Error {code}

# # This file is licensed under the Affero General Public License (AGPL) version 3. # # Copyright (C) 2023 New Vector, Ltd # # This program is free software: you can redistribute it and/or modify # it under the terms of the GNU Affero General Public License as # published by the Free Software Foundation, either version 3 of the # License, or (at your option) any later version. # # See the GNU Affero General Public License for more details: # . # # Originally licensed under the Apache License, Version 2.0: # . # # [This file includes modifications made by New Vector Limited] # # import abc import html import logging import types import urllib import urllib.parse from http import HTTPStatus from http.client import FOUND from inspect import isawaitable from typing import ( TYPE_CHECKING, Any, Awaitable, Callable, Dict, Iterable, Iterator, List, Optional, Pattern, Tuple, Union, ) import attr import jinja2 from canonicaljson import encode_canonical_json from typing_extensions import Protocol from zope.interface import implementer from twisted.internet import defer, interfaces from twisted.internet.defer import CancelledError from twisted.python import failure from twisted.web import resource try: from twisted.web.pages import notFound except ImportError: from twisted.web.resource import NoResource as notFound # type: ignore[assignment] from twisted.web.resource import IResource from twisted.web.server import NOT_DONE_YET, Request from twisted.web.static import File from twisted.web.util import redirectTo from synapse.api.errors import ( CodeMessageException, Codes, RedirectException, SynapseError, UnrecognizedRequestError, ) from synapse.config.homeserver import HomeServerConfig from synapse.logging.context import defer_to_thread, preserve_fn, run_in_background from synapse.logging.opentracing import active_span, start_active_span, trace_servlet from synapse.util import json_encoder from synapse.util.caches import intern_dict from synapse.util.cancellation import is_function_cancellable from synapse.util.iterutils import chunk_seq if TYPE_CHECKING: import opentracing from synapse.http.site import SynapseRequest from synapse.server import HomeServer logger = logging.getLogger(__name__) HTML_ERROR_TEMPLATE = """ Error {code}

{msg}

""" # A fictional HTTP status code for requests where the client has disconnected and we # successfully cancelled the request. Used only for logging purposes. Clients will never # observe this code unless cancellations leak across requests or we raise a # `CancelledError` ourselves. # Analogous to nginx's 499 status code: # https://github.com/nginx/nginx/blob/release-1.21.6/src/http/ngx_http_request.h#L128-L134 HTTP_STATUS_REQUEST_CANCELLED = 499 def return_json_error( f: failure.Failure, request: "SynapseRequest", config: Optional[HomeServerConfig] ) -> None: """Sends a JSON error response to clients.""" if f.check(SynapseError): # mypy doesn't understand that f.check asserts the type. exc: SynapseError = f.value error_code = exc.code error_dict = exc.error_dict(config) if exc.headers is not None: for header, value in exc.headers.items(): request.setHeader(header, value) error_ctx = exc.debug_context if error_ctx: logger.info( "%s SynapseError: %s - %s (%s)", request, error_code, exc.msg, error_ctx ) else: logger.info("%s SynapseError: %s - %s", request, error_code, exc.msg) elif f.check(CancelledError): error_code = HTTP_STATUS_REQUEST_CANCELLED error_dict = {"error": "Request cancelled", "errcode": Codes.UNKNOWN} if not request._disconnected: logger.error( "Got cancellation before client disconnection from %r: %r", request.request_metrics.name, request, exc_info=(f.type, f.value, f.getTracebackObject()), ) else: error_code = 500 error_dict = {"error": "Internal server error", "errcode": Codes.UNKNOWN} logger.error( "Failed handle request via %r: %r", request.request_metrics.name, request, exc_info=(f.type, f.value, f.getTracebackObject()), ) # Only respond with an error response if we haven't already started writing, # otherwise lets just kill the connection if request.startedWriting: if request.transport: try: request.transport.abortConnection() except Exception: # abortConnection throws if the connection is already closed pass else: respond_with_json( request, error_code, error_dict, send_cors=True, ) def return_html_error( f: failure.Failure, request: Request, error_template: Union[str, jinja2.Template], ) -> None: """Sends an HTML error page corresponding to the given failure. Handles RedirectException and other CodeMessageExceptions (such as SynapseError) Args: f: the error to report request: the failing request error_template: the HTML template. Can be either a string (with `{code}`, `{msg}` placeholders), or a jinja2 template """ if f.check(CodeMessageException): # mypy doesn't understand that f.check asserts the type. cme: CodeMessageException = f.value code = cme.code msg = cme.msg if cme.headers is not None: for header, value in cme.headers.items(): request.setHeader(header, value) if isinstance(cme, RedirectException): logger.info("%s redirect to %s", request, cme.location) request.setHeader(b"location", cme.location) request.cookies.extend(cme.cookies) elif isinstance(cme, SynapseError): logger.info("%s SynapseError: %s - %s", request, code, msg) else: logger.error( "Failed handle request %r", request, exc_info=(f.type, f.value, f.getTracebackObject()), ) elif f.check(CancelledError): code = HTTP_STATUS_REQUEST_CANCELLED msg = "Request cancelled" if not request._disconnected: logger.error( "Got cancellation before client disconnection when handling request %r", request, exc_info=(f.type, f.value, f.getTracebackObject()), ) else: code = HTTPStatus.INTERNAL_SERVER_ERROR msg = "Internal server error" logger.error( "Failed handle request %r", request, exc_info=(f.type, f.value, f.getTracebackObject()), ) if isinstance(error_template, str): body = error_template.format(code=code, msg=html.escape(msg)) else: body = error_template.render(code=code, msg=msg) respond_with_html(request, code, body) def wrap_async_request_handler( h: Callable[["_AsyncResource", "SynapseRequest"], Awaitable[None]] ) -> Callable[["_AsyncResource", "SynapseRequest"], "defer.Deferred[None]"]: """Wraps an async request handler so that it calls request.processing. This helps ensure that work done by the request handler after the request is completed is correctly recorded against the request metrics/logs. The handler method must have a signature of "handle_foo(self, request)", where "request" must be a SynapseRequest. The handler may return a deferred, in which case the completion of the request isn't logged until the deferred completes. """ async def wrapped_async_request_handler( self: "_AsyncResource", request: "SynapseRequest" ) -> None: with request.processing(): await h(self, request) # we need to preserve_fn here, because the synchronous render method won't yield for # us (obviously) return preserve_fn(wrapped_async_request_handler) # Type of a callback method for processing requests # it is actually called with a SynapseRequest and a kwargs dict for the params, # but I can't figure out how to represent that. ServletCallback = Callable[ ..., Union[None, Awaitable[None], Tuple[int, Any], Awaitable[Tuple[int, Any]]] ] class HttpServer(Protocol): """Interface for registering callbacks on a HTTP server""" def register_paths( self, method: str, path_patterns: Iterable[Pattern[str]], callback: ServletCallback, servlet_classname: str, ) -> None: """Register a callback that gets fired if we receive a http request with the given method for a path that matches the given regex. If the regex contains groups these gets passed to the callback via an unpacked tuple. The callback may be marked with the `@cancellable` decorator, which will cause request processing to be cancelled when clients disconnect early. Args: method: The HTTP method to listen to. path_patterns: The regex used to match requests. callback: The function to fire if we receive a matched request. The first argument will be the request object and subsequent arguments will be any matched groups from the regex. This should return either tuple of (code, response), or None. servlet_classname: The name of the handler to be used in prometheus and opentracing logs. """ class _AsyncResource(resource.Resource, metaclass=abc.ABCMeta): """Base class for resources that have async handlers. Sub classes can either implement `_async_render_` to handle requests by method, or override `_async_render` to handle all requests. Args: extract_context: Whether to attempt to extract the opentracing context from the request the servlet is handling. """ def __init__(self, extract_context: bool = False): super().__init__() self._extract_context = extract_context def render(self, request: "SynapseRequest") -> int: """This gets called by twisted every time someone sends us a request.""" request.render_deferred = defer.ensureDeferred( self._async_render_wrapper(request) ) return NOT_DONE_YET @wrap_async_request_handler async def _async_render_wrapper(self, request: "SynapseRequest") -> None: """This is a wrapper that delegates to `_async_render` and handles exceptions, return values, metrics, etc. """ try: request.request_metrics.name = self.__class__.__name__ with trace_servlet(request, self._extract_context): callback_return = await self._async_render(request) if callback_return is not None: code, response = callback_return self._send_response(request, code, response) except Exception: # failure.Failure() fishes the original Failure out # of our stack, and thus gives us a sensible stack # trace. f = failure.Failure() self._send_error_response(f, request) async def _async_render( self, request: "SynapseRequest" ) -> Optional[Tuple[int, Any]]: """Delegates to `_async_render_` methods, or returns a 400 if no appropriate method exists. Can be overridden in sub classes for different routing. """ # Treat HEAD requests as GET requests. request_method = request.method.decode("ascii") if request_method == "HEAD": request_method = "GET" method_handler = getattr(self, "_async_render_%s" % (request_method,), None) if method_handler: request.is_render_cancellable = is_function_cancellable(method_handler) raw_callback_return = method_handler(request) # Is it synchronous? We'll allow this for now. if isawaitable(raw_callback_return): callback_return = await raw_callback_return else: callback_return = raw_callback_return return callback_return # A request with an unknown method (for a known endpoint) was received. raise UnrecognizedRequestError(code=405) @abc.abstractmethod def _send_response( self, request: "SynapseRequest", code: int, response_object: Any, ) -> None: raise NotImplementedError() @abc.abstractmethod def _send_error_response( self, f: failure.Failure, request: "SynapseRequest", ) -> None: raise NotImplementedError() class DirectServeJsonResource(_AsyncResource): """A resource that will call `self._async_on_` on new requests, formatting responses and errors as JSON. """ def __init__(self, canonical_json: bool = False, extract_context: bool = False): super().__init__(extract_context) self.canonical_json = canonical_json def _send_response( self, request: "SynapseRequest", code: int, response_object: Any, ) -> None: """Implements _AsyncResource._send_response""" # TODO: Only enable CORS for the requests that need it. respond_with_json( request, code, response_object, send_cors=True, canonical_json=self.canonical_json, ) def _send_error_response( self, f: failure.Failure, request: "SynapseRequest", ) -> None: """Implements _AsyncResource._send_error_response""" return_json_error(f, request, None) @attr.s(slots=True, frozen=True, auto_attribs=True) class _PathEntry: callback: ServletCallback servlet_classname: str class JsonResource(DirectServeJsonResource): """This implements the HttpServer interface and provides JSON support for Resources. Register callbacks via register_paths() Callbacks can return a tuple of status code and a dict in which case the the dict will automatically be sent to the client as a JSON object. The JsonResource is primarily intended for returning JSON, but callbacks may send something other than JSON, they may do so by using the methods on the request object and instead returning None. """ isLeaf = True def __init__( self, hs: "HomeServer", canonical_json: bool = True, extract_context: bool = False, ): super().__init__(canonical_json, extract_context) self.clock = hs.get_clock() # Map of path regex -> method -> callback. self._routes: Dict[Pattern[str], Dict[bytes, _PathEntry]] = {} self.hs = hs def register_paths( self, method: str, path_patterns: Iterable[Pattern[str]], callback: ServletCallback, servlet_classname: str, ) -> None: """ Registers a request handler against a regular expression. Later request URLs are checked against these regular expressions in order to identify an appropriate handler for that request. Args: method: GET, POST etc path_patterns: A list of regular expressions to which the request URLs are compared. callback: The handler for the request. Usually a Servlet servlet_classname: The name of the handler to be used in prometheus and opentracing logs. """ method_bytes = method.encode("utf-8") for path_pattern in path_patterns: logger.debug("Registering for %s %s", method, path_pattern.pattern) self._routes.setdefault(path_pattern, {})[method_bytes] = _PathEntry( callback, servlet_classname ) def _get_handler_for_request( self, request: "SynapseRequest" ) -> Tuple[ServletCallback, str, Dict[str, str]]: """Finds a callback method to handle the given request. Returns: A tuple of the callback to use, the name of the servlet, and the key word arguments to pass to the callback """ # At this point the path must be bytes. request_path_bytes: bytes = request.path # type: ignore request_path = request_path_bytes.decode("ascii") # Treat HEAD requests as GET requests. request_method = request.method if request_method == b"HEAD": request_method = b"GET" # Loop through all the registered callbacks to check if the method # and path regex match for path_pattern, methods in self._routes.items(): m = path_pattern.match(request_path) if m: # We found a matching path! path_entry = methods.get(request_method) if not path_entry: raise UnrecognizedRequestError(code=405) return path_entry.callback, path_entry.servlet_classname, m.groupdict() # Huh. No one wanted to handle that? Fiiiiiine. raise UnrecognizedRequestError(code=404) async def _async_render(self, request: "SynapseRequest") -> Tuple[int, Any]: callback, servlet_classname, group_dict = self._get_handler_for_request(request) request.is_render_cancellable = is_function_cancellable(callback) # Make sure we have an appropriate name for this handler in prometheus # (rather than the default of JsonResource). request.request_metrics.name = servlet_classname # Now trigger the callback. If it returns a response, we send it # here. If it throws an exception, that is handled by the wrapper # installed by @request_handler. kwargs = intern_dict( { name: urllib.parse.unquote(value) if value else value for name, value in group_dict.items() } ) raw_callback_return = callback(request, **kwargs) # Is it synchronous? We'll allow this for now. if isinstance(raw_callback_return, (defer.Deferred, types.CoroutineType)): callback_return = await raw_callback_return else: callback_return = raw_callback_return return callback_return def _send_error_response( self, f: failure.Failure, request: "SynapseRequest", ) -> None: """Implements _AsyncResource._send_error_response""" return_json_error(f, request, self.hs.config) class DirectServeHtmlResource(_AsyncResource): """A resource that will call `self._async_on_` on new requests, formatting responses and errors as HTML. """ # The error template to use for this resource ERROR_TEMPLATE = HTML_ERROR_TEMPLATE def _send_response( self, request: "SynapseRequest", code: int, response_object: Any, ) -> None: """Implements _AsyncResource._send_response""" # We expect to get bytes for us to write assert isinstance(response_object, bytes) html_bytes = response_object respond_with_html_bytes(request, 200, html_bytes) def _send_error_response( self, f: failure.Failure, request: "SynapseRequest", ) -> None: """Implements _AsyncResource._send_error_response""" return_html_error(f, request, self.ERROR_TEMPLATE) class StaticResource(File): """ A resource that represents a plain non-interpreted file or directory. Differs from the File resource by adding clickjacking protection. """ def render_GET(self, request: Request) -> bytes: set_clickjacking_protection_headers(request) return super().render_GET(request) def directoryListing(self) -> IResource: return notFound() class UnrecognizedRequestResource(resource.Resource): """ Similar to twisted.web.resource.NoResource, but returns a JSON 404 with an errcode of M_UNRECOGNIZED. """ def render(self, request: "SynapseRequest") -> int: f = failure.Failure(UnrecognizedRequestError(code=404)) return_json_error(f, request, None) # A response has already been sent but Twisted requires either NOT_DONE_YET # or the response bytes as a return value. return NOT_DONE_YET def getChild(self, name: str, request: Request) -> resource.Resource: return self class RootRedirect(resource.Resource): """Redirects the root '/' path to another path.""" def __init__(self, path: str): super().__init__() self.url = path def render_GET(self, request: Request) -> bytes: return redirectTo(self.url.encode("ascii"), request) def getChild(self, name: str, request: Request) -> resource.Resource: if len(name) == 0: return self # select ourselves as the child to render return super().getChild(name, request) class OptionsResource(resource.Resource): """Responds to OPTION requests for itself and all children.""" def render_OPTIONS(self, request: "SynapseRequest") -> bytes: request.setResponseCode(204) request.setHeader(b"Content-Length", b"0") set_cors_headers(request) return b"" def getChildWithDefault(self, path: str, request: Request) -> resource.Resource: if request.method == b"OPTIONS": return self # select ourselves as the child to render return super().getChildWithDefault(path, request) class RootOptionsRedirectResource(OptionsResource, RootRedirect): pass @implementer(interfaces.IPushProducer) class _ByteProducer: """ Iteratively write bytes to the request. """ # The minimum number of bytes for each chunk. Note that the last chunk will # usually be smaller than this. min_chunk_size = 1024 def __init__( self, request: Request, iterator: Iterator[bytes], ): self._request: Optional[Request] = request self._iterator = iterator self._paused = False try: self._request.registerProducer(self, True) except AttributeError as e: # Calling self._request.registerProducer might raise an AttributeError since # the underlying Twisted code calls self._request.channel.registerProducer, # however self._request.channel will be None if the connection was lost. logger.info("Connection disconnected before response was written: %r", e) # We drop our references to data we'll not use. self._request = None self._iterator = iter(()) else: # Start producing if `registerProducer` was successful self.resumeProducing() def _send_data(self, data: List[bytes]) -> None: """ Send a list of bytes as a chunk of a response. """ if not data or not self._request: return self._request.write(b"".join(data)) def pauseProducing(self) -> None: self._paused = True def resumeProducing(self) -> None: # We've stopped producing in the meantime (note that this might be # re-entrant after calling write). if not self._request: return self._paused = False # Write until there's backpressure telling us to stop. while not self._paused: # Get the next chunk and write it to the request. # # The output of the JSON encoder is buffered and coalesced until # min_chunk_size is reached. This is because JSON encoders produce # very small output per iteration and the Request object converts # each call to write() to a separate chunk. Without this there would # be an explosion in bytes written (e.g. b"{" becoming "1\r\n{\r\n"). # # Note that buffer stores a list of bytes (instead of appending to # bytes) to hopefully avoid many allocations. buffer = [] buffered_bytes = 0 while buffered_bytes < self.min_chunk_size: try: data = next(self._iterator) buffer.append(data) buffered_bytes += len(data) except StopIteration: # The entire JSON object has been serialized, write any # remaining data, finalize the producer and the request, and # clean-up any references. self._send_data(buffer) self._request.unregisterProducer() self._request.finish() self.stopProducing() return self._send_data(buffer) def stopProducing(self) -> None: # Clear a circular reference. self._request = None def _encode_json_bytes(json_object: object) -> bytes: """ Encode an object into JSON. Returns an iterator of bytes. """ return json_encoder.encode(json_object).encode("utf-8") def respond_with_json( request: "SynapseRequest", code: int, json_object: Any, send_cors: bool = False, canonical_json: bool = True, ) -> Optional[int]: """Sends encoded JSON in response to the given request. Args: request: The http request to respond to. code: The HTTP response code. json_object: The object to serialize to JSON. send_cors: Whether to send Cross-Origin Resource Sharing headers https://fetch.spec.whatwg.org/#http-cors-protocol canonical_json: Whether to use the canonicaljson algorithm when encoding the JSON bytes. Returns: twisted.web.server.NOT_DONE_YET if the request is still active. """ # The response code must always be set, for logging purposes. request.setResponseCode(code) # could alternatively use request.notifyFinish() and flip a flag when # the Deferred fires, but since the flag is RIGHT THERE it seems like # a waste. if request._disconnected: logger.warning( "Not sending response to request %s, already disconnected.", request ) return None if canonical_json: encoder: Callable[[object], bytes] = encode_canonical_json else: encoder = _encode_json_bytes request.setHeader(b"Content-Type", b"application/json") request.setHeader(b"Cache-Control", b"no-cache, no-store, must-revalidate") if send_cors: set_cors_headers(request) run_in_background( _async_write_json_to_request_in_thread, request, encoder, json_object ) return NOT_DONE_YET def respond_with_json_bytes( request: "SynapseRequest", code: int, json_bytes: bytes, send_cors: bool = False, ) -> Optional[int]: """Sends encoded JSON in response to the given request. Args: request: The http request to respond to. code: The HTTP response code. json_bytes: The json bytes to use as the response body. send_cors: Whether to send Cross-Origin Resource Sharing headers https://fetch.spec.whatwg.org/#http-cors-protocol Returns: twisted.web.server.NOT_DONE_YET if the request is still active. """ # The response code must always be set, for logging purposes. request.setResponseCode(code) if request._disconnected: logger.warning( "Not sending response to request %s, already disconnected.", request ) return None request.setHeader(b"Content-Type", b"application/json") request.setHeader(b"Content-Length", b"%d" % (len(json_bytes),)) request.setHeader(b"Cache-Control", b"no-cache, no-store, must-revalidate") if send_cors: set_cors_headers(request) _write_bytes_to_request(request, json_bytes) return NOT_DONE_YET async def _async_write_json_to_request_in_thread( request: "SynapseRequest", json_encoder: Callable[[Any], bytes], json_object: Any, ) -> None: """Encodes the given JSON object on a thread and then writes it to the request. This is done so that encoding large JSON objects doesn't block the reactor thread. Note: We don't use JsonEncoder.iterencode here as that falls back to the Python implementation (rather than the C backend), which is *much* more expensive. """ def encode(opentracing_span: "Optional[opentracing.Span]") -> bytes: # it might take a while for the threadpool to schedule us, so we write # opentracing logs once we actually get scheduled, so that we can see how # much that contributed. if opentracing_span: opentracing_span.log_kv({"event": "scheduled"}) res = json_encoder(json_object) if opentracing_span: opentracing_span.log_kv({"event": "encoded"}) return res with start_active_span("encode_json_response"): span = active_span() json_str = await defer_to_thread(request.reactor, encode, span) _write_bytes_to_request(request, json_str) def _write_bytes_to_request(request: Request, bytes_to_write: bytes) -> None: """Writes the bytes to the request using an appropriate producer. Note: This should be used instead of `Request.write` to correctly handle large response bodies. """ # The problem with dumping all of the response into the `Request` object at # once (via `Request.write`) is that doing so starts the timeout for the # next request to be received: so if it takes longer than 60s to stream back # the response to the client, the client never gets it. # # The correct solution is to use a Producer; then the timeout is only # started once all of the content is sent over the TCP connection. # To make sure we don't write all of the bytes at once we split it up into # chunks. chunk_size = 4096 bytes_generator = chunk_seq(bytes_to_write, chunk_size) # We use a `_ByteProducer` here rather than `NoRangeStaticProducer` as the # unit tests can't cope with being given a pull producer. _ByteProducer(request, bytes_generator) def set_cors_headers(request: "SynapseRequest") -> None: """Set the CORS headers so that javascript running in a web browsers can use this API Args: request: The http request to add CORS to. """ request.setHeader(b"Access-Control-Allow-Origin", b"*") request.setHeader( b"Access-Control-Allow-Methods", b"GET, HEAD, POST, PUT, DELETE, OPTIONS" ) if request.experimental_cors_msc3886: request.setHeader( b"Access-Control-Allow-Headers", b"X-Requested-With, Content-Type, Authorization, Date, If-Match, If-None-Match", ) request.setHeader( b"Access-Control-Expose-Headers", b"ETag, Location, X-Max-Bytes", ) else: request.setHeader( b"Access-Control-Allow-Headers", b"X-Requested-With, Content-Type, Authorization, Date", ) request.setHeader( b"Access-Control-Expose-Headers", b"Synapse-Trace-Id, Server", ) def set_corp_headers(request: Request) -> None: """Set the CORP headers so that javascript running in a web browsers can embed the resource returned from this request when their client requires the `Cross-Origin-Embedder-Policy: require-corp` header. Args: request: The http request to add the CORP header to. """ request.setHeader(b"Cross-Origin-Resource-Policy", b"cross-origin") def respond_with_html(request: Request, code: int, html: str) -> None: """ Wraps `respond_with_html_bytes` by first encoding HTML from a str to UTF-8 bytes. """ respond_with_html_bytes(request, code, html.encode("utf-8")) def respond_with_html_bytes(request: Request, code: int, html_bytes: bytes) -> None: """ Sends HTML (encoded as UTF-8 bytes) as the response to the given request. Note that this adds clickjacking protection headers and finishes the request. Args: request: The http request to respond to. code: The HTTP response code. html_bytes: The HTML bytes to use as the response body. """ # The response code must always be set, for logging purposes. request.setResponseCode(code) # could alternatively use request.notifyFinish() and flip a flag when # the Deferred fires, but since the flag is RIGHT THERE it seems like # a waste. if request._disconnected: logger.warning( "Not sending response to request %s, already disconnected.", request ) return None request.setHeader(b"Content-Type", b"text/html; charset=utf-8") request.setHeader(b"Content-Length", b"%d" % (len(html_bytes),)) # Ensure this content cannot be embedded. set_clickjacking_protection_headers(request) request.write(html_bytes) finish_request(request) def set_clickjacking_protection_headers(request: Request) -> None: """ Set headers to guard against clickjacking of embedded content. This sets the X-Frame-Options and Content-Security-Policy headers which instructs browsers to not allow the HTML of the response to be embedded onto another page. Args: request: The http request to add the headers to. """ request.setHeader(b"X-Frame-Options", b"DENY") request.setHeader(b"Content-Security-Policy", b"frame-ancestors 'none';") def respond_with_redirect( request: "SynapseRequest", url: bytes, statusCode: int = FOUND, cors: bool = False ) -> None: """ Write a 302 (or other specified status code) response to the request, if it is still alive. Args: request: The http request to respond to. url: The URL to redirect to. statusCode: The HTTP status code to use for the redirect (defaults to 302). cors: Whether to set CORS headers on the response. """ logger.debug("Redirect to %s", url.decode("utf-8")) if cors: set_cors_headers(request) request.setResponseCode(statusCode) request.setHeader(b"location", url) finish_request(request) def finish_request(request: Request) -> None: """Finish writing the response to the request. Twisted throws a RuntimeException if the connection closed before the response was written but doesn't provide a convenient or reliable way to determine if the connection was closed. So we catch and log the RuntimeException You might think that ``request.notifyFinish`` could be used to tell if the request was finished. However the deferred it returns won't fire if the connection was already closed, meaning we'd have to have called the method right at the start of the request. By the time we want to write the response it will already be too late. """ try: request.finish() except RuntimeError as e: logger.info("Connection disconnected before response was written: %r", e)