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- # -*- coding: utf-8 -*-
- # 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
- from six import raise_from
- from six.moves import urllib
- from twisted.internet import defer
- from synapse.api.errors import (
- CodeMessageException,
- HttpResponseException,
- RequestSendFailed,
- SynapseError,
- )
- from synapse.util.caches.response_cache import ResponseCache
- from synapse.util.stringutils import random_string
- logger = logging.getLogger(__name__)
- class ReplicationEndpoint(object):
- """Helper base class for defining new replication HTTP endpoints.
- This creates an endpoint under `/_synapse/replication/:NAME/:PATH_ARGS..`
- (with an `/:txn_id` prefix 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`.
- 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.
- """
- __metaclass__ = abc.ABCMeta
- NAME = abc.abstractproperty()
- PATH_ARGS = abc.abstractproperty()
- METHOD = "POST"
- CACHE = True
- RETRY_ON_TIMEOUT = True
- def __init__(self, hs):
- if self.CACHE:
- self.response_cache = ResponseCache(
- hs, "repl." + self.NAME, timeout_ms=30 * 60 * 1000
- )
- assert self.METHOD in ("PUT", "POST", "GET")
- @abc.abstractmethod
- def _serialize_payload(**kwargs):
- """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:
- Deferred[dict]|dict: If POST/PUT request then dictionary must be
- JSON serialisable, otherwise must be appropriate for adding as
- query args.
- """
- return {}
- @abc.abstractmethod
- def _handle_request(self, request, **kwargs):
- """Handle incoming request.
- This is called with the request object and PATH_ARGS.
- Returns:
- Deferred[dict]: A JSON serialisable dict to be used as response
- body of request.
- """
- pass
- @classmethod
- def make_client(cls, hs):
- """Create a client that makes requests.
- Returns a callable that accepts the same parameters as `_serialize_payload`.
- """
- clock = hs.get_clock()
- host = hs.config.worker_replication_host
- port = hs.config.worker_replication_http_port
- client = hs.get_simple_http_client()
- @defer.inlineCallbacks
- def send_request(**kwargs):
- data = yield 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 = 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,)
- )
- uri = "http://%s:%s/_synapse/replication/%s/%s" % (
- host,
- port,
- cls.NAME,
- "/".join(url_args),
- )
- try:
- # 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 = yield request_func(uri, data)
- break
- except CodeMessageException as e:
- if e.code != 504 or not cls.RETRY_ON_TIMEOUT:
- raise
- logger.warn("%s request timed out", 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.
- yield clock.sleep(1)
- except HttpResponseException as e:
- # We convert to SynapseError as we know that it was a SynapseError
- # on the master process that we should send to the client. (And
- # importantly, not stack traces everywhere)
- raise e.to_synapse_error()
- except RequestSendFailed as e:
- raise_from(SynapseError(502, "Failed to talk to master"), e)
- return result
- return send_request
- def register(self, http_server):
- """Called by the server to register this as a handler to the
- appropriate path.
- """
- url_args = list(self.PATH_ARGS)
- handler = self._handle_request
- method = self.METHOD
- if self.CACHE:
- handler = self._cached_handler
- 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], handler)
- def _cached_handler(self, request, txn_id, **kwargs):
- """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.
- assert self.CACHE
- return self.response_cache.wrap(txn_id, self._handle_request, request, **kwargs)
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