Add support for evicting cache entries based on last access time. (#10205)

2 files changed, 43 insertions, 29 deletions

diff --git a/synapse/config/_base.pyi b/synapse/config/_base.pyi
index 23ca0c83c1..06fbd1166b 100644
--- a/synapse/config/_base.pyi
+++ b/synapse/config/_base.pyi
@@ -5,6 +5,7 @@ from synapse.config import (
     api,
     appservice,
     auth,
+    cache,
     captcha,
     cas,
     consent,
@@ -88,6 +89,7 @@ class RootConfig:
     tracer: tracer.TracerConfig
     redis: redis.RedisConfig
     modules: modules.ModulesConfig
+    caches: cache.CacheConfig
     federation: federation.FederationConfig
 
     config_classes: List = ...
diff --git a/synapse/config/cache.py b/synapse/config/cache.py
index 91165ee1ce..7789b40323 100644
--- a/synapse/config/cache.py
+++ b/synapse/config/cache.py
@@ -116,35 +116,41 @@ class CacheConfig(Config):
         #event_cache_size: 10K
 
         caches:
-           # Controls the global cache factor, which is the default cache factor
-           # for all caches if a specific factor for that cache is not otherwise
-           # set.
-           #
-           # This can also be set by the "SYNAPSE_CACHE_FACTOR" environment
-           # variable. Setting by environment variable takes priority over
-           # setting through the config file.
-           #
-           # Defaults to 0.5, which will half the size of all caches.
-           #
-           #global_factor: 1.0
-
-           # A dictionary of cache name to cache factor for that individual
-           # cache. Overrides the global cache factor for a given cache.
-           #
-           # These can also be set through environment variables comprised
-           # of "SYNAPSE_CACHE_FACTOR_" + the name of the cache in capital
-           # letters and underscores. Setting by environment variable
-           # takes priority over setting through the config file.
-           # Ex. SYNAPSE_CACHE_FACTOR_GET_USERS_WHO_SHARE_ROOM_WITH_USER=2.0
-           #
-           # Some caches have '*' and other characters that are not
-           # alphanumeric or underscores. These caches can be named with or
-           # without the special characters stripped. For example, to specify
-           # the cache factor for `*stateGroupCache*` via an environment
-           # variable would be `SYNAPSE_CACHE_FACTOR_STATEGROUPCACHE=2.0`.
-           #
-           per_cache_factors:
-             #get_users_who_share_room_with_user: 2.0
+          # Controls the global cache factor, which is the default cache factor
+          # for all caches if a specific factor for that cache is not otherwise
+          # set.
+          #
+          # This can also be set by the "SYNAPSE_CACHE_FACTOR" environment
+          # variable. Setting by environment variable takes priority over
+          # setting through the config file.
+          #
+          # Defaults to 0.5, which will half the size of all caches.
+          #
+          #global_factor: 1.0
+
+          # A dictionary of cache name to cache factor for that individual
+          # cache. Overrides the global cache factor for a given cache.
+          #
+          # These can also be set through environment variables comprised
+          # of "SYNAPSE_CACHE_FACTOR_" + the name of the cache in capital
+          # letters and underscores. Setting by environment variable
+          # takes priority over setting through the config file.
+          # Ex. SYNAPSE_CACHE_FACTOR_GET_USERS_WHO_SHARE_ROOM_WITH_USER=2.0
+          #
+          # Some caches have '*' and other characters that are not
+          # alphanumeric or underscores. These caches can be named with or
+          # without the special characters stripped. For example, to specify
+          # the cache factor for `*stateGroupCache*` via an environment
+          # variable would be `SYNAPSE_CACHE_FACTOR_STATEGROUPCACHE=2.0`.
+          #
+          per_cache_factors:
+            #get_users_who_share_room_with_user: 2.0
+
+          # Controls how long an entry can be in a cache without having been
+          # accessed before being evicted. Defaults to None, which means
+          # entries are never evicted based on time.
+          #
+          #expiry_time: 30m
         """
 
     def read_config(self, config, **kwargs):
@@ -200,6 +206,12 @@ class CacheConfig(Config):
                     e.message  # noqa: B306, DependencyException.message is a property
                 )
 
+        expiry_time = cache_config.get("expiry_time")
+        if expiry_time:
+            self.expiry_time_msec = self.parse_duration(expiry_time)
+        else:
+            self.expiry_time_msec = None
+
         # Resize all caches (if necessary) with the new factors we've loaded
         self.resize_all_caches()