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![Richard van der Hoff](/assets/img/avatar_default.png)
This is the first of two PRs which seek to address #8518. This first PR lays the groundwork by extending ResponseCache; a second PR (#10158) will update the SyncHandler to actually use it, and fix the bug. The idea here is that we allow the callback given to ResponseCache.wrap to decide whether its result should be cached or not. We do that by (optionally) passing a ResponseCacheContext into it, which it can modify.
308 lines
12 KiB
Python
308 lines
12 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
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from inspect import signature
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from typing import TYPE_CHECKING, Dict, List, Tuple
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from prometheus_client import Counter, Gauge
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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.logging import opentracing
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from synapse.logging.opentracing import trace
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from synapse.util.caches.response_cache import ResponseCache
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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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"""
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NAME = abc.abstractproperty() # type: str # type: ignore
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PATH_ARGS = abc.abstractproperty() # type: Tuple[str, ...] # 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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def __init__(self, hs: "HomeServer"):
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if self.CACHE:
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self.response_cache = ResponseCache(
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hs.get_clock(), "repl." + self.NAME, timeout_ms=30 * 60 * 1000
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) # type: ResponseCache[str]
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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) -> 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 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):
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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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dict: 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(self, request, **kwargs):
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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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tuple[int, dict]: HTTP status code and a JSON serialisable dict
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to be used as response body of request.
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"""
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pass
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@classmethod
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def make_client(cls, hs):
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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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master_host = hs.config.worker_replication_host
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master_port = hs.config.worker_replication_http_port
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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(opname="outgoing_replication_request")
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@outgoing_gauge.track_inprogress()
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async def send_request(*, instance_name="master", **kwargs):
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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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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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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 = 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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uri = "http://%s:%s/_synapse/replication/%s/%s" % (
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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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try:
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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 on
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# the master, and so whether we should clean up or not.
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while True:
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headers = {} # type: 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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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 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(502, "Failed to talk to main process") 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):
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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:
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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(self, request, **kwargs):
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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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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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return await self._handle_request(request, **kwargs)
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