233 lines
8.3 KiB
Python
233 lines
8.3 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright 2018 New Vector Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import abc
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import logging
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import re
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from six import raise_from
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from six.moves import urllib
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from twisted.internet import defer
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import synapse.logging.opentracing as opentracing
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from synapse.api.errors import (
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CodeMessageException,
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HttpResponseException,
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RequestSendFailed,
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SynapseError,
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)
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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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logger = logging.getLogger(__name__)
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class ReplicationEndpoint(object):
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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 an `/:txn_id` prefix 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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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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__metaclass__ = abc.ABCMeta
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NAME = abc.abstractproperty()
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PATH_ARGS = abc.abstractproperty()
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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):
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if self.CACHE:
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self.response_cache = ResponseCache(
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hs, "repl." + self.NAME, timeout_ms=30 * 60 * 1000
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)
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assert self.METHOD in ("PUT", "POST", "GET")
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@abc.abstractmethod
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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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Deferred[dict]|dict: If POST/PUT request then dictionary must be
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JSON serialisable, otherwise must be appropriate for adding as
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query args.
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"""
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return {}
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@abc.abstractmethod
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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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Deferred[dict]: A JSON serialisable dict to be used as response
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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 `_serialize_payload`.
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"""
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clock = hs.get_clock()
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host = hs.config.worker_replication_host
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port = hs.config.worker_replication_http_port
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client = hs.get_simple_http_client()
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@defer.inlineCallbacks
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def send_request(**kwargs):
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data = yield 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 = {}
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opentracing.inject_active_span_byte_dict(
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headers, None, check_destination=False
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)
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try:
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result = yield request_func(uri, data, headers=headers)
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break
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except CodeMessageException as e:
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if e.code != 504 or not cls.RETRY_ON_TIMEOUT:
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raise
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logger.warn("%s request timed out", 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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yield 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 master process that we should send to the client. (And
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# importantly, not stack traces everywhere)
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raise e.to_synapse_error()
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except RequestSendFailed as e:
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raise_from(SynapseError(502, "Failed to talk to master"), e)
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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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handler = self._handle_request
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method = self.METHOD
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if self.CACHE:
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handler = self._cached_handler
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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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opentracing.trace_servlet(self.__class__.__name__, extract_context=True)(
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handler
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),
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self.__class__.__name__,
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)
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def _cached_handler(self, request, txn_id, **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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assert self.CACHE
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return self.response_cache.wrap(txn_id, self._handle_request, request, **kwargs)
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