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@@ -12,9 +12,13 @@
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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+import logging
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from synapse.util.async import ObservableDeferred
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from synapse.util.caches import metrics as cache_metrics
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+from synapse.util.logcontext import make_deferred_yieldable, run_in_background
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+
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+logger = logging.getLogger(__name__)
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class ResponseCache(object):
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@@ -31,6 +35,7 @@ class ResponseCache(object):
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self.clock = hs.get_clock()
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self.timeout_sec = timeout_ms / 1000.
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+ self._name = name
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self._metrics = cache_metrics.register_cache(
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"response_cache",
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size_callback=lambda: self.size(),
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@@ -47,7 +52,7 @@ class ResponseCache(object):
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so you'll probably want to make_deferred_yieldable it.
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Args:
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- key (str):
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+ key (hashable):
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Returns:
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twisted.internet.defer.Deferred|None: None if there is no entry
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@@ -76,7 +81,7 @@ class ResponseCache(object):
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to do it everywhere ResponseCache is used.)
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Args:
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- key (str):
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+ key (hashable):
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deferred (twisted.internet.defer.Deferred):
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Returns:
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@@ -97,3 +102,52 @@ class ResponseCache(object):
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result.addBoth(remove)
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return result.observe()
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+
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+ def wrap(self, key, callback, *args, **kwargs):
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+ """Wrap together a *get* and *set* call, taking care of logcontexts
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+
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+ First looks up the key in the cache, and if it is present makes it
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+ follow the synapse logcontext rules and returns it.
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+
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+ Otherwise, makes a call to *callback(*args, **kwargs)*, which should
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+ follow the synapse logcontext rules, and adds the result to the cache.
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+
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+ Example usage:
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+
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+ @defer.inlineCallbacks
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+ def handle_request(request):
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+ # etc
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+ defer.returnValue(result)
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+
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+ result = yield response_cache.wrap(
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+ key,
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+ handle_request,
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+ request,
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+ )
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+
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+ Args:
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+ key (hashable): key to get/set in the cache
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+
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+ callback (callable): function to call if the key is not found in
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+ the cache
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+
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+ *args: positional parameters to pass to the callback, if it is used
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+
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+ **kwargs: named paramters to pass to the callback, if it is used
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+
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+ Returns:
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+ twisted.internet.defer.Deferred: yieldable result
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+ """
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+ result = self.get(key)
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+ if not result:
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+ logger.info("[%s]: no cached result for [%s], calculating new one",
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+ self._name, key)
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+ d = run_in_background(callback, *args, **kwargs)
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+ result = self.set(key, d)
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+ elif result.called:
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+ logger.info("[%s]: using completed cached result for [%s]",
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+ self._name, key)
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+ else:
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+ logger.info("[%s]: using incomplete cached result for [%s]",
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+ self._name, key)
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+ return make_deferred_yieldable(result)
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