From 1f4269700c2353263a605856f28ded28501368e1 Mon Sep 17 00:00:00 2001
From: Richard van der Hoff <richard@matrix.org>
Date: Fri, 16 Oct 2020 12:34:55 +0100
Subject: Push some deferred wrangling down into DeferredCache

---
 synapse/util/caches/descriptors.py | 32 +++++++-------------------------
 1 file changed, 7 insertions(+), 25 deletions(-)

(limited to 'synapse/util/caches/descriptors.py')

diff --git a/synapse/util/caches/descriptors.py b/synapse/util/caches/descriptors.py
index 1f43886804..a4172345ef 100644
--- a/synapse/util/caches/descriptors.py
+++ b/synapse/util/caches/descriptors.py
@@ -23,7 +23,6 @@ from twisted.internet import defer
 
 from synapse.logging.context import make_deferred_yieldable, preserve_fn
 from synapse.util import unwrapFirstError
-from synapse.util.async_helpers import ObservableDeferred
 from synapse.util.caches.deferred_cache import DeferredCache
 
 logger = logging.getLogger(__name__)
@@ -156,7 +155,7 @@ class CacheDescriptor(_CacheDescriptorBase):
             keylen=self.num_args,
             tree=self.tree,
             iterable=self.iterable,
-        )  # type: DeferredCache[Tuple, Any]
+        )  # type: DeferredCache[CacheKey, Any]
 
         def get_cache_key_gen(args, kwargs):
             """Given some args/kwargs return a generator that resolves into
@@ -208,26 +207,12 @@ class CacheDescriptor(_CacheDescriptorBase):
                 kwargs["cache_context"] = _CacheContext.get_instance(cache, cache_key)
 
             try:
-                cached_result_d = cache.get(cache_key, callback=invalidate_callback)
-
-                if isinstance(cached_result_d, ObservableDeferred):
-                    observer = cached_result_d.observe()
-                else:
-                    observer = defer.succeed(cached_result_d)
-
+                ret = cache.get(cache_key, callback=invalidate_callback)
             except KeyError:
                 ret = defer.maybeDeferred(preserve_fn(self.orig), obj, *args, **kwargs)
+                ret = cache.set(cache_key, ret, callback=invalidate_callback)
 
-                def onErr(f):
-                    cache.invalidate(cache_key)
-                    return f
-
-                ret.addErrback(onErr)
-
-                result_d = cache.set(cache_key, ret, callback=invalidate_callback)
-                observer = result_d.observe()
-
-            return make_deferred_yieldable(observer)
+            return make_deferred_yieldable(ret)
 
         wrapped = cast(_CachedFunction, _wrapped)
 
@@ -286,7 +271,7 @@ class CacheListDescriptor(_CacheDescriptorBase):
 
     def __get__(self, obj, objtype=None):
         cached_method = getattr(obj, self.cached_method_name)
-        cache = cached_method.cache
+        cache = cached_method.cache  # type: DeferredCache[CacheKey, Any]
         num_args = cached_method.num_args
 
         @functools.wraps(self.orig)
@@ -326,14 +311,11 @@ class CacheListDescriptor(_CacheDescriptorBase):
             for arg in list_args:
                 try:
                     res = cache.get(arg_to_cache_key(arg), callback=invalidate_callback)
-                    if not isinstance(res, ObservableDeferred):
-                        results[arg] = res
-                    elif not res.has_succeeded():
-                        res = res.observe()
+                    if not res.called:
                         res.addCallback(update_results_dict, arg)
                         cached_defers.append(res)
                     else:
-                        results[arg] = res.get_result()
+                        results[arg] = res.result
                 except KeyError:
                     missing.add(arg)
 
-- 
cgit 1.5.1


From b28aaeb3a567ce1bbfd41796362b8bb0813ed0e3 Mon Sep 17 00:00:00 2001
From: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>
Date: Wed, 21 Oct 2020 22:57:45 +0100
Subject: Optimise CacheDescriptor (#8594)

don't bother constricting a CacheContext unless we need one.
---
 changelog.d/8594.misc              |  1 +
 synapse/util/caches/descriptors.py | 12 +++++++-----
 2 files changed, 8 insertions(+), 5 deletions(-)
 create mode 100644 changelog.d/8594.misc

(limited to 'synapse/util/caches/descriptors.py')

diff --git a/changelog.d/8594.misc b/changelog.d/8594.misc
new file mode 100644
index 0000000000..d266ba19a4
--- /dev/null
+++ b/changelog.d/8594.misc
@@ -0,0 +1 @@
+Minor optimisations in caching code.
diff --git a/synapse/util/caches/descriptors.py b/synapse/util/caches/descriptors.py
index a4172345ef..5d7fffee66 100644
--- a/synapse/util/caches/descriptors.py
+++ b/synapse/util/caches/descriptors.py
@@ -201,14 +201,16 @@ class CacheDescriptor(_CacheDescriptorBase):
 
             cache_key = get_cache_key(args, kwargs)
 
-            # 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)
-
             try:
                 ret = cache.get(cache_key, callback=invalidate_callback)
             except KeyError:
+                # 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
+                    )
+
                 ret = defer.maybeDeferred(preserve_fn(self.orig), obj, *args, **kwargs)
                 ret = cache.set(cache_key, ret, callback=invalidate_callback)
 
-- 
cgit 1.5.1