# 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 abc import logging import re import urllib.parse from inspect import signature from typing import TYPE_CHECKING, Any, Awaitable, Callable, Dict, List, Tuple from prometheus_client import Counter, Gauge from twisted.internet.error import ConnectError, DNSLookupError from twisted.web.server import Request from synapse.api.errors import HttpResponseException, SynapseError from synapse.http import RequestTimedOutError from synapse.http.server import HttpServer from synapse.http.site import SynapseRequest from synapse.logging import opentracing from synapse.logging.opentracing import trace_with_opname from synapse.types import JsonDict from synapse.util.caches.response_cache import ResponseCache from synapse.util.cancellation import is_function_cancellable from synapse.util.stringutils import random_string if TYPE_CHECKING: from synapse.server import HomeServer logger = logging.getLogger(__name__) _pending_outgoing_requests = Gauge( "synapse_pending_outgoing_replication_requests", "Number of active outgoing replication requests, by replication method name", ["name"], ) _outgoing_request_counter = Counter( "synapse_outgoing_replication_requests", "Number of outgoing replication requests, by replication method name and result", ["name", "code"], ) class ReplicationEndpoint(metaclass=abc.ABCMeta): """Helper base class for defining new replication HTTP endpoints. This creates an endpoint under `/_synapse/replication/:NAME/:PATH_ARGS..` (with a `/:txn_id` suffix for cached requests), where NAME is a name, PATH_ARGS are a tuple of parameters to be encoded in the URL. For example, if `NAME` is "send_event" and `PATH_ARGS` is `("event_id",)`, with `CACHE` set to true then this generates an endpoint: /_synapse/replication/send_event/:event_id/:txn_id For POST/PUT requests the payload is serialized to json and sent as the body, while for GET requests the payload is added as query parameters. See `_serialize_payload` for details. Incoming requests are handled by overriding `_handle_request`. Servers must call `register` to register the path with the HTTP server. Requests can be sent by calling the client returned by `make_client`. Requests are sent to master process by default, but can be sent to other named processes by specifying an `instance_name` keyword argument. Attributes: NAME (str): A name for the endpoint, added to the path as well as used in logging and metrics. PATH_ARGS (tuple[str]): A list of parameters to be added to the path. Adding parameters to the path (rather than payload) can make it easier to follow along in the log files. METHOD (str): The method of the HTTP request, defaults to POST. Can be one of POST, PUT or GET. If GET then the payload is sent as query parameters rather than a JSON body. CACHE (bool): Whether server should cache the result of the request/ If true then transparently adds a txn_id to all requests, and `_handle_request` must return a Deferred. RETRY_ON_TIMEOUT(bool): Whether or not to retry the request when a 504 is received. RETRY_ON_CONNECT_ERROR (bool): Whether or not to retry the request when a connection error is received. RETRY_ON_CONNECT_ERROR_ATTEMPTS (int): Number of attempts to retry when receiving connection errors, each will backoff exponentially longer. """ NAME: str = abc.abstractproperty() # type: ignore PATH_ARGS: Tuple[str, ...] = abc.abstractproperty() # type: ignore METHOD = "POST" CACHE = True RETRY_ON_TIMEOUT = True RETRY_ON_CONNECT_ERROR = True RETRY_ON_CONNECT_ERROR_ATTEMPTS = 5 # =63s (2^6-1) def __init__(self, hs: "HomeServer"): if self.CACHE: self.response_cache: ResponseCache[str] = ResponseCache( hs.get_clock(), "repl." + self.NAME, timeout_ms=30 * 60 * 1000 ) # We reserve `instance_name` as a parameter to sending requests, so we # assert here that sub classes don't try and use the name. assert ( "instance_name" not in self.PATH_ARGS ), "`instance_name` is a reserved parameter name" assert ( "instance_name" not in signature(self.__class__._serialize_payload).parameters ), "`instance_name` is a reserved parameter name" assert self.METHOD in ("PUT", "POST", "GET") self._replication_secret = None if hs.config.worker.worker_replication_secret: self._replication_secret = hs.config.worker.worker_replication_secret def _check_auth(self, request: Request) -> None: # Get the authorization header. auth_headers = request.requestHeaders.getRawHeaders(b"Authorization") if not auth_headers: raise RuntimeError("Missing Authorization header.") if len(auth_headers) > 1: raise RuntimeError("Too many Authorization headers.") parts = auth_headers[0].split(b" ") if parts[0] == b"Bearer" and len(parts) == 2: received_secret = parts[1].decode("ascii") if self._replication_secret == received_secret: # Success! return raise RuntimeError("Invalid Authorization header.") @abc.abstractmethod async def _serialize_payload(**kwargs) -> JsonDict: """Static method that is called when creating a request. Concrete implementations should have explicit parameters (rather than kwargs) so that an appropriate exception is raised if the client is called with unexpected parameters. All PATH_ARGS must appear in argument list. Returns: dict: If POST/PUT request then dictionary must be JSON serialisable, otherwise must be appropriate for adding as query args. """ return {} @abc.abstractmethod async def _handle_request( self, request: Request, **kwargs: Any ) -> Tuple[int, JsonDict]: """Handle incoming request. This is called with the request object and PATH_ARGS. Returns: HTTP status code and a JSON serialisable dict to be used as response body of request. """ @classmethod def make_client(cls, hs: "HomeServer") -> Callable: """Create a client that makes requests. Returns a callable that accepts the same parameters as `_serialize_payload`, and also accepts an optional `instance_name` parameter to specify which instance to hit (the instance must be in the `instance_map` config). """ clock = hs.get_clock() client = hs.get_simple_http_client() local_instance_name = hs.get_instance_name() # The value of these option should match the replication listener settings master_host = hs.config.worker.worker_replication_host master_port = hs.config.worker.worker_replication_http_port master_tls = hs.config.worker.worker_replication_http_tls instance_map = hs.config.worker.instance_map outgoing_gauge = _pending_outgoing_requests.labels(cls.NAME) replication_secret = None if hs.config.worker.worker_replication_secret: replication_secret = hs.config.worker.worker_replication_secret.encode( "ascii" ) @trace_with_opname("outgoing_replication_request") async def send_request(*, instance_name: str = "master", **kwargs: Any) -> Any: with outgoing_gauge.track_inprogress(): if instance_name == local_instance_name: raise Exception("Trying to send HTTP request to self") if instance_name == "master": host = master_host port = master_port tls = master_tls elif instance_name in instance_map: host = instance_map[instance_name].host port = instance_map[instance_name].port tls = instance_map[instance_name].tls else: raise Exception( "Instance %r not in 'instance_map' config" % (instance_name,) ) data = await cls._serialize_payload(**kwargs) url_args = [ urllib.parse.quote(kwargs[name], safe="") for name in cls.PATH_ARGS ] if cls.CACHE: txn_id = random_string(10) url_args.append(txn_id) if cls.METHOD == "POST": request_func: Callable[ ..., Awaitable[Any] ] = client.post_json_get_json elif cls.METHOD == "PUT": request_func = client.put_json elif cls.METHOD == "GET": request_func = client.get_json else: # We have already asserted in the constructor that a # compatible was picked, but lets be paranoid. raise Exception( "Unknown METHOD on %s replication endpoint" % (cls.NAME,) ) # Here the protocol is hard coded to be http by default or https in case the replication # port is set to have tls true. scheme = "https" if tls else "http" uri = "%s://%s:%s/_synapse/replication/%s/%s" % ( scheme, host, port, cls.NAME, "/".join(url_args), ) headers: Dict[bytes, List[bytes]] = {} # Add an authorization header, if configured. if replication_secret: headers[b"Authorization"] = [b"Bearer " + replication_secret] opentracing.inject_header_dict(headers, check_destination=False) try: # Keep track of attempts made so we can bail if we don't manage to # connect to the target after N tries. attempts = 0 # We keep retrying the same request for timeouts. This is so that we # have a good idea that the request has either succeeded or failed # on the master, and so whether we should clean up or not. while True: try: result = await request_func(uri, data, headers=headers) break except RequestTimedOutError: if not cls.RETRY_ON_TIMEOUT: raise logger.warning("%s request timed out; retrying", cls.NAME) # If we timed out we probably don't need to worry about backing # off too much, but lets just wait a little anyway. await clock.sleep(1) except (ConnectError, DNSLookupError) as e: if not cls.RETRY_ON_CONNECT_ERROR: raise if attempts > cls.RETRY_ON_CONNECT_ERROR_ATTEMPTS: raise delay = 2**attempts logger.warning( "%s request connection failed; retrying in %ds: %r", cls.NAME, delay, e, ) await clock.sleep(delay) attempts += 1 except HttpResponseException as e: # We convert to SynapseError as we know that it was a SynapseError # on the main process that we should send to the client. (And # importantly, not stack traces everywhere) _outgoing_request_counter.labels(cls.NAME, e.code).inc() raise e.to_synapse_error() except Exception as e: _outgoing_request_counter.labels(cls.NAME, "ERR").inc() raise SynapseError( 502, f"Failed to talk to {instance_name} process" ) from e _outgoing_request_counter.labels(cls.NAME, 200).inc() return result return send_request def register(self, http_server: HttpServer) -> None: """Called by the server to register this as a handler to the appropriate path. """ url_args = list(self.PATH_ARGS) method = self.METHOD if self.CACHE and is_function_cancellable(self._handle_request): raise Exception( f"{self.__class__.__name__} has been marked as cancellable, but CACHE " "is set. The cancellable flag would have no effect." ) if self.CACHE: url_args.append("txn_id") args = "/".join("(?P<%s>[^/]+)" % (arg,) for arg in url_args) pattern = re.compile("^/_synapse/replication/%s/%s$" % (self.NAME, args)) http_server.register_paths( method, [pattern], self._check_auth_and_handle, self.__class__.__name__, ) async def _check_auth_and_handle( self, request: SynapseRequest, **kwargs: Any ) -> Tuple[int, JsonDict]: """Called on new incoming requests when caching is enabled. Checks if there is a cached response for the request and returns that, otherwise calls `_handle_request` and caches its response. """ # We just use the txn_id here, but we probably also want to use the # other PATH_ARGS as well. # Check the authorization headers before handling the request. if self._replication_secret: self._check_auth(request) if self.CACHE: txn_id = kwargs.pop("txn_id") # We ignore the `@cancellable` flag, since cancellation wouldn't interupt # `_handle_request` and `ResponseCache` does not handle cancellation # correctly yet. In particular, there may be issues to do with logging # context lifetimes. return await self.response_cache.wrap( txn_id, self._handle_request, request, **kwargs ) # The `@cancellable` decorator may be applied to `_handle_request`. But we # told `HttpServer.register_paths` that our handler is `_check_auth_and_handle`, # so we have to set up the cancellable flag ourselves. request.is_render_cancellable = is_function_cancellable(self._handle_request) return await self._handle_request(request, **kwargs)