mirror of
https://git.anonymousland.org/anonymousland/synapse-product.git
synced 2024-12-11 10:14:22 -05:00
b28a7ed503
If a HTTP handler throws an exception while processing a request we automatically write a JSON error response. If the handler had already started writing a response twisted throws an exception. We should check for this case and simple abort the connection if there was an error after the response had started being written.
508 lines
17 KiB
Python
508 lines
17 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright 2014-2016 OpenMarket Ltd
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# Copyright 2018 New Vector Ltd
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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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import cgi
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import collections
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import logging
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from six import PY3
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from six.moves import http_client, urllib
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from canonicaljson import encode_canonical_json, encode_pretty_printed_json, json
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from twisted.internet import defer
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from twisted.python import failure
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from twisted.web import resource
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from twisted.web.server import NOT_DONE_YET
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from twisted.web.static import NoRangeStaticProducer
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from twisted.web.util import redirectTo
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import synapse.events
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import synapse.metrics
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from synapse.api.errors import (
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CodeMessageException,
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Codes,
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SynapseError,
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UnrecognizedRequestError,
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)
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from synapse.util.caches import intern_dict
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from synapse.util.logcontext import preserve_fn
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if PY3:
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from io import BytesIO
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else:
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from cStringIO import StringIO as BytesIO
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logger = logging.getLogger(__name__)
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HTML_ERROR_TEMPLATE = """<!DOCTYPE html>
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<html lang=en>
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<head>
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<meta charset="utf-8">
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<title>Error {code}</title>
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</head>
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<body>
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<p>{msg}</p>
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</body>
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</html>
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"""
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def wrap_json_request_handler(h):
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"""Wraps a request handler method with exception handling.
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Also does the wrapping with request.processing as per wrap_async_request_handler.
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The handler method must have a signature of "handle_foo(self, request)",
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where "request" must be a SynapseRequest.
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The handler must return a deferred. If the deferred succeeds we assume that
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a response has been sent. If the deferred fails with a SynapseError we use
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it to send a JSON response with the appropriate HTTP reponse code. If the
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deferred fails with any other type of error we send a 500 reponse.
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"""
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@defer.inlineCallbacks
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def wrapped_request_handler(self, request):
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try:
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yield h(self, request)
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except SynapseError as e:
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code = e.code
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logger.info(
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"%s SynapseError: %s - %s", request, code, e.msg
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)
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# Only respond with an error response if we haven't already started
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# writing, otherwise lets just kill the connection
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if request.startedWriting:
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if request.transport:
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try:
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request.transport.abortConnection()
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except Exception:
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# abortConnection throws if the connection is already closed
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pass
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else:
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respond_with_json(
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request, code, e.error_dict(), send_cors=True,
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pretty_print=_request_user_agent_is_curl(request),
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)
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except Exception:
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# failure.Failure() fishes the original Failure out
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# of our stack, and thus gives us a sensible stack
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# trace.
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f = failure.Failure()
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logger.error(
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"Failed handle request via %r: %r: %s",
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h,
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request,
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f.getTraceback().rstrip(),
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)
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# Only respond with an error response if we haven't already started
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# writing, otherwise lets just kill the connection
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if request.startedWriting:
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if request.transport:
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try:
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request.transport.abortConnection()
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except Exception:
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# abortConnection throws if the connection is already closed
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pass
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else:
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respond_with_json(
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request,
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500,
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{
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"error": "Internal server error",
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"errcode": Codes.UNKNOWN,
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},
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send_cors=True,
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pretty_print=_request_user_agent_is_curl(request),
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)
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return wrap_async_request_handler(wrapped_request_handler)
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def wrap_html_request_handler(h):
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"""Wraps a request handler method with exception handling.
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Also does the wrapping with request.processing as per wrap_async_request_handler.
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The handler method must have a signature of "handle_foo(self, request)",
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where "request" must be a SynapseRequest.
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"""
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def wrapped_request_handler(self, request):
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d = defer.maybeDeferred(h, self, request)
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d.addErrback(_return_html_error, request)
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return d
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return wrap_async_request_handler(wrapped_request_handler)
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def _return_html_error(f, request):
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"""Sends an HTML error page corresponding to the given failure
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Args:
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f (twisted.python.failure.Failure):
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request (twisted.web.iweb.IRequest):
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"""
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if f.check(CodeMessageException):
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cme = f.value
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code = cme.code
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msg = cme.msg
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if isinstance(cme, SynapseError):
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logger.info(
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"%s SynapseError: %s - %s", request, code, msg
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)
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else:
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logger.error(
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"Failed handle request %r: %s",
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request,
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f.getTraceback().rstrip(),
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)
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else:
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code = http_client.INTERNAL_SERVER_ERROR
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msg = "Internal server error"
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logger.error(
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"Failed handle request %r: %s",
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request,
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f.getTraceback().rstrip(),
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)
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body = HTML_ERROR_TEMPLATE.format(
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code=code, msg=cgi.escape(msg),
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).encode("utf-8")
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request.setResponseCode(code)
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request.setHeader(b"Content-Type", b"text/html; charset=utf-8")
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request.setHeader(b"Content-Length", b"%i" % (len(body),))
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request.write(body)
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finish_request(request)
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def wrap_async_request_handler(h):
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"""Wraps an async request handler so that it calls request.processing.
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This helps ensure that work done by the request handler after the request is completed
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is correctly recorded against the request metrics/logs.
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The handler method must have a signature of "handle_foo(self, request)",
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where "request" must be a SynapseRequest.
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The handler may return a deferred, in which case the completion of the request isn't
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logged until the deferred completes.
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"""
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@defer.inlineCallbacks
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def wrapped_async_request_handler(self, request):
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with request.processing():
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yield h(self, request)
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# we need to preserve_fn here, because the synchronous render method won't yield for
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# us (obviously)
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return preserve_fn(wrapped_async_request_handler)
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class HttpServer(object):
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""" Interface for registering callbacks on a HTTP server
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"""
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def register_paths(self, method, path_patterns, callback):
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""" Register a callback that gets fired if we receive a http request
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with the given method for a path that matches the given regex.
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If the regex contains groups these gets passed to the calback via
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an unpacked tuple.
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Args:
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method (str): The method to listen to.
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path_patterns (list<SRE_Pattern>): The regex used to match requests.
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callback (function): The function to fire if we receive a matched
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request. The first argument will be the request object and
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subsequent arguments will be any matched groups from the regex.
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This should return a tuple of (code, response).
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"""
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pass
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class JsonResource(HttpServer, resource.Resource):
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""" This implements the HttpServer interface and provides JSON support for
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Resources.
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Register callbacks via register_paths()
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Callbacks can return a tuple of status code and a dict in which case the
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the dict will automatically be sent to the client as a JSON object.
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The JsonResource is primarily intended for returning JSON, but callbacks
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may send something other than JSON, they may do so by using the methods
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on the request object and instead returning None.
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"""
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isLeaf = True
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_PathEntry = collections.namedtuple("_PathEntry", ["pattern", "callback"])
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def __init__(self, hs, canonical_json=True):
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resource.Resource.__init__(self)
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self.canonical_json = canonical_json
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self.clock = hs.get_clock()
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self.path_regexs = {}
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self.hs = hs
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def register_paths(self, method, path_patterns, callback):
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method = method.encode("utf-8") # method is bytes on py3
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for path_pattern in path_patterns:
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logger.debug("Registering for %s %s", method, path_pattern.pattern)
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self.path_regexs.setdefault(method, []).append(
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self._PathEntry(path_pattern, callback)
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)
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def render(self, request):
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""" This gets called by twisted every time someone sends us a request.
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"""
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self._async_render(request)
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return NOT_DONE_YET
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@wrap_json_request_handler
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@defer.inlineCallbacks
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def _async_render(self, request):
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""" This gets called from render() every time someone sends us a request.
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This checks if anyone has registered a callback for that method and
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path.
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"""
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callback, group_dict = self._get_handler_for_request(request)
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servlet_instance = getattr(callback, "__self__", None)
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if servlet_instance is not None:
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servlet_classname = servlet_instance.__class__.__name__
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else:
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servlet_classname = "%r" % callback
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request.request_metrics.name = servlet_classname
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# Now trigger the callback. If it returns a response, we send it
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# here. If it throws an exception, that is handled by the wrapper
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# installed by @request_handler.
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def _unquote(s):
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if PY3:
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# On Python 3, unquote is unicode -> unicode
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return urllib.parse.unquote(s)
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else:
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# On Python 2, unquote is bytes -> bytes We need to encode the
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# URL again (as it was decoded by _get_handler_for request), as
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# ASCII because it's a URL, and then decode it to get the UTF-8
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# characters that were quoted.
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return urllib.parse.unquote(s.encode('ascii')).decode('utf8')
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kwargs = intern_dict({
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name: _unquote(value) if value else value
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for name, value in group_dict.items()
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})
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callback_return = yield callback(request, **kwargs)
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if callback_return is not None:
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code, response = callback_return
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self._send_response(request, code, response)
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def _get_handler_for_request(self, request):
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"""Finds a callback method to handle the given request
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Args:
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request (twisted.web.http.Request):
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Returns:
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Tuple[Callable, dict[unicode, unicode]]: callback method, and the
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dict mapping keys to path components as specified in the
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handler's path match regexp.
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The callback will normally be a method registered via
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register_paths, so will return (possibly via Deferred) either
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None, or a tuple of (http code, response body).
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"""
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if request.method == b"OPTIONS":
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return _options_handler, {}
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# Loop through all the registered callbacks to check if the method
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# and path regex match
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for path_entry in self.path_regexs.get(request.method, []):
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m = path_entry.pattern.match(request.path.decode('ascii'))
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if m:
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# We found a match!
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return path_entry.callback, m.groupdict()
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# Huh. No one wanted to handle that? Fiiiiiine. Send 400.
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return _unrecognised_request_handler, {}
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def _send_response(self, request, code, response_json_object,
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response_code_message=None):
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# TODO: Only enable CORS for the requests that need it.
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respond_with_json(
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request, code, response_json_object,
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send_cors=True,
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response_code_message=response_code_message,
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pretty_print=_request_user_agent_is_curl(request),
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canonical_json=self.canonical_json,
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)
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def _options_handler(request):
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"""Request handler for OPTIONS requests
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This is a request handler suitable for return from
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_get_handler_for_request. It returns a 200 and an empty body.
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Args:
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request (twisted.web.http.Request):
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Returns:
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Tuple[int, dict]: http code, response body.
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"""
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return 200, {}
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def _unrecognised_request_handler(request):
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"""Request handler for unrecognised requests
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This is a request handler suitable for return from
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_get_handler_for_request. It actually just raises an
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UnrecognizedRequestError.
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Args:
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request (twisted.web.http.Request):
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"""
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raise UnrecognizedRequestError()
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class RootRedirect(resource.Resource):
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"""Redirects the root '/' path to another path."""
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def __init__(self, path):
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resource.Resource.__init__(self)
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self.url = path
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def render_GET(self, request):
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return redirectTo(self.url.encode('ascii'), request)
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def getChild(self, name, request):
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if len(name) == 0:
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return self # select ourselves as the child to render
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return resource.Resource.getChild(self, name, request)
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def respond_with_json(request, code, json_object, send_cors=False,
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response_code_message=None, pretty_print=False,
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canonical_json=True):
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# could alternatively use request.notifyFinish() and flip a flag when
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# the Deferred fires, but since the flag is RIGHT THERE it seems like
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# a waste.
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if request._disconnected:
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logger.warn(
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"Not sending response to request %s, already disconnected.",
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request)
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return
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if pretty_print:
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json_bytes = encode_pretty_printed_json(json_object) + b"\n"
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else:
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if canonical_json or synapse.events.USE_FROZEN_DICTS:
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# canonicaljson already encodes to bytes
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json_bytes = encode_canonical_json(json_object)
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else:
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json_bytes = json.dumps(json_object).encode("utf-8")
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return respond_with_json_bytes(
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request, code, json_bytes,
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send_cors=send_cors,
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response_code_message=response_code_message,
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)
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def respond_with_json_bytes(request, code, json_bytes, send_cors=False,
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response_code_message=None):
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"""Sends encoded JSON in response to the given request.
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Args:
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request (twisted.web.http.Request): The http request to respond to.
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code (int): The HTTP response code.
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json_bytes (bytes): The json bytes to use as the response body.
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send_cors (bool): Whether to send Cross-Origin Resource Sharing headers
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http://www.w3.org/TR/cors/
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Returns:
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twisted.web.server.NOT_DONE_YET"""
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request.setResponseCode(code, message=response_code_message)
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request.setHeader(b"Content-Type", b"application/json")
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request.setHeader(b"Content-Length", b"%d" % (len(json_bytes),))
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request.setHeader(b"Cache-Control", b"no-cache, no-store, must-revalidate")
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if send_cors:
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set_cors_headers(request)
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# todo: we can almost certainly avoid this copy and encode the json straight into
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# the bytesIO, but it would involve faffing around with string->bytes wrappers.
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bytes_io = BytesIO(json_bytes)
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producer = NoRangeStaticProducer(request, bytes_io)
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producer.start()
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return NOT_DONE_YET
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def set_cors_headers(request):
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"""Set the CORs headers so that javascript running in a web browsers can
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use this API
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Args:
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request (twisted.web.http.Request): The http request to add CORs to.
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"""
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request.setHeader("Access-Control-Allow-Origin", "*")
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request.setHeader(
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"Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS"
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)
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request.setHeader(
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"Access-Control-Allow-Headers",
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"Origin, X-Requested-With, Content-Type, Accept, Authorization"
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)
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def finish_request(request):
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""" Finish writing the response to the request.
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Twisted throws a RuntimeException if the connection closed before the
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response was written but doesn't provide a convenient or reliable way to
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determine if the connection was closed. So we catch and log the RuntimeException
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You might think that ``request.notifyFinish`` could be used to tell if the
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request was finished. However the deferred it returns won't fire if the
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connection was already closed, meaning we'd have to have called the method
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right at the start of the request. By the time we want to write the response
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it will already be too late.
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"""
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try:
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request.finish()
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except RuntimeError as e:
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logger.info("Connection disconnected before response was written: %r", e)
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def _request_user_agent_is_curl(request):
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user_agents = request.requestHeaders.getRawHeaders(
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b"User-Agent", default=[]
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)
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for user_agent in user_agents:
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if b"curl" in user_agent:
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return True
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return False
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