From 3ee17585cd095e590096683395cfb9a017eac15e Mon Sep 17 00:00:00 2001
From: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>
Date: Fri, 16 Oct 2020 15:51:57 +0100
Subject: Make LruCache register its own metrics (#8561)

rather than have everything that instantiates an LruCache manage metrics
separately, have LruCache do it itself.
---
 synapse/util/caches/__init__.py | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

(limited to 'synapse/util/caches/__init__.py')

diff --git a/synapse/util/caches/__init__.py b/synapse/util/caches/__init__.py
index 8fc05be278..89f0b38535 100644
--- a/synapse/util/caches/__init__.py
+++ b/synapse/util/caches/__init__.py
@@ -16,7 +16,7 @@
 
 import logging
 from sys import intern
-from typing import Callable, Dict, Optional
+from typing import Callable, Dict, Optional, Sized
 
 import attr
 from prometheus_client.core import Gauge
@@ -92,7 +92,7 @@ class CacheMetric:
 def register_cache(
     cache_type: str,
     cache_name: str,
-    cache,
+    cache: Sized,
     collect_callback: Optional[Callable] = None,
     resizable: bool = True,
     resize_callback: Optional[Callable] = None,
@@ -100,12 +100,15 @@ def register_cache(
     """Register a cache object for metric collection and resizing.
 
     Args:
-        cache_type
+        cache_type: a string indicating the "type" of the cache. This is used
+            only for deduplication so isn't too important provided it's constant.
         cache_name: name of the cache
-        cache: cache itself
+        cache: cache itself, which must implement __len__(), and may optionally implement
+             a max_size property
         collect_callback: If given, a function which is called during metric
             collection to update additional metrics.
-        resizable: Whether this cache supports being resized.
+        resizable: Whether this cache supports being resized, in which case either
+            resize_callback must be provided, or the cache must support set_max_size().
         resize_callback: A function which can be called to resize the cache.
 
     Returns:
-- 
cgit 1.5.1