MatrixSynapse/synapse/http/matrixfederationclient.py

991 lines
34 KiB
Python

# -*- coding: utf-8 -*-
# Copyright 2014-2016 OpenMarket Ltd
# Copyright 2018 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 cgi
import logging
import random
import sys
from io import BytesIO
from six import PY3, raise_from, string_types
from six.moves import urllib
import attr
import treq
from canonicaljson import encode_canonical_json
from prometheus_client import Counter
from signedjson.sign import sign_json
from zope.interface import implementer
from twisted.internet import defer, protocol
from twisted.internet.error import DNSLookupError
from twisted.internet.interfaces import IReactorPluggableNameResolver
from twisted.internet.task import _EPSILON, Cooperator
from twisted.web._newclient import ResponseDone
from twisted.web.http_headers import Headers
import synapse.logging.opentracing as opentracing
import synapse.metrics
import synapse.util.retryutils
from synapse.api.errors import (
Codes,
FederationDeniedError,
HttpResponseException,
RequestSendFailed,
SynapseError,
)
from synapse.http import QuieterFileBodyProducer
from synapse.http.client import BlacklistingAgentWrapper, IPBlacklistingResolver
from synapse.http.federation.matrix_federation_agent import MatrixFederationAgent
from synapse.logging.context import make_deferred_yieldable
from synapse.util.async_helpers import timeout_deferred
from synapse.util.metrics import Measure
logger = logging.getLogger(__name__)
outgoing_requests_counter = Counter(
"synapse_http_matrixfederationclient_requests", "", ["method"]
)
incoming_responses_counter = Counter(
"synapse_http_matrixfederationclient_responses", "", ["method", "code"]
)
MAX_LONG_RETRIES = 10
MAX_SHORT_RETRIES = 3
if PY3:
MAXINT = sys.maxsize
else:
MAXINT = sys.maxint
_next_id = 1
@attr.s
class MatrixFederationRequest(object):
method = attr.ib()
"""HTTP method
:type: str
"""
path = attr.ib()
"""HTTP path
:type: str
"""
destination = attr.ib()
"""The remote server to send the HTTP request to.
:type: str"""
json = attr.ib(default=None)
"""JSON to send in the body.
:type: dict|None
"""
json_callback = attr.ib(default=None)
"""A callback to generate the JSON.
:type: func|None
"""
query = attr.ib(default=None)
"""Query arguments.
:type: dict|None
"""
txn_id = attr.ib(default=None)
"""Unique ID for this request (for logging)
:type: str|None
"""
def __attrs_post_init__(self):
global _next_id
self.txn_id = "%s-O-%s" % (self.method, _next_id)
_next_id = (_next_id + 1) % (MAXINT - 1)
def get_json(self):
if self.json_callback:
return self.json_callback()
return self.json
@defer.inlineCallbacks
def _handle_json_response(reactor, timeout_sec, request, response):
"""
Reads the JSON body of a response, with a timeout
Args:
reactor (IReactor): twisted reactor, for the timeout
timeout_sec (float): number of seconds to wait for response to complete
request (MatrixFederationRequest): the request that triggered the response
response (IResponse): response to the request
Returns:
dict: parsed JSON response
"""
try:
check_content_type_is_json(response.headers)
d = treq.json_content(response)
d = timeout_deferred(d, timeout=timeout_sec, reactor=reactor)
body = yield make_deferred_yieldable(d)
except Exception as e:
logger.warn(
"{%s} [%s] Error reading response: %s",
request.txn_id,
request.destination,
e,
)
raise
logger.info(
"{%s} [%s] Completed: %d %s",
request.txn_id,
request.destination,
response.code,
response.phrase.decode("ascii", errors="replace"),
)
return body
class MatrixFederationHttpClient(object):
"""HTTP client used to talk to other homeservers over the federation
protocol. Send client certificates and signs requests.
Attributes:
agent (twisted.web.client.Agent): The twisted Agent used to send the
requests.
"""
def __init__(self, hs, tls_client_options_factory):
self.hs = hs
self.signing_key = hs.config.signing_key[0]
self.server_name = hs.hostname
real_reactor = hs.get_reactor()
# We need to use a DNS resolver which filters out blacklisted IP
# addresses, to prevent DNS rebinding.
nameResolver = IPBlacklistingResolver(
real_reactor, None, hs.config.federation_ip_range_blacklist
)
@implementer(IReactorPluggableNameResolver)
class Reactor(object):
def __getattr__(_self, attr):
if attr == "nameResolver":
return nameResolver
else:
return getattr(real_reactor, attr)
self.reactor = Reactor()
self.agent = MatrixFederationAgent(self.reactor, tls_client_options_factory)
# Use a BlacklistingAgentWrapper to prevent circumventing the IP
# blacklist via IP literals in server names
self.agent = BlacklistingAgentWrapper(
self.agent,
self.reactor,
ip_blacklist=hs.config.federation_ip_range_blacklist,
)
self.clock = hs.get_clock()
self._store = hs.get_datastore()
self.version_string_bytes = hs.version_string.encode("ascii")
self.default_timeout = 60
def schedule(x):
self.reactor.callLater(_EPSILON, x)
self._cooperator = Cooperator(scheduler=schedule)
@defer.inlineCallbacks
def _send_request_with_optional_trailing_slash(
self, request, try_trailing_slash_on_400=False, **send_request_args
):
"""Wrapper for _send_request which can optionally retry the request
upon receiving a combination of a 400 HTTP response code and a
'M_UNRECOGNIZED' errcode. This is a workaround for Synapse <= v0.99.3
due to #3622.
Args:
request (MatrixFederationRequest): details of request to be sent
try_trailing_slash_on_400 (bool): Whether on receiving a 400
'M_UNRECOGNIZED' from the server to retry the request with a
trailing slash appended to the request path.
send_request_args (Dict): A dictionary of arguments to pass to
`_send_request()`.
Raises:
HttpResponseException: If we get an HTTP response code >= 300
(except 429).
Returns:
Deferred[Dict]: Parsed JSON response body.
"""
try:
response = yield self._send_request(request, **send_request_args)
except HttpResponseException as e:
# Received an HTTP error > 300. Check if it meets the requirements
# to retry with a trailing slash
if not try_trailing_slash_on_400:
raise
if e.code != 400 or e.to_synapse_error().errcode != "M_UNRECOGNIZED":
raise
# Retry with a trailing slash if we received a 400 with
# 'M_UNRECOGNIZED' which some endpoints can return when omitting a
# trailing slash on Synapse <= v0.99.3.
logger.info("Retrying request with trailing slash")
request.path += "/"
response = yield self._send_request(request, **send_request_args)
return response
@defer.inlineCallbacks
def _send_request(
self,
request,
retry_on_dns_fail=True,
timeout=None,
long_retries=False,
ignore_backoff=False,
backoff_on_404=False,
):
"""
Sends a request to the given server.
Args:
request (MatrixFederationRequest): details of request to be sent
timeout (int|None): number of milliseconds to wait for the response headers
(including connecting to the server), *for each attempt*.
60s by default.
long_retries (bool): whether to use the long retry algorithm.
The regular retry algorithm makes 4 attempts, with intervals
[0.5s, 1s, 2s].
The long retry algorithm makes 11 attempts, with intervals
[4s, 16s, 60s, 60s, ...]
Both algorithms add -20%/+40% jitter to the retry intervals.
Note that the above intervals are *in addition* to the time spent
waiting for the request to complete (up to `timeout` ms).
NB: the long retry algorithm takes over 20 minutes to complete, with
a default timeout of 60s!
ignore_backoff (bool): true to ignore the historical backoff data
and try the request anyway.
backoff_on_404 (bool): Back off if we get a 404
Returns:
Deferred[twisted.web.client.Response]: resolves with the HTTP
response object on success.
Raises:
HttpResponseException: If we get an HTTP response code >= 300
(except 429).
NotRetryingDestination: If we are not yet ready to retry this
server.
FederationDeniedError: If this destination is not on our
federation whitelist
RequestSendFailed: If there were problems connecting to the
remote, due to e.g. DNS failures, connection timeouts etc.
"""
if timeout:
_sec_timeout = timeout / 1000
else:
_sec_timeout = self.default_timeout
if (
self.hs.config.federation_domain_whitelist is not None
and request.destination not in self.hs.config.federation_domain_whitelist
):
raise FederationDeniedError(request.destination)
limiter = yield synapse.util.retryutils.get_retry_limiter(
request.destination,
self.clock,
self._store,
backoff_on_404=backoff_on_404,
ignore_backoff=ignore_backoff,
)
method_bytes = request.method.encode("ascii")
destination_bytes = request.destination.encode("ascii")
path_bytes = request.path.encode("ascii")
if request.query:
query_bytes = encode_query_args(request.query)
else:
query_bytes = b""
# Retreive current span
scope = opentracing.start_active_span(
"outgoing-federation-request",
tags={
opentracing.tags.SPAN_KIND: opentracing.tags.SPAN_KIND_RPC_CLIENT,
opentracing.tags.PEER_ADDRESS: request.destination,
opentracing.tags.HTTP_METHOD: request.method,
opentracing.tags.HTTP_URL: request.path,
},
finish_on_close=True,
)
# Inject the span into the headers
headers_dict = {}
opentracing.inject_active_span_byte_dict(headers_dict, request.destination)
headers_dict[b"User-Agent"] = [self.version_string_bytes]
with limiter, scope:
# XXX: Would be much nicer to retry only at the transaction-layer
# (once we have reliable transactions in place)
if long_retries:
retries_left = MAX_LONG_RETRIES
else:
retries_left = MAX_SHORT_RETRIES
url_bytes = urllib.parse.urlunparse(
(b"matrix", destination_bytes, path_bytes, None, query_bytes, b"")
)
url_str = url_bytes.decode("ascii")
url_to_sign_bytes = urllib.parse.urlunparse(
(b"", b"", path_bytes, None, query_bytes, b"")
)
while True:
try:
json = request.get_json()
if json:
headers_dict[b"Content-Type"] = [b"application/json"]
auth_headers = self.build_auth_headers(
destination_bytes, method_bytes, url_to_sign_bytes, json
)
data = encode_canonical_json(json)
producer = QuieterFileBodyProducer(
BytesIO(data), cooperator=self._cooperator
)
else:
producer = None
auth_headers = self.build_auth_headers(
destination_bytes, method_bytes, url_to_sign_bytes
)
headers_dict[b"Authorization"] = auth_headers
logger.info(
"{%s} [%s] Sending request: %s %s; timeout %fs",
request.txn_id,
request.destination,
request.method,
url_str,
_sec_timeout,
)
try:
with Measure(self.clock, "outbound_request"):
# we don't want all the fancy cookie and redirect handling
# that treq.request gives: just use the raw Agent.
request_deferred = self.agent.request(
method_bytes,
url_bytes,
headers=Headers(headers_dict),
bodyProducer=producer,
)
request_deferred = timeout_deferred(
request_deferred,
timeout=_sec_timeout,
reactor=self.reactor,
)
response = yield request_deferred
except DNSLookupError as e:
raise_from(RequestSendFailed(e, can_retry=retry_on_dns_fail), e)
except Exception as e:
logger.info("Failed to send request: %s", e)
raise_from(RequestSendFailed(e, can_retry=True), e)
logger.info(
"{%s} [%s] Got response headers: %d %s",
request.txn_id,
request.destination,
response.code,
response.phrase.decode("ascii", errors="replace"),
)
opentracing.set_tag(
opentracing.tags.HTTP_STATUS_CODE, response.code
)
if 200 <= response.code < 300:
pass
else:
# :'(
# Update transactions table?
d = treq.content(response)
d = timeout_deferred(
d, timeout=_sec_timeout, reactor=self.reactor
)
try:
body = yield make_deferred_yieldable(d)
except Exception as e:
# Eh, we're already going to raise an exception so lets
# ignore if this fails.
logger.warn(
"{%s} [%s] Failed to get error response: %s %s: %s",
request.txn_id,
request.destination,
request.method,
url_str,
_flatten_response_never_received(e),
)
body = None
e = HttpResponseException(response.code, response.phrase, body)
# Retry if the error is a 429 (Too Many Requests),
# otherwise just raise a standard HttpResponseException
if response.code == 429:
raise_from(RequestSendFailed(e, can_retry=True), e)
else:
raise e
break
except RequestSendFailed as e:
logger.warn(
"{%s} [%s] Request failed: %s %s: %s",
request.txn_id,
request.destination,
request.method,
url_str,
_flatten_response_never_received(e.inner_exception),
)
if not e.can_retry:
raise
if retries_left and not timeout:
if long_retries:
delay = 4 ** (MAX_LONG_RETRIES + 1 - retries_left)
delay = min(delay, 60)
delay *= random.uniform(0.8, 1.4)
else:
delay = 0.5 * 2 ** (MAX_SHORT_RETRIES - retries_left)
delay = min(delay, 2)
delay *= random.uniform(0.8, 1.4)
logger.debug(
"{%s} [%s] Waiting %ss before re-sending...",
request.txn_id,
request.destination,
delay,
)
yield self.clock.sleep(delay)
retries_left -= 1
else:
raise
except Exception as e:
logger.warn(
"{%s} [%s] Request failed: %s %s: %s",
request.txn_id,
request.destination,
request.method,
url_str,
_flatten_response_never_received(e),
)
raise
return response
def build_auth_headers(
self, destination, method, url_bytes, content=None, destination_is=None
):
"""
Builds the Authorization headers for a federation request
Args:
destination (bytes|None): The desination home server of the request.
May be None if the destination is an identity server, in which case
destination_is must be non-None.
method (bytes): The HTTP method of the request
url_bytes (bytes): The URI path of the request
content (object): The body of the request
destination_is (bytes): As 'destination', but if the destination is an
identity server
Returns:
list[bytes]: a list of headers to be added as "Authorization:" headers
"""
request = {"method": method, "uri": url_bytes, "origin": self.server_name}
if destination is not None:
request["destination"] = destination
if destination_is is not None:
request["destination_is"] = destination_is
if content is not None:
request["content"] = content
request = sign_json(request, self.server_name, self.signing_key)
auth_headers = []
for key, sig in request["signatures"][self.server_name].items():
auth_headers.append(
(
'X-Matrix origin=%s,key="%s",sig="%s"'
% (self.server_name, key, sig)
).encode("ascii")
)
return auth_headers
@defer.inlineCallbacks
def put_json(
self,
destination,
path,
args={},
data={},
json_data_callback=None,
long_retries=False,
timeout=None,
ignore_backoff=False,
backoff_on_404=False,
try_trailing_slash_on_400=False,
):
""" Sends the specifed json data using PUT
Args:
destination (str): The remote server to send the HTTP request
to.
path (str): The HTTP path.
args (dict): query params
data (dict): A dict containing the data that will be used as
the request body. This will be encoded as JSON.
json_data_callback (callable): A callable returning the dict to
use as the request body.
long_retries (bool): whether to use the long retry algorithm. See
docs on _send_request for details.
timeout (int|None): number of milliseconds to wait for the response headers
(including connecting to the server), *for each attempt*.
self._default_timeout (60s) by default.
ignore_backoff (bool): true to ignore the historical backoff data
and try the request anyway.
backoff_on_404 (bool): True if we should count a 404 response as
a failure of the server (and should therefore back off future
requests).
try_trailing_slash_on_400 (bool): True if on a 400 M_UNRECOGNIZED
response we should try appending a trailing slash to the end
of the request. Workaround for #3622 in Synapse <= v0.99.3. This
will be attempted before backing off if backing off has been
enabled.
Returns:
Deferred[dict|list]: Succeeds when we get a 2xx HTTP response. The
result will be the decoded JSON body.
Raises:
HttpResponseException: If we get an HTTP response code >= 300
(except 429).
NotRetryingDestination: If we are not yet ready to retry this
server.
FederationDeniedError: If this destination is not on our
federation whitelist
RequestSendFailed: If there were problems connecting to the
remote, due to e.g. DNS failures, connection timeouts etc.
"""
request = MatrixFederationRequest(
method="PUT",
destination=destination,
path=path,
query=args,
json_callback=json_data_callback,
json=data,
)
response = yield self._send_request_with_optional_trailing_slash(
request,
try_trailing_slash_on_400,
backoff_on_404=backoff_on_404,
ignore_backoff=ignore_backoff,
long_retries=long_retries,
timeout=timeout,
)
body = yield _handle_json_response(
self.reactor, self.default_timeout, request, response
)
return body
@defer.inlineCallbacks
def post_json(
self,
destination,
path,
data={},
long_retries=False,
timeout=None,
ignore_backoff=False,
args={},
):
""" Sends the specifed json data using POST
Args:
destination (str): The remote server to send the HTTP request
to.
path (str): The HTTP path.
data (dict): A dict containing the data that will be used as
the request body. This will be encoded as JSON.
long_retries (bool): whether to use the long retry algorithm. See
docs on _send_request for details.
timeout (int|None): number of milliseconds to wait for the response headers
(including connecting to the server), *for each attempt*.
self._default_timeout (60s) by default.
ignore_backoff (bool): true to ignore the historical backoff data and
try the request anyway.
args (dict): query params
Returns:
Deferred[dict|list]: Succeeds when we get a 2xx HTTP response. The
result will be the decoded JSON body.
Raises:
HttpResponseException: If we get an HTTP response code >= 300
(except 429).
NotRetryingDestination: If we are not yet ready to retry this
server.
FederationDeniedError: If this destination is not on our
federation whitelist
RequestSendFailed: If there were problems connecting to the
remote, due to e.g. DNS failures, connection timeouts etc.
"""
request = MatrixFederationRequest(
method="POST", destination=destination, path=path, query=args, json=data
)
response = yield self._send_request(
request,
long_retries=long_retries,
timeout=timeout,
ignore_backoff=ignore_backoff,
)
if timeout:
_sec_timeout = timeout / 1000
else:
_sec_timeout = self.default_timeout
body = yield _handle_json_response(
self.reactor, _sec_timeout, request, response
)
return body
@defer.inlineCallbacks
def get_json(
self,
destination,
path,
args=None,
retry_on_dns_fail=True,
timeout=None,
ignore_backoff=False,
try_trailing_slash_on_400=False,
):
""" GETs some json from the given host homeserver and path
Args:
destination (str): The remote server to send the HTTP request
to.
path (str): The HTTP path.
args (dict|None): A dictionary used to create query strings, defaults to
None.
timeout (int|None): number of milliseconds to wait for the response headers
(including connecting to the server), *for each attempt*.
self._default_timeout (60s) by default.
ignore_backoff (bool): true to ignore the historical backoff data
and try the request anyway.
try_trailing_slash_on_400 (bool): True if on a 400 M_UNRECOGNIZED
response we should try appending a trailing slash to the end of
the request. Workaround for #3622 in Synapse <= v0.99.3.
Returns:
Deferred[dict|list]: Succeeds when we get a 2xx HTTP response. The
result will be the decoded JSON body.
Raises:
HttpResponseException: If we get an HTTP response code >= 300
(except 429).
NotRetryingDestination: If we are not yet ready to retry this
server.
FederationDeniedError: If this destination is not on our
federation whitelist
RequestSendFailed: If there were problems connecting to the
remote, due to e.g. DNS failures, connection timeouts etc.
"""
request = MatrixFederationRequest(
method="GET", destination=destination, path=path, query=args
)
response = yield self._send_request_with_optional_trailing_slash(
request,
try_trailing_slash_on_400,
backoff_on_404=False,
ignore_backoff=ignore_backoff,
retry_on_dns_fail=retry_on_dns_fail,
timeout=timeout,
)
body = yield _handle_json_response(
self.reactor, self.default_timeout, request, response
)
return body
@defer.inlineCallbacks
def delete_json(
self,
destination,
path,
long_retries=False,
timeout=None,
ignore_backoff=False,
args={},
):
"""Send a DELETE request to the remote expecting some json response
Args:
destination (str): The remote server to send the HTTP request
to.
path (str): The HTTP path.
long_retries (bool): whether to use the long retry algorithm. See
docs on _send_request for details.
timeout (int|None): number of milliseconds to wait for the response headers
(including connecting to the server), *for each attempt*.
self._default_timeout (60s) by default.
ignore_backoff (bool): true to ignore the historical backoff data and
try the request anyway.
args (dict): query params
Returns:
Deferred[dict|list]: Succeeds when we get a 2xx HTTP response. The
result will be the decoded JSON body.
Raises:
HttpResponseException: If we get an HTTP response code >= 300
(except 429).
NotRetryingDestination: If we are not yet ready to retry this
server.
FederationDeniedError: If this destination is not on our
federation whitelist
RequestSendFailed: If there were problems connecting to the
remote, due to e.g. DNS failures, connection timeouts etc.
"""
request = MatrixFederationRequest(
method="DELETE", destination=destination, path=path, query=args
)
response = yield self._send_request(
request,
long_retries=long_retries,
timeout=timeout,
ignore_backoff=ignore_backoff,
)
body = yield _handle_json_response(
self.reactor, self.default_timeout, request, response
)
return body
@defer.inlineCallbacks
def get_file(
self,
destination,
path,
output_stream,
args={},
retry_on_dns_fail=True,
max_size=None,
ignore_backoff=False,
):
"""GETs a file from a given homeserver
Args:
destination (str): The remote server to send the HTTP request to.
path (str): The HTTP path to GET.
output_stream (file): File to write the response body to.
args (dict): Optional dictionary used to create the query string.
ignore_backoff (bool): true to ignore the historical backoff data
and try the request anyway.
Returns:
Deferred[tuple[int, dict]]: Resolves with an (int,dict) tuple of
the file length and a dict of the response headers.
Raises:
HttpResponseException: If we get an HTTP response code >= 300
(except 429).
NotRetryingDestination: If we are not yet ready to retry this
server.
FederationDeniedError: If this destination is not on our
federation whitelist
RequestSendFailed: If there were problems connecting to the
remote, due to e.g. DNS failures, connection timeouts etc.
"""
request = MatrixFederationRequest(
method="GET", destination=destination, path=path, query=args
)
response = yield self._send_request(
request, retry_on_dns_fail=retry_on_dns_fail, ignore_backoff=ignore_backoff
)
headers = dict(response.headers.getAllRawHeaders())
try:
d = _readBodyToFile(response, output_stream, max_size)
d.addTimeout(self.default_timeout, self.reactor)
length = yield make_deferred_yieldable(d)
except Exception as e:
logger.warn(
"{%s} [%s] Error reading response: %s",
request.txn_id,
request.destination,
e,
)
raise
logger.info(
"{%s} [%s] Completed: %d %s [%d bytes]",
request.txn_id,
request.destination,
response.code,
response.phrase.decode("ascii", errors="replace"),
length,
)
return (length, headers)
class _ReadBodyToFileProtocol(protocol.Protocol):
def __init__(self, stream, deferred, max_size):
self.stream = stream
self.deferred = deferred
self.length = 0
self.max_size = max_size
def dataReceived(self, data):
self.stream.write(data)
self.length += len(data)
if self.max_size is not None and self.length >= self.max_size:
self.deferred.errback(
SynapseError(
502,
"Requested file is too large > %r bytes" % (self.max_size,),
Codes.TOO_LARGE,
)
)
self.deferred = defer.Deferred()
self.transport.loseConnection()
def connectionLost(self, reason):
if reason.check(ResponseDone):
self.deferred.callback(self.length)
else:
self.deferred.errback(reason)
def _readBodyToFile(response, stream, max_size):
d = defer.Deferred()
response.deliverBody(_ReadBodyToFileProtocol(stream, d, max_size))
return d
def _flatten_response_never_received(e):
if hasattr(e, "reasons"):
reasons = ", ".join(
_flatten_response_never_received(f.value) for f in e.reasons
)
return "%s:[%s]" % (type(e).__name__, reasons)
else:
return repr(e)
def check_content_type_is_json(headers):
"""
Check that a set of HTTP headers have a Content-Type header, and that it
is application/json.
Args:
headers (twisted.web.http_headers.Headers): headers to check
Raises:
RequestSendFailed: if the Content-Type header is missing or isn't JSON
"""
c_type = headers.getRawHeaders(b"Content-Type")
if c_type is None:
raise RequestSendFailed(RuntimeError("No Content-Type header"), can_retry=False)
c_type = c_type[0].decode("ascii") # only the first header
val, options = cgi.parse_header(c_type)
if val != "application/json":
raise RequestSendFailed(
RuntimeError("Content-Type not application/json: was '%s'" % c_type),
can_retry=False,
)
def encode_query_args(args):
if args is None:
return b""
encoded_args = {}
for k, vs in args.items():
if isinstance(vs, string_types):
vs = [vs]
encoded_args[k] = [v.encode("UTF-8") for v in vs]
query_bytes = urllib.parse.urlencode(encoded_args, True)
return query_bytes.encode("utf8")