1 files changed, 10 insertions, 6 deletions
diff --git a/synapse/metrics/_exposition.py b/synapse/metrics/_exposition.py
index 74d9c3ecd3..ab7f948ed4 100644
--- a/synapse/metrics/_exposition.py
+++ b/synapse/metrics/_exposition.py
@@ -33,12 +33,14 @@ from prometheus_client import REGISTRY
 
 from twisted.web.resource import Resource
 
+from synapse.util import caches
+
 try:
     from prometheus_client.samples import Sample
 except ImportError:
-    Sample = namedtuple(
+    Sample = namedtuple(  # type: ignore[no-redef] # noqa
         "Sample", ["name", "labels", "value", "timestamp", "exemplar"]
-    )  # type: ignore
+    )
 
 
 CONTENT_TYPE_LATEST = str("text/plain; version=0.0.4; charset=utf-8")
@@ -103,13 +105,15 @@ def nameify_sample(sample):
 
 
 def generate_latest(registry, emit_help=False):
-    output = []
 
-    for metric in registry.collect():
+    # Trigger the cache metrics to be rescraped, which updates the common
+    # metrics but do not produce metrics themselves
+    for collector in caches.collectors_by_name.values():
+        collector.collect()
 
-        if metric.name.startswith("__unused"):
-            continue
+    output = []
 
+    for metric in registry.collect():
         if not metric.samples:
             # No samples, don't bother.
             continue