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author | Richard van der Hoff <richard@matrix.org> | 2018-04-12 12:08:59 +0100 |
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committer | Richard van der Hoff <richard@matrix.org> | 2018-04-12 13:02:15 +0100 |
commit | b78395b7fe449d59a5c46c81a869f9f191cd934f (patch) | |
tree | 3242266e7cafff4c6fc4084438d00f9a9025ee47 /synapse/util/caches | |
parent | Merge pull request #3092 from matrix-org/rav/response_cache_metrics (diff) | |
download | synapse-b78395b7fe449d59a5c46c81a869f9f191cd934f.tar.xz |
Refactor ResponseCache usage
Adds a `.wrap` method to ResponseCache which wraps up the boilerplate of a (get, set) pair, and then use it throughout the codebase. This will be largely non-functional, but does include the following functional changes: * federation_server.on_context_state_request: drops use of _server_linearizer which looked redundant and could cause incorrect cache misses by yielding between the get and the set. * RoomListHandler.get_remote_public_room_list(): fixes logcontext leaks * the wrap function includes some logging. I'm hoping this won't be too noisy on production.
Diffstat (limited to 'synapse/util/caches')
-rw-r--r-- | synapse/util/caches/response_cache.py | 58 |
1 files changed, 56 insertions, 2 deletions
diff --git a/synapse/util/caches/response_cache.py b/synapse/util/caches/response_cache.py index 066fa423fd..0c2c347953 100644 --- a/synapse/util/caches/response_cache.py +++ b/synapse/util/caches/response_cache.py @@ -12,9 +12,13 @@ # 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 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): @@ -31,6 +35,7 @@ class ResponseCache(object): 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(), @@ -47,7 +52,7 @@ class ResponseCache(object): so you'll probably want to make_deferred_yieldable it. Args: - key (str): + key (hashable): Returns: twisted.internet.defer.Deferred|None: None if there is no entry @@ -76,7 +81,7 @@ class ResponseCache(object): to do it everywhere ResponseCache is used.) Args: - key (str): + key (hashable): deferred (twisted.internet.defer.Deferred): Returns: @@ -97,3 +102,52 @@ 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 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) |