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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.
pull/3933/head
Erik Johnston 2018-09-21 16:25:42 +01:00
parent 5230bc1471
commit 19dc676d1a
1 changed files with 9 additions and 12 deletions
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21
synapse/util/caches/expiringcache.py
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@ -16,7 +16,7 @@
import logging import logging
from collections import OrderedDict 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.metrics.background_process_metrics import run_as_background_process
from synapse.util.caches import register_cache from synapse.util.caches import register_cache
@ -59,8 +59,6 @@ class ExpiringCache(object):
self.iterable = iterable self.iterable = iterable
self._size_estimate = 0
self.metrics = register_cache("expiring", cache_name, self) self.metrics = register_cache("expiring", cache_name, self)
if not self._expiry_ms: if not self._expiry_ms:
@ -79,16 +77,11 @@ class ExpiringCache(object):
now = self._clock.time_msec() now = self._clock.time_msec()
self._cache[key] = _CacheEntry(now, value) self._cache[key] = _CacheEntry(now, value)
if self.iterable:
self._size_estimate += len(value)
# Evict if there are now too many items # Evict if there are now too many items
while self._max_len and len(self) > self._max_len: while self._max_len and len(self) > self._max_len:
_key, value = self._cache.popitem(last=False) _key, value = self._cache.popitem(last=False)
if self.iterable: if self.iterable:
removed_len = len(value.value) self.metrics.inc_evictions(len(value.value))
self.metrics.inc_evictions(removed_len)
self._size_estimate -= removed_len
else: else:
self.metrics.inc_evictions() self.metrics.inc_evictions()
@ -111,7 +104,9 @@ class ExpiringCache(object):
return default return default
if self.iterable: if self.iterable:
self._size_estimate -= len(value.value) self.metrics.inc_evictions(len(value.value))
else:
self.metrics.inc_evictions()
return value return value
@ -149,7 +144,9 @@ class ExpiringCache(object):
for k in keys_to_delete: for k in keys_to_delete:
value = self._cache.pop(k) value = self._cache.pop(k)
if self.iterable: if self.iterable:
self._size_estimate -= len(value.value) self.metrics.inc_evictions(len(value.value))
else:
self.metrics.inc_evictions()
logger.debug( logger.debug(
"[%s] _prune_cache before: %d, after len: %d", "[%s] _prune_cache before: %d, after len: %d",
@ -158,7 +155,7 @@ class ExpiringCache(object):
def __len__(self): def __len__(self):
if self.iterable: if self.iterable:
return self._size_estimate return sum(len(entry.value) for entry in itervalues(self._cache))
else: else:
return len(self._cache) return len(self._cache)