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