111 lines
4.2 KiB
Python
111 lines
4.2 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright 2014-2016 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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"""This module contains logic for storing HTTP PUT transactions. This is used
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to ensure idempotency when performing PUTs using the REST API."""
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import logging
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from synapse.api.auth import get_access_token_from_request
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from synapse.util.async import ObservableDeferred
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from synapse.util.logcontext import make_deferred_yieldable, run_in_background
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logger = logging.getLogger(__name__)
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def get_transaction_key(request):
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"""A helper function which returns a transaction key that can be used
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with TransactionCache for idempotent requests.
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Idempotency is based on the returned key being the same for separate
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requests to the same endpoint. The key is formed from the HTTP request
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path and the access_token for the requesting user.
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Args:
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request (twisted.web.http.Request): The incoming request. Must
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contain an access_token.
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Returns:
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str: A transaction key
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"""
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token = get_access_token_from_request(request)
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return request.path + "/" + token
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CLEANUP_PERIOD_MS = 1000 * 60 * 30 # 30 mins
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class HttpTransactionCache(object):
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def __init__(self, clock):
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self.clock = clock
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self.transactions = {
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# $txn_key: (ObservableDeferred<(res_code, res_json_body)>, timestamp)
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}
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# Try to clean entries every 30 mins. This means entries will exist
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# for at *LEAST* 30 mins, and at *MOST* 60 mins.
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self.cleaner = self.clock.looping_call(self._cleanup, CLEANUP_PERIOD_MS)
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def fetch_or_execute_request(self, request, fn, *args, **kwargs):
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"""A helper function for fetch_or_execute which extracts
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a transaction key from the given request.
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See:
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fetch_or_execute
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"""
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return self.fetch_or_execute(
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get_transaction_key(request), fn, *args, **kwargs
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)
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def fetch_or_execute(self, txn_key, fn, *args, **kwargs):
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"""Fetches the response for this transaction, or executes the given function
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to produce a response for this transaction.
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Args:
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txn_key (str): A key to ensure idempotency should fetch_or_execute be
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called again at a later point in time.
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fn (function): A function which returns a tuple of
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(response_code, response_dict).
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*args: Arguments to pass to fn.
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**kwargs: Keyword arguments to pass to fn.
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Returns:
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Deferred which resolves to a tuple of (response_code, response_dict).
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"""
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if txn_key in self.transactions:
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observable = self.transactions[txn_key][0]
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else:
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# execute the function instead.
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deferred = run_in_background(fn, *args, **kwargs)
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observable = ObservableDeferred(deferred)
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self.transactions[txn_key] = (observable, self.clock.time_msec())
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# if the request fails with an exception, remove it
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# from the transaction map. This is done to ensure that we don't
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# cache transient errors like rate-limiting errors, etc.
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def remove_from_map(err):
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self.transactions.pop(txn_key, None)
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# we deliberately do not propagate the error any further, as we
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# expect the observers to have reported it.
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deferred.addErrback(remove_from_map)
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return make_deferred_yieldable(observable.observe())
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def _cleanup(self):
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now = self.clock.time_msec()
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for key in self.transactions.keys():
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ts = self.transactions[key][1]
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if now > (ts + CLEANUP_PERIOD_MS): # after cleanup period
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del self.transactions[key]
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