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-rw-r--r--synapse/util/caches/descriptors.py30
1 files changed, 14 insertions, 16 deletions
diff --git a/synapse/util/caches/descriptors.py b/synapse/util/caches/descriptors.py
index 19595df422..5c30ed235d 100644
--- a/synapse/util/caches/descriptors.py
+++ b/synapse/util/caches/descriptors.py
@@ -15,12 +15,9 @@
 import logging
 
 from synapse.util.async import ObservableDeferred
-from synapse.util import unwrapFirstError
+from synapse.util import unwrapFirstError, logcontext
 from synapse.util.caches.lrucache import LruCache
 from synapse.util.caches.treecache import TreeCache, iterate_tree_cache_entry
-from synapse.util.logcontext import (
-    PreserveLoggingContext, preserve_context_over_deferred, preserve_context_over_fn
-)
 
 from . import DEBUG_CACHES, register_cache
 
@@ -328,11 +325,9 @@ class CacheDescriptor(_CacheDescriptorBase):
                         defer.returnValue(cached_result)
                     observer.addCallback(check_result)
 
-                return preserve_context_over_deferred(observer)
             except KeyError:
                 ret = defer.maybeDeferred(
-                    preserve_context_over_fn,
-                    self.function_to_call,
+                    logcontext.preserve_fn(self.function_to_call),
                     obj, *args, **kwargs
                 )
 
@@ -342,10 +337,11 @@ class CacheDescriptor(_CacheDescriptorBase):
 
                 ret.addErrback(onErr)
 
-                ret = ObservableDeferred(ret, consumeErrors=True)
-                cache.set(cache_key, ret, callback=invalidate_callback)
+                result_d = ObservableDeferred(ret, consumeErrors=True)
+                cache.set(cache_key, result_d, callback=invalidate_callback)
+                observer = result_d.observe()
 
-                return preserve_context_over_deferred(ret.observe())
+            return logcontext.make_deferred_yieldable(observer)
 
         wrapped.invalidate = cache.invalidate
         wrapped.invalidate_all = cache.invalidate_all
@@ -362,7 +358,11 @@ class CacheListDescriptor(_CacheDescriptorBase):
     """Wraps an existing cache to support bulk fetching of keys.
 
     Given a list of keys it looks in the cache to find any hits, then passes
-    the list of missing keys to the wrapped fucntion.
+    the list of missing keys to the wrapped function.
+
+    Once wrapped, the function returns either a Deferred which resolves to
+    the list of results, or (if all results were cached), just the list of
+    results.
     """
 
     def __init__(self, orig, cached_method_name, list_name, num_args=None,
@@ -433,8 +433,7 @@ class CacheListDescriptor(_CacheDescriptorBase):
                 args_to_call[self.list_name] = missing
 
                 ret_d = defer.maybeDeferred(
-                    preserve_context_over_fn,
-                    self.function_to_call,
+                    logcontext.preserve_fn(self.function_to_call),
                     **args_to_call
                 )
 
@@ -443,8 +442,7 @@ class CacheListDescriptor(_CacheDescriptorBase):
                 # We need to create deferreds for each arg in the list so that
                 # we can insert the new deferred into the cache.
                 for arg in missing:
-                    with PreserveLoggingContext():
-                        observer = ret_d.observe()
+                    observer = ret_d.observe()
                     observer.addCallback(lambda r, arg: r.get(arg, None), arg)
 
                     observer = ObservableDeferred(observer)
@@ -471,7 +469,7 @@ class CacheListDescriptor(_CacheDescriptorBase):
                     results.update(res)
                     return results
 
-                return preserve_context_over_deferred(defer.gatherResults(
+                return logcontext.make_deferred_yieldable(defer.gatherResults(
                     cached_defers.values(),
                     consumeErrors=True,
                 ).addCallback(update_results_dict).addErrback(