1 files changed, 5 insertions, 0 deletions
diff --git a/synapse/util/async.py b/synapse/util/async.py
index 0fd5b42523..a0a9039475 100644
--- a/synapse/util/async.py
+++ b/synapse/util/async.py
@@ -53,6 +53,11 @@ class ObservableDeferred(object):
 
     Cancelling or otherwise resolving an observer will not affect the original
     ObservableDeferred.
+
+    NB that it does not attempt to do anything with logcontexts; in general
+    you should probably make_deferred_yieldable the deferreds
+    returned by `observe`, and ensure that the original deferred runs its
+    callbacks in the sentinel logcontext.
     """
 
     __slots__ = ["_deferred", "_observers", "_result"]