mirror of https://github.com/watcha-fr/synapse
Erik Johnston
6 years ago
parent
af9f1c0764
commit
107ad133fc
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# -*- coding: utf-8 -*- |
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# Copyright 2019 The Matrix.org Foundation C.I.C. |
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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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|
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import json |
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import logging |
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import random |
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import time |
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import attr |
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from twisted.internet import defer |
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from twisted.web.client import RedirectAgent, readBody |
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from twisted.web.http import stringToDatetime |
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from synapse.logging.context import make_deferred_yieldable |
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from synapse.util import Clock |
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from synapse.util.caches.ttlcache import TTLCache |
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from synapse.util.metrics import Measure |
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# period to cache .well-known results for by default |
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WELL_KNOWN_DEFAULT_CACHE_PERIOD = 24 * 3600 |
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# jitter to add to the .well-known default cache ttl |
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WELL_KNOWN_DEFAULT_CACHE_PERIOD_JITTER = 10 * 60 |
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# period to cache failure to fetch .well-known for |
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WELL_KNOWN_INVALID_CACHE_PERIOD = 1 * 3600 |
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# cap for .well-known cache period |
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WELL_KNOWN_MAX_CACHE_PERIOD = 48 * 3600 |
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# lower bound for .well-known cache period |
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WELL_KNOWN_MIN_CACHE_PERIOD = 5 * 60 |
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logger = logging.getLogger(__name__) |
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@attr.s(slots=True, frozen=True) |
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class WellKnownLookupResult(object): |
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delegated_server = attr.ib() |
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class WellKnownResolver(object): |
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"""Handles well-known lookups for matrix servers. |
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""" |
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def __init__(self, reactor, agent, well_known_cache=None): |
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self._reactor = reactor |
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self._clock = Clock(reactor) |
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if well_known_cache is None: |
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well_known_cache = TTLCache("well-known") |
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self._well_known_cache = well_known_cache |
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self._well_known_agent = RedirectAgent(agent) |
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@defer.inlineCallbacks |
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def get_well_known(self, server_name): |
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"""Attempt to fetch and parse a .well-known file for the given server |
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Args: |
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server_name (bytes): name of the server, from the requested url |
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Returns: |
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Deferred[WellKnownLookupResult]: The result of the lookup |
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""" |
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try: |
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result = self._well_known_cache[server_name] |
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except KeyError: |
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# TODO: should we linearise so that we don't end up doing two .well-known |
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# requests for the same server in parallel? |
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with Measure(self._clock, "get_well_known"): |
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result, cache_period = yield self._do_get_well_known(server_name) |
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if cache_period > 0: |
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self._well_known_cache.set(server_name, result, cache_period) |
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return WellKnownLookupResult(delegated_server=result) |
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@defer.inlineCallbacks |
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def _do_get_well_known(self, server_name): |
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"""Actually fetch and parse a .well-known, without checking the cache |
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Args: |
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server_name (bytes): name of the server, from the requested url |
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Returns: |
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Deferred[Tuple[bytes|None|object],int]: |
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result, cache period, where result is one of: |
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- the new server name from the .well-known (as a `bytes`) |
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- None if there was no .well-known file. |
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- INVALID_WELL_KNOWN if the .well-known was invalid |
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""" |
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uri = b"https://%s/.well-known/matrix/server" % (server_name,) |
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uri_str = uri.decode("ascii") |
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logger.info("Fetching %s", uri_str) |
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try: |
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response = yield make_deferred_yieldable( |
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self._well_known_agent.request(b"GET", uri) |
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) |
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body = yield make_deferred_yieldable(readBody(response)) |
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if response.code != 200: |
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raise Exception("Non-200 response %s" % (response.code,)) |
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parsed_body = json.loads(body.decode("utf-8")) |
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logger.info("Response from .well-known: %s", parsed_body) |
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if not isinstance(parsed_body, dict): |
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raise Exception("not a dict") |
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if "m.server" not in parsed_body: |
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raise Exception("Missing key 'm.server'") |
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except Exception as e: |
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logger.info("Error fetching %s: %s", uri_str, e) |
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# add some randomness to the TTL to avoid a stampeding herd every hour |
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# after startup |
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cache_period = WELL_KNOWN_INVALID_CACHE_PERIOD |
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cache_period += random.uniform(0, WELL_KNOWN_DEFAULT_CACHE_PERIOD_JITTER) |
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return (None, cache_period) |
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result = parsed_body["m.server"].encode("ascii") |
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cache_period = _cache_period_from_headers( |
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response.headers, time_now=self._reactor.seconds |
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) |
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if cache_period is None: |
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cache_period = WELL_KNOWN_DEFAULT_CACHE_PERIOD |
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# add some randomness to the TTL to avoid a stampeding herd every 24 hours |
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# after startup |
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cache_period += random.uniform(0, WELL_KNOWN_DEFAULT_CACHE_PERIOD_JITTER) |
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else: |
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cache_period = min(cache_period, WELL_KNOWN_MAX_CACHE_PERIOD) |
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cache_period = max(cache_period, WELL_KNOWN_MIN_CACHE_PERIOD) |
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return (result, cache_period) |
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def _cache_period_from_headers(headers, time_now=time.time): |
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cache_controls = _parse_cache_control(headers) |
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if b"no-store" in cache_controls: |
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return 0 |
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if b"max-age" in cache_controls: |
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try: |
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max_age = int(cache_controls[b"max-age"]) |
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return max_age |
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except ValueError: |
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pass |
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expires = headers.getRawHeaders(b"expires") |
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if expires is not None: |
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try: |
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expires_date = stringToDatetime(expires[-1]) |
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return expires_date - time_now() |
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except ValueError: |
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# RFC7234 says 'A cache recipient MUST interpret invalid date formats, |
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# especially the value "0", as representing a time in the past (i.e., |
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# "already expired"). |
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return 0 |
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return None |
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def _parse_cache_control(headers): |
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cache_controls = {} |
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for hdr in headers.getRawHeaders(b"cache-control", []): |
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for directive in hdr.split(b","): |
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splits = [x.strip() for x in directive.split(b"=", 1)] |
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k = splits[0].lower() |
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v = splits[1] if len(splits) > 1 else None |
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cache_controls[k] = v |
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return cache_controls |
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