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100 lines
3.3 KiB
Python
100 lines
3.3 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright 2016 OpenMarket Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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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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from synapse.util.async import ObservableDeferred
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from synapse.util.caches import metrics as cache_metrics
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class ResponseCache(object):
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"""
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This caches a deferred response. Until the deferred completes it will be
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returned from the cache. This means that if the client retries the request
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while the response is still being computed, that original response will be
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used rather than trying to compute a new response.
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"""
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def __init__(self, hs, name, timeout_ms=0):
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self.pending_result_cache = {} # Requests that haven't finished yet.
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self.clock = hs.get_clock()
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self.timeout_sec = timeout_ms / 1000.
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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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cache_name=name,
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)
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def size(self):
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return len(self.pending_result_cache)
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def get(self, key):
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"""Look up the given key.
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Returns a deferred which doesn't follow the synapse logcontext rules,
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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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Returns:
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twisted.internet.defer.Deferred|None: None if there is no entry
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for this key; otherwise a deferred result.
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"""
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result = self.pending_result_cache.get(key)
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if result is not None:
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self._metrics.inc_hits()
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return result.observe()
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else:
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self._metrics.inc_misses()
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return None
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def set(self, key, deferred):
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"""Set the entry for the given key to the given deferred.
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*deferred* should run its callbacks in the sentinel logcontext (ie,
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you should wrap normal synapse deferreds with
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logcontext.run_in_background).
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Returns a new Deferred which also doesn't follow the synapse logcontext
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rules, so you will want to make_deferred_yieldable it
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(TODO: before using this more widely, it might make sense to refactor
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it and get() so that they do the necessary wrapping rather than having
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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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deferred (twisted.internet.defer.Deferred):
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Returns:
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twisted.internet.defer.Deferred
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"""
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result = ObservableDeferred(deferred, consumeErrors=True)
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self.pending_result_cache[key] = result
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def remove(r):
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if self.timeout_sec:
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self.clock.call_later(
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self.timeout_sec,
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self.pending_result_cache.pop, key, None,
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)
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else:
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self.pending_result_cache.pop(key, None)
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return r
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result.addBoth(remove)
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return result.observe()
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