diff options
| -rw-r--r-- | changelog.d/8593.misc | 1 | ||||
| -rw-r--r-- | synapse/util/caches/deferred_cache.py | 18 |
2 files changed, 16 insertions, 3 deletions
diff --git a/changelog.d/8593.misc b/changelog.d/8593.misc new file mode 100644 index 0000000000..d266ba19a4 --- /dev/null +++ b/changelog.d/8593.misc @@ -0,0 +1 @@ +Minor optimisations in caching code. diff --git a/synapse/util/caches/deferred_cache.py b/synapse/util/caches/deferred_cache.py index 6c162e9f34..601305487c 100644 --- a/synapse/util/caches/deferred_cache.py +++ b/synapse/util/caches/deferred_cache.py @@ -31,6 +31,7 @@ from typing import ( from prometheus_client import Gauge from twisted.internet import defer +from twisted.python import failure from synapse.util.async_helpers import ObservableDeferred from synapse.util.caches.lrucache import LruCache @@ -214,9 +215,6 @@ class DeferredCache(Generic[KT, VT]): 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: @@ -224,6 +222,20 @@ class DeferredCache(Generic[KT, VT]): # XXX: why don't we invalidate the entry in `self.cache` yet? + # we can save a whole load of effort if the deferred is ready. + if value.called: + result = value.result + if not isinstance(result, failure.Failure): + self.cache.set(key, result, callbacks) + return value + + # otherwise, we'll add an entry to the _pending_deferred_cache for now, + # and add callbacks to add it to the cache properly later. + + observable = ObservableDeferred(value, consumeErrors=True) + observer = observable.observe() + entry = CacheEntry(deferred=observable, callbacks=callbacks) + self._pending_deferred_cache[key] = entry def compare_and_pop(): |