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Fix ExpiringCache.__len__ to be accurate

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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.
This commit is contained in:
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
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)