diff options
Diffstat (limited to 'synapse/util/caches/descriptors.py')
| -rw-r--r-- | synapse/util/caches/descriptors.py | 94 |
1 files changed, 60 insertions, 34 deletions
diff --git a/synapse/util/caches/descriptors.py b/synapse/util/caches/descriptors.py index 675db2f448..43f66ec4be 100644 --- a/synapse/util/caches/descriptors.py +++ b/synapse/util/caches/descriptors.py @@ -19,8 +19,9 @@ import logging import threading from collections import namedtuple -import six -from six import itervalues, string_types +from six import itervalues + +from prometheus_client import Gauge from twisted.internet import defer @@ -30,13 +31,18 @@ from synapse.util.async_helpers import ObservableDeferred from synapse.util.caches import get_cache_factor_for from synapse.util.caches.lrucache import LruCache from synapse.util.caches.treecache import TreeCache, iterate_tree_cache_entry -from synapse.util.stringutils import to_ascii from . import register_cache logger = logging.getLogger(__name__) +cache_pending_metric = Gauge( + "synapse_util_caches_cache_pending", + "Number of lookups currently pending for this cache", + ["name"], +) + _CacheSentinel = object() @@ -82,11 +88,19 @@ class Cache(object): self.name = name self.keylen = keylen self.thread = None - self.metrics = register_cache("cache", name, self.cache) + self.metrics = register_cache( + "cache", + name, + self.cache, + collect_callback=self._metrics_collection_callback, + ) def _on_evicted(self, evicted_count): self.metrics.inc_evictions(evicted_count) + def _metrics_collection_callback(self): + cache_pending_metric.labels(self.name).set(len(self._pending_deferred_cache)) + def check_thread(self): expected_thread = self.thread if expected_thread is None: @@ -108,7 +122,7 @@ class Cache(object): update_metrics (bool): whether to update the cache hit rate metrics Returns: - Either a Deferred or the raw result + Either an ObservableDeferred or the raw result """ callbacks = [callback] if callback else [] val = self._pending_deferred_cache.get(key, _CacheSentinel) @@ -132,9 +146,14 @@ class Cache(object): return default def set(self, key, value, callback=None): + if not isinstance(value, defer.Deferred): + raise TypeError("not a Deferred") + callbacks = [callback] if callback else [] self.check_thread() - entry = CacheEntry(deferred=value, callbacks=callbacks) + observable = ObservableDeferred(value, consumeErrors=True) + observer = defer.maybeDeferred(observable.observe) + entry = CacheEntry(deferred=observable, callbacks=callbacks) existing_entry = self._pending_deferred_cache.pop(key, None) if existing_entry: @@ -142,20 +161,31 @@ class Cache(object): self._pending_deferred_cache[key] = entry - def shuffle(result): + def compare_and_pop(): + """Check if our entry is still the one in _pending_deferred_cache, and + if so, pop it. + + Returns true if the entries matched. + """ existing_entry = self._pending_deferred_cache.pop(key, None) if existing_entry is entry: + return True + + # oops, the _pending_deferred_cache has been updated since + # we started our query, so we are out of date. + # + # Better put back whatever we took out. (We do it this way + # round, rather than peeking into the _pending_deferred_cache + # and then removing on a match, to make the common case faster) + if existing_entry is not None: + self._pending_deferred_cache[key] = existing_entry + + return False + + def cb(result): + if compare_and_pop(): self.cache.set(key, result, entry.callbacks) else: - # oops, the _pending_deferred_cache has been updated since - # we started our query, so we are out of date. - # - # Better put back whatever we took out. (We do it this way - # round, rather than peeking into the _pending_deferred_cache - # and then removing on a match, to make the common case faster) - if existing_entry is not None: - self._pending_deferred_cache[key] = existing_entry - # we're not going to put this entry into the cache, so need # to make sure that the invalidation callbacks are called. # That was probably done when _pending_deferred_cache was @@ -163,9 +193,16 @@ class Cache(object): # `invalidate` being previously called, in which case it may # not have been. Either way, let's double-check now. entry.invalidate() - return result - entry.deferred.addCallback(shuffle) + def eb(_fail): + compare_and_pop() + entry.invalidate() + + # once the deferred completes, we can move the entry from the + # _pending_deferred_cache to the real cache. + # + observer.addCallbacks(cb, eb) + return observable def prefill(self, key, value, callback=None): callbacks = [callback] if callback else [] @@ -289,7 +326,7 @@ class CacheDescriptor(_CacheDescriptorBase): def foo(self, key, cache_context): r1 = yield self.bar1(key, on_invalidate=cache_context.invalidate) r2 = yield self.bar2(key, on_invalidate=cache_context.invalidate) - defer.returnValue(r1 + r2) + return r1 + r2 Args: num_args (int): number of positional arguments (excluding ``self`` and @@ -398,20 +435,10 @@ class CacheDescriptor(_CacheDescriptorBase): ret.addErrback(onErr) - # If our cache_key is a string on py2, try to convert to ascii - # to save a bit of space in large caches. Py3 does this - # internally automatically. - if six.PY2 and isinstance(cache_key, string_types): - cache_key = to_ascii(cache_key) - - result_d = ObservableDeferred(ret, consumeErrors=True) - cache.set(cache_key, result_d, callback=invalidate_callback) + result_d = cache.set(cache_key, ret, callback=invalidate_callback) observer = result_d.observe() - if isinstance(observer, defer.Deferred): - return make_deferred_yieldable(observer) - else: - return observer + return make_deferred_yieldable(observer) if self.num_args == 1: wrapped.invalidate = lambda key: cache.invalidate(key[0]) @@ -527,7 +554,7 @@ class CacheListDescriptor(_CacheDescriptorBase): missing.add(arg) if missing: - # we need an observable deferred for each entry in the list, + # we need a deferred for each entry in the list, # which we put in the cache. Each deferred resolves with the # relevant result for that key. deferreds_map = {} @@ -535,8 +562,7 @@ class CacheListDescriptor(_CacheDescriptorBase): deferred = defer.Deferred() deferreds_map[arg] = deferred key = arg_to_cache_key(arg) - observable = ObservableDeferred(deferred) - cache.set(key, observable, callback=invalidate_callback) + cache.set(key, deferred, callback=invalidate_callback) def complete_all(res): # the wrapped function has completed. It returns a |