diff options
Diffstat (limited to 'synapse/util/caches')
| -rw-r--r-- | synapse/util/caches/descriptors.py | 64 | ||||
| -rw-r--r-- | synapse/util/caches/dictionary_cache.py | 6 | ||||
| -rw-r--r-- | synapse/util/caches/lrucache.py | 15 | ||||
| -rw-r--r-- | synapse/util/caches/response_cache.py | 106 |
4 files changed, 159 insertions, 32 deletions
diff --git a/synapse/util/caches/descriptors.py b/synapse/util/caches/descriptors.py index bf3a66eae4..68285a7594 100644 --- a/synapse/util/caches/descriptors.py +++ b/synapse/util/caches/descriptors.py @@ -1,5 +1,6 @@ # -*- coding: utf-8 -*- # Copyright 2015, 2016 OpenMarket Ltd +# Copyright 2018 New Vector Ltd # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. @@ -39,12 +40,11 @@ _CacheSentinel = object() class CacheEntry(object): __slots__ = [ - "deferred", "sequence", "callbacks", "invalidated" + "deferred", "callbacks", "invalidated" ] - def __init__(self, deferred, sequence, callbacks): + def __init__(self, deferred, callbacks): self.deferred = deferred - self.sequence = sequence self.callbacks = set(callbacks) self.invalidated = False @@ -62,7 +62,6 @@ class Cache(object): "max_entries", "name", "keylen", - "sequence", "thread", "metrics", "_pending_deferred_cache", @@ -80,7 +79,6 @@ class Cache(object): self.name = name self.keylen = keylen - self.sequence = 0 self.thread = None self.metrics = register_cache(name, self.cache) @@ -113,11 +111,10 @@ class Cache(object): callbacks = [callback] if callback else [] val = self._pending_deferred_cache.get(key, _CacheSentinel) if val is not _CacheSentinel: - if val.sequence == self.sequence: - val.callbacks.update(callbacks) - if update_metrics: - self.metrics.inc_hits() - return val.deferred + val.callbacks.update(callbacks) + if update_metrics: + self.metrics.inc_hits() + return val.deferred val = self.cache.get(key, _CacheSentinel, callbacks=callbacks) if val is not _CacheSentinel: @@ -137,12 +134,9 @@ class Cache(object): self.check_thread() entry = CacheEntry( deferred=value, - sequence=self.sequence, callbacks=callbacks, ) - entry.callbacks.update(callbacks) - existing_entry = self._pending_deferred_cache.pop(key, None) if existing_entry: existing_entry.invalidate() @@ -150,13 +144,25 @@ class Cache(object): self._pending_deferred_cache[key] = entry def shuffle(result): - if self.sequence == entry.sequence: - existing_entry = self._pending_deferred_cache.pop(key, None) - if existing_entry is entry: - self.cache.set(key, result, entry.callbacks) - else: - entry.invalidate() + existing_entry = self._pending_deferred_cache.pop(key, None) + if existing_entry is entry: + 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 + # updated, but it's possible that `set` was called without + # `invalidate` being previously called, in which case it may + # not have been. Either way, let's double-check now. entry.invalidate() return result @@ -168,25 +174,29 @@ class Cache(object): def invalidate(self, key): self.check_thread() + self.cache.pop(key, None) - # Increment the sequence number so that any SELECT statements that - # raced with the INSERT don't update the cache (SYN-369) - self.sequence += 1 + # if we have a pending lookup for this key, remove it from the + # _pending_deferred_cache, which will (a) stop it being returned + # for future queries and (b) stop it being persisted as a proper entry + # in self.cache. entry = self._pending_deferred_cache.pop(key, None) + + # run the invalidation callbacks now, rather than waiting for the + # deferred to resolve. if entry: entry.invalidate() - self.cache.pop(key, None) - def invalidate_many(self, key): self.check_thread() if not isinstance(key, tuple): raise TypeError( "The cache key must be a tuple not %r" % (type(key),) ) - self.sequence += 1 self.cache.del_multi(key) + # if we have a pending lookup for this key, remove it from the + # _pending_deferred_cache, as above entry_dict = self._pending_deferred_cache.pop(key, None) if entry_dict is not None: for entry in iterate_tree_cache_entry(entry_dict): @@ -194,8 +204,10 @@ class Cache(object): def invalidate_all(self): self.check_thread() - self.sequence += 1 self.cache.clear() + for entry in self._pending_deferred_cache.itervalues(): + entry.invalidate() + self._pending_deferred_cache.clear() class _CacheDescriptorBase(object): diff --git a/synapse/util/caches/dictionary_cache.py b/synapse/util/caches/dictionary_cache.py index d4105822b3..1709e8b429 100644 --- a/synapse/util/caches/dictionary_cache.py +++ b/synapse/util/caches/dictionary_cache.py @@ -132,9 +132,13 @@ class DictionaryCache(object): self._update_or_insert(key, value, known_absent) def _update_or_insert(self, key, value, known_absent): - entry = self.cache.setdefault(key, DictionaryEntry(False, set(), {})) + # We pop and reinsert as we need to tell the cache the size may have + # changed + + entry = self.cache.pop(key, DictionaryEntry(False, set(), {})) entry.value.update(value) entry.known_absent.update(known_absent) + self.cache[key] = entry def _insert(self, key, value, known_absent): self.cache[key] = DictionaryEntry(True, known_absent, value) diff --git a/synapse/util/caches/lrucache.py b/synapse/util/caches/lrucache.py index f088dd430e..1c5a982094 100644 --- a/synapse/util/caches/lrucache.py +++ b/synapse/util/caches/lrucache.py @@ -154,14 +154,21 @@ class LruCache(object): def cache_set(key, value, callbacks=[]): node = cache.get(key, None) if node is not None: - if value != node.value: + # We sometimes store large objects, e.g. dicts, which cause + # the inequality check to take a long time. So let's only do + # the check if we have some callbacks to call. + if node.callbacks and value != node.value: for cb in node.callbacks: cb() node.callbacks.clear() - if size_callback: - cached_cache_len[0] -= size_callback(node.value) - cached_cache_len[0] += size_callback(value) + # We don't bother to protect this by value != node.value as + # generally size_callback will be cheap compared with equality + # checks. (For example, taking the size of two dicts is quicker + # than comparing them for equality.) + if size_callback: + cached_cache_len[0] -= size_callback(node.value) + cached_cache_len[0] += size_callback(value) node.callbacks.update(callbacks) diff --git a/synapse/util/caches/response_cache.py b/synapse/util/caches/response_cache.py index 00af539880..7f79333e96 100644 --- a/synapse/util/caches/response_cache.py +++ b/synapse/util/caches/response_cache.py @@ -12,8 +12,15 @@ # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. +import logging + +from twisted.internet import defer from synapse.util.async import ObservableDeferred +from synapse.util.caches import metrics as cache_metrics +from synapse.util.logcontext import make_deferred_yieldable, run_in_background + +logger = logging.getLogger(__name__) class ResponseCache(object): @@ -24,20 +31,68 @@ class ResponseCache(object): used rather than trying to compute a new response. """ - def __init__(self, hs, timeout_ms=0): + def __init__(self, hs, name, timeout_ms=0): self.pending_result_cache = {} # Requests that haven't finished yet. self.clock = hs.get_clock() self.timeout_sec = timeout_ms / 1000. + self._name = name + self._metrics = cache_metrics.register_cache( + "response_cache", + size_callback=lambda: self.size(), + cache_name=name, + ) + + def size(self): + return len(self.pending_result_cache) + def get(self, key): + """Look up the given key. + + Can return either a new Deferred (which also doesn't follow the synapse + logcontext rules), or, if the request has completed, the actual + result. You will probably want to make_deferred_yieldable the result. + + If there is no entry for the key, returns None. It is worth noting that + this means there is no way to distinguish a completed result of None + from an absent cache entry. + + Args: + key (hashable): + + Returns: + twisted.internet.defer.Deferred|None|E: None if there is no entry + for this key; otherwise either a deferred result or the result + itself. + """ result = self.pending_result_cache.get(key) if result is not None: + self._metrics.inc_hits() return result.observe() else: + self._metrics.inc_misses() return None def set(self, key, deferred): + """Set the entry for the given key to the given deferred. + + *deferred* should run its callbacks in the sentinel logcontext (ie, + you should wrap normal synapse deferreds with + logcontext.run_in_background). + + Can return either a new Deferred (which also doesn't follow the synapse + logcontext rules), or, if *deferred* was already complete, the actual + result. You will probably want to make_deferred_yieldable the result. + + Args: + key (hashable): + deferred (twisted.internet.defer.Deferred[T): + + Returns: + twisted.internet.defer.Deferred[T]|T: a new deferred, or the actual + result. + """ result = ObservableDeferred(deferred, consumeErrors=True) self.pending_result_cache[key] = result @@ -53,3 +108,52 @@ class ResponseCache(object): result.addBoth(remove) return result.observe() + + def wrap(self, key, callback, *args, **kwargs): + """Wrap together a *get* and *set* call, taking care of logcontexts + + First looks up the key in the cache, and if it is present makes it + follow the synapse logcontext rules and returns it. + + Otherwise, makes a call to *callback(*args, **kwargs)*, which should + follow the synapse logcontext rules, and adds the result to the cache. + + Example usage: + + @defer.inlineCallbacks + def handle_request(request): + # etc + defer.returnValue(result) + + result = yield response_cache.wrap( + key, + handle_request, + request, + ) + + Args: + key (hashable): key to get/set in the cache + + callback (callable): function to call if the key is not found in + the cache + + *args: positional parameters to pass to the callback, if it is used + + **kwargs: named paramters to pass to the callback, if it is used + + Returns: + twisted.internet.defer.Deferred: yieldable result + """ + result = self.get(key) + if not result: + logger.info("[%s]: no cached result for [%s], calculating new one", + self._name, key) + d = run_in_background(callback, *args, **kwargs) + result = self.set(key, d) + elif not isinstance(result, defer.Deferred) or result.called: + logger.info("[%s]: using completed cached result for [%s]", + self._name, key) + else: + logger.info("[%s]: using incomplete cached result for [%s]", + self._name, key) + return make_deferred_yieldable(result) |