Track cache invalidations (#12000)

Currently we only track evictions due to size or time constraints.

1 files changed, 5 insertions, 0 deletions

diff --git a/synapse/util/caches/expiringcache.py b/synapse/util/caches/expiringcache.py

index 67ee4c693b..c6a5d0dfc0 100644
--- a/synapse/util/caches/expiringcache.py
+++ b/synapse/util/caches/expiringcache.py
@@ -133,6 +133,11 @@ class ExpiringCache(Generic[KT, VT]):
                 raise KeyError(key)
             return default
 
+        if self.iterable:
+            self.metrics.inc_evictions(EvictionReason.invalidation, len(value.value))
+        else:
+            self.metrics.inc_evictions(EvictionReason.invalidation)
+
         return value.value
 
     def __contains__(self, key: KT) -> bool: