From 19dc676d1aaf66a45c9a1810132952f7ae3ca2aa Mon Sep 17 00:00:00 2001 From: Erik Johnston Date: Fri, 21 Sep 2018 16:25:42 +0100 Subject: [PATCH] Fix ExpiringCache.__len__ to be accurate It used to try and produce an estimate, which was sometimes negative. This caused metrics to be sad, so lets always just calculate it from scratch. --- synapse/util/caches/expiringcache.py | 21 +++++++++------------ 1 file changed, 9 insertions(+), 12 deletions(-) diff --git a/synapse/util/caches/expiringcache.py b/synapse/util/caches/expiringcache.py index 346669e4c..8ac56d85f 100644 --- a/synapse/util/caches/expiringcache.py +++ b/synapse/util/caches/expiringcache.py @@ -16,7 +16,7 @@ import logging from collections import OrderedDict -from six import iteritems +from six import iteritems, itervalues from synapse.metrics.background_process_metrics import run_as_background_process from synapse.util.caches import register_cache @@ -59,8 +59,6 @@ class ExpiringCache(object): self.iterable = iterable - self._size_estimate = 0 - self.metrics = register_cache("expiring", cache_name, self) if not self._expiry_ms: @@ -79,16 +77,11 @@ class ExpiringCache(object): now = self._clock.time_msec() self._cache[key] = _CacheEntry(now, value) - if self.iterable: - self._size_estimate += len(value) - # Evict if there are now too many items while self._max_len and len(self) > self._max_len: _key, value = self._cache.popitem(last=False) if self.iterable: - removed_len = len(value.value) - self.metrics.inc_evictions(removed_len) - self._size_estimate -= removed_len + self.metrics.inc_evictions(len(value.value)) else: self.metrics.inc_evictions() @@ -111,7 +104,9 @@ class ExpiringCache(object): return default if self.iterable: - self._size_estimate -= len(value.value) + self.metrics.inc_evictions(len(value.value)) + else: + self.metrics.inc_evictions() return value @@ -149,7 +144,9 @@ class ExpiringCache(object): for k in keys_to_delete: value = self._cache.pop(k) if self.iterable: - self._size_estimate -= len(value.value) + self.metrics.inc_evictions(len(value.value)) + else: + self.metrics.inc_evictions() logger.debug( "[%s] _prune_cache before: %d, after len: %d", @@ -158,7 +155,7 @@ class ExpiringCache(object): def __len__(self): if self.iterable: - return self._size_estimate + return sum(len(entry.value) for entry in itervalues(self._cache)) else: return len(self._cache)