MatrixFederationAgent

Pull the magic that is currently in matrix_federation_endpoint and friends into
an agent-like thing
This commit is contained in:
Richard van der Hoff 2019-01-21 23:27:57 +00:00
parent 6bfa735a69
commit 44be7513bf
2 changed files with 147 additions and 0 deletions

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@ -0,0 +1,114 @@
# -*- coding: utf-8 -*-
# Copyright 2019 New Vector Ltd
#
# 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 logging
from zope.interface import implementer
from twisted.internet import defer
from twisted.internet.endpoints import HostnameEndpoint, wrapClientTLS
from twisted.web.client import URI, Agent, HTTPConnectionPool
from twisted.web.iweb import IAgent
from synapse.http.endpoint import parse_server_name
from synapse.http.federation.srv_resolver import pick_server_from_list, resolve_service
from synapse.util.logcontext import make_deferred_yieldable
logger = logging.getLogger(__name__)
@implementer(IAgent)
class MatrixFederationAgent(object):
"""An Agent-like thing which provides a `request` method which will look up a matrix
server and send an HTTP request to it.
Doesn't implement any retries. (Those are done in MatrixFederationHttpClient.)
Args:
reactor (IReactor): twisted reactor to use for underlying requests
tls_client_options_factory (ClientTLSOptionsFactory|None):
factory to use for fetching client tls options, or none to disable TLS.
"""
def __init__(self, reactor, tls_client_options_factory):
self._reactor = reactor
self._tls_client_options_factory = tls_client_options_factory
self._pool = HTTPConnectionPool(reactor)
self._pool.retryAutomatically = False
self._pool.maxPersistentPerHost = 5
self._pool.cachedConnectionTimeout = 2 * 60
@defer.inlineCallbacks
def request(self, method, uri, headers=None, bodyProducer=None):
"""
Args:
method (bytes): HTTP method: GET/POST/etc
uri (bytes): Absolute URI to be retrieved
headers (twisted.web.http_headers.Headers|None):
HTTP headers to send with the request, or None to
send no extra headers.
bodyProducer (twisted.web.iweb.IBodyProducer|None):
An object which can generate bytes to make up the
body of this request (for example, the properly encoded contents of
a file for a file upload). Or None if the request is to have
no body.
Returns:
Deferred[twisted.web.iweb.IResponse]:
fires when the header of the response has been received (regardless of the
response status code). Fails if there is any problem which prevents that
response from being received (including problems that prevent the request
from being sent).
"""
parsed_uri = URI.fromBytes(uri)
server_name_bytes = parsed_uri.netloc
host, port = parse_server_name(server_name_bytes.decode("ascii"))
# XXX disabling TLS is really only supported here for the benefit of the
# unit tests. We should make the UTs cope with TLS rather than having to make
# the code support the unit tests.
if self._tls_client_options_factory is None:
tls_options = None
else:
tls_options = self._tls_client_options_factory.get_options(host)
if port is not None:
target = (host, port)
else:
server_list = yield resolve_service(server_name_bytes)
if not server_list:
target = (host, 8448)
logger.debug("No SRV record for %s, using %s", host, target)
else:
target = pick_server_from_list(server_list)
class EndpointFactory(object):
@staticmethod
def endpointForURI(_uri):
logger.info("Connecting to %s:%s", target[0], target[1])
ep = HostnameEndpoint(self._reactor, host=target[0], port=target[1])
if tls_options is not None:
ep = wrapClientTLS(tls_options, ep)
return ep
agent = Agent.usingEndpointFactory(self._reactor, EndpointFactory(), self._pool)
res = yield make_deferred_yieldable(
agent.request(method, uri, headers, bodyProducer)
)
defer.returnValue(res)

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@ -15,6 +15,7 @@
# limitations under the License.
import logging
import random
import time
import attr
@ -51,6 +52,38 @@ class Server(object):
expires = attr.ib(default=0)
def pick_server_from_list(server_list):
"""Randomly choose a server from the server list
Args:
server_list (list[Server]): list of candidate servers
Returns:
Tuple[bytes, int]: (host, port) pair for the chosen server
"""
if not server_list:
raise RuntimeError("pick_server_from_list called with empty list")
# TODO: currently we only use the lowest-priority servers. We should maintain a
# cache of servers known to be "down" and filter them out
min_priority = min(s.priority for s in server_list)
eligible_servers = list(s for s in server_list if s.priority == min_priority)
total_weight = sum(s.weight for s in eligible_servers)
target_weight = random.randint(0, total_weight)
for s in eligible_servers:
target_weight -= s.weight
if target_weight <= 0:
return s.host, s.port
# this should be impossible.
raise RuntimeError(
"pick_server_from_list got to end of eligible server list.",
)
@defer.inlineCallbacks
def resolve_service(service_name, dns_client=client, cache=SERVER_CACHE, clock=time):
"""Look up a SRV record, with caching