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# -*- coding: utf-8 -*-
# Copyright 2014 matrix.org
#
# 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.
from twisted.internet.endpoints import SSL4ClientEndpoint, TCP4ClientEndpoint
from twisted.internet import defer
from twisted.internet.error import ConnectError
from twisted.names import client, dns
from twisted.names.error import DNSNameError
import collections
import logging
import random
logger = logging.getLogger(__name__)
def matrix_endpoint(reactor, destination, ssl_context_factory=None,
timeout=None):
"""Construct an endpoint for the given matrix destination.
Args:
reactor: Twisted reactor.
destination (bytes): The name of the server to connect to.
ssl_context_factory (twisted.internet.ssl.ContextFactory): Factory
which generates SSL contexts to use for TLS.
timeout (int): connection timeout in seconds
"""
domain_port = destination.split(":")
domain = domain_port[0]
port = int(domain_port[1]) if domain_port[1:] else None
endpoint_kw_args = {}
if timeout is not None:
endpoint_kw_args.update(timeout=timeout)
if ssl_context_factory is None:
transport_endpoint = TCP4ClientEndpoint
default_port = 8080
else:
transport_endpoint = SSL4ClientEndpoint
endpoint_kw_args.update(ssl_context_factory=ssl_context_factory)
default_port = 443
if port is None:
return SRVClientEndpoint(
reactor, "matrix", domain, protocol="tcp",
default_port=default_port, endpoint=transport_endpoint,
endpoint_kw_args=endpoint_kw_args
)
else:
return transport_endpoint(reactor, domain, port, **endpoint_kw_args)
class SRVClientEndpoint(object):
"""An endpoint which looks up SRV records for a service.
Cycles through the list of servers starting with each call to connect
picking the next server.
Implements twisted.internet.interfaces.IStreamClientEndpoint.
"""
_Server = collections.namedtuple(
"_Server", "priority weight host port"
)
def __init__(self, reactor, service, domain, protocol="tcp",
default_port=None, endpoint=TCP4ClientEndpoint,
endpoint_kw_args={}):
self.reactor = reactor
self.service_name = "_%s._%s.%s" % (service, protocol, domain)
if default_port is not None:
self.default_server = self._Server(
host=domain,
port=default_port,
priority=0,
weight=0
)
else:
self.default_server = None
self.endpoint = endpoint
self.endpoint_kw_args = endpoint_kw_args
self.servers = None
self.used_servers = None
@defer.inlineCallbacks
def fetch_servers(self):
try:
answers, auth, add = yield client.lookupService(self.service_name)
except DNSNameError:
answers = []
if (len(answers) == 1
and answers[0].type == dns.SRV
and answers[0].payload
and answers[0].payload.target == dns.Name('.')):
raise ConnectError("Service %s unavailable", self.service_name)
self.servers = []
self.used_servers = []
for answer in answers:
if answer.type != dns.SRV or not answer.payload:
continue
payload = answer.payload
self.servers.append(self._Server(
host=str(payload.target),
port=int(payload.port),
priority=int(payload.priority),
weight=int(payload.weight)
))
self.servers.sort()
def pick_server(self):
if not self.servers:
if self.used_servers:
self.servers = self.used_servers
self.used_servers = []
self.servers.sort()
elif self.default_server:
return self.default_server
else:
raise ConnectError(
"Not server available for %s", self.service_name
)
min_priority = self.servers[0].priority
weight_indexes = list(
(index, server.weight + 1)
for index, server in enumerate(self.servers)
if server.priority == min_priority
)
total_weight = sum(weight for index, weight in weight_indexes)
target_weight = random.randint(0, total_weight)
for index, weight in weight_indexes:
target_weight -= weight
if target_weight <= 0:
server = self.servers[index]
del self.servers[index]
self.used_servers.append(server)
return server
@defer.inlineCallbacks
def connect(self, protocolFactory):
if self.servers is None:
yield self.fetch_servers()
server = self.pick_server()
logger.info("Connecting to %s:%s", server.host, server.port)
endpoint = self.endpoint(
self.reactor, server.host, server.port, **self.endpoint_kw_args
)
connection = yield endpoint.connect(protocolFactory)
defer.returnValue(connection)
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