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Merge pull request #5836 from matrix-org/erikj/lower_bound_ttl_well_known 

Add a lower bound to well-known TTL.
This commit is contained in:
Erik Johnston 2019-08-13 12:41:16 +01:00 committed by GitHub
parent 2546f32b90 f218705d2a
commit e9906b0772
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GPG Key ID: 4AEE18F83AFDEB23
4 changed files with 222 additions and 171 deletions
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1
changelog.d/5836.misc Normal file
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@ -0,0 +1 @@
Add a lower bound to well-known lookup cache time to avoid repeated lookups.

162
synapse/http/federation/matrix_federation_agent.py
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@ -12,10 +12,8 @@
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import json
import logging
import random
import time
import attr
from netaddr import IPAddress
@ -24,31 +22,16 @@ from zope.interface import implementer
from twisted.internet import defer
from twisted.internet.endpoints import HostnameEndpoint, wrapClientTLS
from twisted.internet.interfaces import IStreamClientEndpoint
from twisted.web.client import URI, Agent, HTTPConnectionPool, RedirectAgent, readBody
from twisted.web.http import stringToDatetime
from twisted.web.client import URI, Agent, HTTPConnectionPool
from twisted.web.http_headers import Headers
from twisted.web.iweb import IAgent
from synapse.http.federation.srv_resolver import SrvResolver, pick_server_from_list
from synapse.http.federation.well_known_resolver import WellKnownResolver
from synapse.logging.context import make_deferred_yieldable
from synapse.util import Clock
from synapse.util.caches.ttlcache import TTLCache
from synapse.util.metrics import Measure
# period to cache .well-known results for by default
WELL_KNOWN_DEFAULT_CACHE_PERIOD = 24 * 3600
# jitter to add to the .well-known default cache ttl
WELL_KNOWN_DEFAULT_CACHE_PERIOD_JITTER = 10 * 60
# period to cache failure to fetch .well-known for
WELL_KNOWN_INVALID_CACHE_PERIOD = 1 * 3600
# cap for .well-known cache period
WELL_KNOWN_MAX_CACHE_PERIOD = 48 * 3600
logger = logging.getLogger(__name__)
well_known_cache = TTLCache("well-known")
@implementer(IAgent)
@ -78,7 +61,7 @@ class MatrixFederationAgent(object):
reactor,
tls_client_options_factory,
_srv_resolver=None,
_well_known_cache=well_known_cache,
_well_known_cache=None,
):
self._reactor = reactor
self._clock = Clock(reactor)
@ -93,20 +76,15 @@ class MatrixFederationAgent(object):
self._pool.maxPersistentPerHost = 5
self._pool.cachedConnectionTimeout = 2 * 60
_well_known_agent = RedirectAgent(
Agent(
self._well_known_resolver = WellKnownResolver(
self._reactor,
agent=Agent(
self._reactor,
pool=self._pool,
contextFactory=tls_client_options_factory,
)
),
well_known_cache=_well_known_cache,
)
self._well_known_agent = _well_known_agent
# our cache of .well-known lookup results, mapping from server name
# to delegated name. The values can be:
# `bytes`: a valid server-name
# `None`: there is no (valid) .well-known here
self._well_known_cache = _well_known_cache
@defer.inlineCallbacks
def request(self, method, uri, headers=None, bodyProducer=None):
@ -217,7 +195,10 @@ class MatrixFederationAgent(object):
if lookup_well_known:
# try a .well-known lookup
well_known_server = yield self._get_well_known(parsed_uri.host)
well_known_result = yield self._well_known_resolver.get_well_known(
parsed_uri.host
)
well_known_server = well_known_result.delegated_server
if well_known_server:
# if we found a .well-known, start again, but don't do another
@ -280,85 +261,6 @@ class MatrixFederationAgent(object):
target_port=port,
)
@defer.inlineCallbacks
def _get_well_known(self, server_name):
"""Attempt to fetch and parse a .well-known file for the given server
Args:
server_name (bytes): name of the server, from the requested url
Returns:
Deferred[bytes|None]: either the new server name, from the .well-known, or
None if there was no .well-known file.
"""
try:
result = self._well_known_cache[server_name]
except KeyError:
# TODO: should we linearise so that we don't end up doing two .well-known
# requests for the same server in parallel?
with Measure(self._clock, "get_well_known"):
result, cache_period = yield self._do_get_well_known(server_name)
if cache_period > 0:
self._well_known_cache.set(server_name, result, cache_period)
return result
@defer.inlineCallbacks
def _do_get_well_known(self, server_name):
"""Actually fetch and parse a .well-known, without checking the cache
Args:
server_name (bytes): name of the server, from the requested url
Returns:
Deferred[Tuple[bytes|None|object],int]:
result, cache period, where result is one of:
- the new server name from the .well-known (as a `bytes`)
- None if there was no .well-known file.
- INVALID_WELL_KNOWN if the .well-known was invalid
"""
uri = b"https://%s/.well-known/matrix/server" % (server_name,)
uri_str = uri.decode("ascii")
logger.info("Fetching %s", uri_str)
try:
response = yield make_deferred_yieldable(
self._well_known_agent.request(b"GET", uri)
)
body = yield make_deferred_yieldable(readBody(response))
if response.code != 200:
raise Exception("Non-200 response %s" % (response.code,))
parsed_body = json.loads(body.decode("utf-8"))
logger.info("Response from .well-known: %s", parsed_body)
if not isinstance(parsed_body, dict):
raise Exception("not a dict")
if "m.server" not in parsed_body:
raise Exception("Missing key 'm.server'")
except Exception as e:
logger.info("Error fetching %s: %s", uri_str, e)
# add some randomness to the TTL to avoid a stampeding herd every hour
# after startup
cache_period = WELL_KNOWN_INVALID_CACHE_PERIOD
cache_period += random.uniform(0, WELL_KNOWN_DEFAULT_CACHE_PERIOD_JITTER)
return (None, cache_period)
result = parsed_body["m.server"].encode("ascii")
cache_period = _cache_period_from_headers(
response.headers, time_now=self._reactor.seconds
)
if cache_period is None:
cache_period = WELL_KNOWN_DEFAULT_CACHE_PERIOD
# add some randomness to the TTL to avoid a stampeding herd every 24 hours
# after startup
cache_period += random.uniform(0, WELL_KNOWN_DEFAULT_CACHE_PERIOD_JITTER)
else:
cache_period = min(cache_period, WELL_KNOWN_MAX_CACHE_PERIOD)
return (result, cache_period)
@implementer(IStreamClientEndpoint)
class LoggingHostnameEndpoint(object):
@ -374,44 +276,6 @@ class LoggingHostnameEndpoint(object):
return self.ep.connect(protocol_factory)
def _cache_period_from_headers(headers, time_now=time.time):
cache_controls = _parse_cache_control(headers)
if b"no-store" in cache_controls:
return 0
if b"max-age" in cache_controls:
try:
max_age = int(cache_controls[b"max-age"])
return max_age
except ValueError:
pass
expires = headers.getRawHeaders(b"expires")
if expires is not None:
try:
expires_date = stringToDatetime(expires[-1])
return expires_date - time_now()
except ValueError:
# RFC7234 says 'A cache recipient MUST interpret invalid date formats,
# especially the value "0", as representing a time in the past (i.e.,
# "already expired").
return 0
return None
def _parse_cache_control(headers):
cache_controls = {}
for hdr in headers.getRawHeaders(b"cache-control", []):
for directive in hdr.split(b","):
splits = [x.strip() for x in directive.split(b"=", 1)]
k = splits[0].lower()
v = splits[1] if len(splits) > 1 else None
cache_controls[k] = v
return cache_controls
@attr.s
class _RoutingResult(object):
"""The result returned by `_route_matrix_uri`.

187
synapse/http/federation/well_known_resolver.py Normal file
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@ -0,0 +1,187 @@
# -*- coding: utf-8 -*-
# Copyright 2019 The Matrix.org Foundation C.I.C.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import json
import logging
import random
import time
import attr
from twisted.internet import defer
from twisted.web.client import RedirectAgent, readBody
from twisted.web.http import stringToDatetime
from synapse.logging.context import make_deferred_yieldable
from synapse.util import Clock
from synapse.util.caches.ttlcache import TTLCache
from synapse.util.metrics import Measure
# period to cache .well-known results for by default
WELL_KNOWN_DEFAULT_CACHE_PERIOD = 24 * 3600
# jitter to add to the .well-known default cache ttl
WELL_KNOWN_DEFAULT_CACHE_PERIOD_JITTER = 10 * 60
# period to cache failure to fetch .well-known for
WELL_KNOWN_INVALID_CACHE_PERIOD = 1 * 3600
# cap for .well-known cache period
WELL_KNOWN_MAX_CACHE_PERIOD = 48 * 3600
# lower bound for .well-known cache period
WELL_KNOWN_MIN_CACHE_PERIOD = 5 * 60
logger = logging.getLogger(__name__)
_well_known_cache = TTLCache("well-known")
@attr.s(slots=True, frozen=True)
class WellKnownLookupResult(object):
delegated_server = attr.ib()
class WellKnownResolver(object):
"""Handles well-known lookups for matrix servers.
"""
def __init__(self, reactor, agent, well_known_cache=None):
self._reactor = reactor
self._clock = Clock(reactor)
if well_known_cache is None:
well_known_cache = _well_known_cache
self._well_known_cache = well_known_cache
self._well_known_agent = RedirectAgent(agent)
@defer.inlineCallbacks
def get_well_known(self, server_name):
"""Attempt to fetch and parse a .well-known file for the given server
Args:
server_name (bytes): name of the server, from the requested url
Returns:
Deferred[WellKnownLookupResult]: The result of the lookup
"""
try:
result = self._well_known_cache[server_name]
except KeyError:
# TODO: should we linearise so that we don't end up doing two .well-known
# requests for the same server in parallel?
with Measure(self._clock, "get_well_known"):
result, cache_period = yield self._do_get_well_known(server_name)
if cache_period > 0:
self._well_known_cache.set(server_name, result, cache_period)
return WellKnownLookupResult(delegated_server=result)
@defer.inlineCallbacks
def _do_get_well_known(self, server_name):
"""Actually fetch and parse a .well-known, without checking the cache
Args:
server_name (bytes): name of the server, from the requested url
Returns:
Deferred[Tuple[bytes|None|object],int]:
result, cache period, where result is one of:
- the new server name from the .well-known (as a `bytes`)
- None if there was no .well-known file.
- INVALID_WELL_KNOWN if the .well-known was invalid
"""
uri = b"https://%s/.well-known/matrix/server" % (server_name,)
uri_str = uri.decode("ascii")
logger.info("Fetching %s", uri_str)
try:
response = yield make_deferred_yieldable(
self._well_known_agent.request(b"GET", uri)
)
body = yield make_deferred_yieldable(readBody(response))
if response.code != 200:
raise Exception("Non-200 response %s" % (response.code,))
parsed_body = json.loads(body.decode("utf-8"))
logger.info("Response from .well-known: %s", parsed_body)
if not isinstance(parsed_body, dict):
raise Exception("not a dict")
if "m.server" not in parsed_body:
raise Exception("Missing key 'm.server'")
except Exception as e:
logger.info("Error fetching %s: %s", uri_str, e)
# add some randomness to the TTL to avoid a stampeding herd every hour
# after startup
cache_period = WELL_KNOWN_INVALID_CACHE_PERIOD
cache_period += random.uniform(0, WELL_KNOWN_DEFAULT_CACHE_PERIOD_JITTER)
return (None, cache_period)
result = parsed_body["m.server"].encode("ascii")
cache_period = _cache_period_from_headers(
response.headers, time_now=self._reactor.seconds
)
if cache_period is None:
cache_period = WELL_KNOWN_DEFAULT_CACHE_PERIOD
# add some randomness to the TTL to avoid a stampeding herd every 24 hours
# after startup
cache_period += random.uniform(0, WELL_KNOWN_DEFAULT_CACHE_PERIOD_JITTER)
else:
cache_period = min(cache_period, WELL_KNOWN_MAX_CACHE_PERIOD)
cache_period = max(cache_period, WELL_KNOWN_MIN_CACHE_PERIOD)
return (result, cache_period)
def _cache_period_from_headers(headers, time_now=time.time):
cache_controls = _parse_cache_control(headers)
if b"no-store" in cache_controls:
return 0
if b"max-age" in cache_controls:
try:
max_age = int(cache_controls[b"max-age"])
return max_age
except ValueError:
pass
expires = headers.getRawHeaders(b"expires")
if expires is not None:
try:
expires_date = stringToDatetime(expires[-1])
return expires_date - time_now()
except ValueError:
# RFC7234 says 'A cache recipient MUST interpret invalid date formats,
# especially the value "0", as representing a time in the past (i.e.,
# "already expired").
return 0
return None
def _parse_cache_control(headers):
cache_controls = {}
for hdr in headers.getRawHeaders(b"cache-control", []):
for directive in hdr.split(b","):
splits = [x.strip() for x in directive.split(b"=", 1)]
k = splits[0].lower()
v = splits[1] if len(splits) > 1 else None
cache_controls[k] = v
return cache_controls

43
tests/http/federation/test_matrix_federation_agent.py
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@ -25,17 +25,19 @@ from twisted.internet._sslverify import ClientTLSOptions, OpenSSLCertificateOpti
from twisted.internet.protocol import Factory
from twisted.protocols.tls import TLSMemoryBIOFactory
from twisted.web._newclient import ResponseNeverReceived
from twisted.web.client import Agent
from twisted.web.http import HTTPChannel
from twisted.web.http_headers import Headers
from twisted.web.iweb import IPolicyForHTTPS
from synapse.config.homeserver import HomeServerConfig
from synapse.crypto.context_factory import ClientTLSOptionsFactory
from synapse.http.federation.matrix_federation_agent import (
MatrixFederationAgent,
from synapse.http.federation.matrix_federation_agent import MatrixFederationAgent
from synapse.http.federation.srv_resolver import Server
from synapse.http.federation.well_known_resolver import (
WellKnownResolver,
_cache_period_from_headers,
)
from synapse.http.federation.srv_resolver import Server
from synapse.logging.context import LoggingContext
from synapse.util.caches.ttlcache import TTLCache
@ -79,9 +81,10 @@ class MatrixFederationAgentTests(TestCase):
self._config = config = HomeServerConfig()
config.parse_config_dict(config_dict, "", "")
self.tls_factory = ClientTLSOptionsFactory(config)
self.agent = MatrixFederationAgent(
reactor=self.reactor,
tls_client_options_factory=ClientTLSOptionsFactory(config),
tls_client_options_factory=self.tls_factory,
_srv_resolver=self.mock_resolver,
_well_known_cache=self.well_known_cache,
)
@ -928,20 +931,16 @@ class MatrixFederationAgentTests(TestCase):
self.reactor.pump((0.1,))
self.successResultOf(test_d)
@defer.inlineCallbacks
def do_get_well_known(self, serv):
try:
result = yield self.agent._get_well_known(serv)
logger.info("Result from well-known fetch: %s", result)
except Exception as e:
logger.warning("Error fetching well-known: %s", e)
raise
return result
def test_well_known_cache(self):
well_known_resolver = WellKnownResolver(
self.reactor,
Agent(self.reactor, contextFactory=self.tls_factory),
well_known_cache=self.well_known_cache,
)
self.reactor.lookups["testserv"] = "1.2.3.4"
fetch_d = self.do_get_well_known(b"testserv")
fetch_d = well_known_resolver.get_well_known(b"testserv")
# there should be an attempt to connect on port 443 for the .well-known
clients = self.reactor.tcpClients
@ -953,26 +952,26 @@ class MatrixFederationAgentTests(TestCase):
well_known_server = self._handle_well_known_connection(
client_factory,
expected_sni=b"testserv",
response_headers={b"Cache-Control": b"max-age=10"},
response_headers={b"Cache-Control": b"max-age=1000"},
content=b'{ "m.server": "target-server" }',
)
r = self.successResultOf(fetch_d)
self.assertEqual(r, b"target-server")
self.assertEqual(r.delegated_server, b"target-server")
# close the tcp connection
well_known_server.loseConnection()
# repeat the request: it should hit the cache
fetch_d = self.do_get_well_known(b"testserv")
fetch_d = well_known_resolver.get_well_known(b"testserv")
r = self.successResultOf(fetch_d)
self.assertEqual(r, b"target-server")
self.assertEqual(r.delegated_server, b"target-server")
# expire the cache
self.reactor.pump((10.0,))
self.reactor.pump((1000.0,))
# now it should connect again
fetch_d = self.do_get_well_known(b"testserv")
fetch_d = well_known_resolver.get_well_known(b"testserv")
self.assertEqual(len(clients), 1)
(host, port, client_factory, _timeout, _bindAddress) = clients.pop(0)
@ -986,7 +985,7 @@ class MatrixFederationAgentTests(TestCase):
)
r = self.successResultOf(fetch_d)
self.assertEqual(r, b"other-server")
self.assertEqual(r.delegated_server, b"other-server")
class TestCachePeriodFromHeaders(TestCase):