_d.observe().addCallback(check_result)
+
+ return cached_result_d.observe()
except KeyError:
# Get the sequence number of the cache before reading from the
# database so that we can tell if the cache is invalidated
@@ -207,8 +225,14 @@ class CacheDescriptor(object):
self.function_to_call,
obj, *args, **kwargs
)
- ret = ObservableDeferred(ret, consumeErrors=False)
+ def onErr(f):
+ cache.invalidate(*keyargs)
+ return f
+
+ ret.addErrback(onErr)
+
+ ret = ObservableDeferred(ret, consumeErrors=False)
cache.update(sequence, *(keyargs + [ret]))
return ret.observe()
|
