diff options
| -rw-r--r-- | synapse/storage/_base.py | 30 |
1 files changed, 27 insertions, 3 deletions
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() |