129 lines
5.1 KiB
Python
129 lines
5.1 KiB
Python
# 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 typing import TYPE_CHECKING, Awaitable, Callable, Dict, Hashable, Tuple
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from typing_extensions import ParamSpec
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from twisted.internet.defer import Deferred
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from twisted.python.failure import Failure
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from twisted.web.iweb import IRequest
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from synapse.logging.context import make_deferred_yieldable, run_in_background
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from synapse.types import JsonDict, Requester
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from synapse.util.async_helpers import ObservableDeferred
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if TYPE_CHECKING:
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from synapse.server import HomeServer
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logger = logging.getLogger(__name__)
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CLEANUP_PERIOD_MS = 1000 * 60 * 30 # 30 mins
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P = ParamSpec("P")
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class HttpTransactionCache:
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def __init__(self, hs: "HomeServer"):
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self.hs = hs
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self.clock = self.hs.get_clock()
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# $txn_key: (ObservableDeferred<(res_code, res_json_body)>, timestamp)
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self.transactions: Dict[
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Hashable, Tuple[ObservableDeferred[Tuple[int, JsonDict]], int]
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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 _get_transaction_key(self, request: IRequest, requester: Requester) -> Hashable:
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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 attributes from the requester: the access_token_id for regular users,
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the user ID for guest users, and the appservice ID for appservice users.
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Args:
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request: The incoming request.
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requester: The requester doing the request.
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Returns:
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A transaction key
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"""
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assert request.path is not None
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path: str = request.path.decode("utf8")
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if requester.is_guest:
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assert requester.user is not None, "Guest requester must have a user ID set"
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return (path, "guest", requester.user)
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elif requester.app_service is not None:
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return (path, "appservice", requester.app_service.id)
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else:
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assert (
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requester.access_token_id is not None
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), "Requester must have an access_token_id"
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return (path, "user", requester.access_token_id)
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def fetch_or_execute_request(
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self,
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request: IRequest,
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requester: Requester,
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fn: Callable[P, Awaitable[Tuple[int, JsonDict]]],
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*args: P.args,
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**kwargs: P.kwargs,
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) -> "Deferred[Tuple[int, JsonDict]]":
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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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request:
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requester:
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fn: A function which returns a tuple of (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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txn_key = self._get_transaction_key(request, requester)
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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: Failure) -> None:
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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) -> None:
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now = self.clock.time_msec()
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for key in list(self.transactions):
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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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