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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, self.__class__.__name__)
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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