Ensure that we do not cache empty sync responses after a timeout (#10158)

Fixes #8518 by telling the ResponseCache not to cache the /sync response if the next_batch param is the same as the since token.

1 files changed, 2 insertions, 4 deletions

diff --git a/synapse/python_dependencies.py b/synapse/python_dependencies.py

index 546231bec0..bf361c42d6 100644
--- a/synapse/python_dependencies.py
+++ b/synapse/python_dependencies.py
@@ -75,11 +75,9 @@ REQUIREMENTS = [
     "phonenumbers>=8.2.0",
     # we use GaugeHistogramMetric, which was added in prom-client 0.4.0.
     "prometheus_client>=0.4.0",
-    # we use attr.validators.deep_iterable, which arrived in 19.1.0 (Note:
-    # Fedora 31 only has 19.1, so if we want to upgrade we should wait until 33
-    # is out in November.)
+    # we use `order`, which arrived in attrs 19.2.0.
     # Note: 21.1.0 broke `/sync`, see #9936
-    "attrs>=19.1.0,!=21.1.0",
+    "attrs>=19.2.0,!=21.1.0",
     "netaddr>=0.7.18",
     "Jinja2>=2.9",
     "bleach>=1.4.3",