anonymousland-synapse/synapse/replication/http/_base.py
Sean Quah a559c8b0d9
Respect the @cancellable flag for ReplicationEndpoints (#12700)
While `ReplicationEndpoint`s register themselves via `JsonResource`,
they pass a method that calls the handler, instead of the handler itself,
to `register_paths`. As a result, `JsonResource` will not correctly pick
up the `@cancellable` flag and we have to apply it ourselves.

Signed-off-by: Sean Quah <seanq@element.io>
2022-05-11 12:25:39 +01:00

365 lines
15 KiB
Python

# 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
import urllib.parse
from inspect import signature
from typing import TYPE_CHECKING, Any, Awaitable, Callable, Dict, List, Tuple
from prometheus_client import Counter, Gauge
from twisted.internet.error import ConnectError, DNSLookupError
from twisted.web.server import Request
from synapse.api.errors import HttpResponseException, SynapseError
from synapse.http import RequestTimedOutError
from synapse.http.server import HttpServer, is_method_cancellable
from synapse.http.site import SynapseRequest
from synapse.logging import opentracing
from synapse.logging.opentracing import trace
from synapse.types import JsonDict
from synapse.util.caches.response_cache import ResponseCache
from synapse.util.stringutils import random_string
if TYPE_CHECKING:
from synapse.server import HomeServer
logger = logging.getLogger(__name__)
_pending_outgoing_requests = Gauge(
"synapse_pending_outgoing_replication_requests",
"Number of active outgoing replication requests, by replication method name",
["name"],
)
_outgoing_request_counter = Counter(
"synapse_outgoing_replication_requests",
"Number of outgoing replication requests, by replication method name and result",
["name", "code"],
)
class ReplicationEndpoint(metaclass=abc.ABCMeta):
"""Helper base class for defining new replication HTTP endpoints.
This creates an endpoint under `/_synapse/replication/:NAME/:PATH_ARGS..`
(with a `/:txn_id` suffix 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`.
Requests are sent to master process by default, but can be sent to other
named processes by specifying an `instance_name` keyword argument.
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.
RETRY_ON_CONNECT_ERROR (bool): Whether or not to retry the request when
a connection error is received.
RETRY_ON_CONNECT_ERROR_ATTEMPTS (int): Number of attempts to retry when
receiving connection errors, each will backoff exponentially longer.
"""
NAME: str = abc.abstractproperty() # type: ignore
PATH_ARGS: Tuple[str, ...] = abc.abstractproperty() # type: ignore
METHOD = "POST"
CACHE = True
RETRY_ON_TIMEOUT = True
RETRY_ON_CONNECT_ERROR = True
RETRY_ON_CONNECT_ERROR_ATTEMPTS = 5 # =63s (2^6-1)
def __init__(self, hs: "HomeServer"):
if self.CACHE:
self.response_cache: ResponseCache[str] = ResponseCache(
hs.get_clock(), "repl." + self.NAME, timeout_ms=30 * 60 * 1000
)
# We reserve `instance_name` as a parameter to sending requests, so we
# assert here that sub classes don't try and use the name.
assert (
"instance_name" not in self.PATH_ARGS
), "`instance_name` is a reserved parameter name"
assert (
"instance_name"
not in signature(self.__class__._serialize_payload).parameters
), "`instance_name` is a reserved parameter name"
assert self.METHOD in ("PUT", "POST", "GET")
self._replication_secret = None
if hs.config.worker.worker_replication_secret:
self._replication_secret = hs.config.worker.worker_replication_secret
def _check_auth(self, request: Request) -> None:
# Get the authorization header.
auth_headers = request.requestHeaders.getRawHeaders(b"Authorization")
if not auth_headers:
raise RuntimeError("Missing Authorization header.")
if len(auth_headers) > 1:
raise RuntimeError("Too many Authorization headers.")
parts = auth_headers[0].split(b" ")
if parts[0] == b"Bearer" and len(parts) == 2:
received_secret = parts[1].decode("ascii")
if self._replication_secret == received_secret:
# Success!
return
raise RuntimeError("Invalid Authorization header.")
@abc.abstractmethod
async def _serialize_payload(**kwargs) -> JsonDict:
"""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:
dict: If POST/PUT request then dictionary must be JSON serialisable,
otherwise must be appropriate for adding as query args.
"""
return {}
@abc.abstractmethod
async def _handle_request(
self, request: Request, **kwargs: Any
) -> Tuple[int, JsonDict]:
"""Handle incoming request.
This is called with the request object and PATH_ARGS.
Returns:
HTTP status code and a JSON serialisable dict to be used as response
body of request.
"""
@classmethod
def make_client(cls, hs: "HomeServer") -> Callable:
"""Create a client that makes requests.
Returns a callable that accepts the same parameters as
`_serialize_payload`, and also accepts an optional `instance_name`
parameter to specify which instance to hit (the instance must be in
the `instance_map` config).
"""
clock = hs.get_clock()
client = hs.get_simple_http_client()
local_instance_name = hs.get_instance_name()
master_host = hs.config.worker.worker_replication_host
master_port = hs.config.worker.worker_replication_http_port
instance_map = hs.config.worker.instance_map
outgoing_gauge = _pending_outgoing_requests.labels(cls.NAME)
replication_secret = None
if hs.config.worker.worker_replication_secret:
replication_secret = hs.config.worker.worker_replication_secret.encode(
"ascii"
)
@trace(opname="outgoing_replication_request")
async def send_request(*, instance_name: str = "master", **kwargs: Any) -> Any:
with outgoing_gauge.track_inprogress():
if instance_name == local_instance_name:
raise Exception("Trying to send HTTP request to self")
if instance_name == "master":
host = master_host
port = master_port
elif instance_name in instance_map:
host = instance_map[instance_name].host
port = instance_map[instance_name].port
else:
raise Exception(
"Instance %r not in 'instance_map' config" % (instance_name,)
)
data = await 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: Callable[
..., Awaitable[Any]
] = 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),
)
headers: Dict[bytes, List[bytes]] = {}
# Add an authorization header, if configured.
if replication_secret:
headers[b"Authorization"] = [b"Bearer " + replication_secret]
opentracing.inject_header_dict(headers, check_destination=False)
try:
# Keep track of attempts made so we can bail if we don't manage to
# connect to the target after N tries.
attempts = 0
# 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 = await request_func(uri, data, headers=headers)
break
except RequestTimedOutError:
if not cls.RETRY_ON_TIMEOUT:
raise
logger.warning("%s request timed out; retrying", 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.
await clock.sleep(1)
except (ConnectError, DNSLookupError) as e:
if not cls.RETRY_ON_CONNECT_ERROR:
raise
if attempts > cls.RETRY_ON_CONNECT_ERROR_ATTEMPTS:
raise
delay = 2**attempts
logger.warning(
"%s request connection failed; retrying in %ds: %r",
cls.NAME,
delay,
e,
)
await clock.sleep(delay)
attempts += 1
except HttpResponseException as e:
# We convert to SynapseError as we know that it was a SynapseError
# on the main process that we should send to the client. (And
# importantly, not stack traces everywhere)
_outgoing_request_counter.labels(cls.NAME, e.code).inc()
raise e.to_synapse_error()
except Exception as e:
_outgoing_request_counter.labels(cls.NAME, "ERR").inc()
raise SynapseError(
502, f"Failed to talk to {instance_name} process"
) from e
_outgoing_request_counter.labels(cls.NAME, 200).inc()
return result
return send_request
def register(self, http_server: HttpServer) -> None:
"""Called by the server to register this as a handler to the
appropriate path.
"""
url_args = list(self.PATH_ARGS)
method = self.METHOD
if self.CACHE and is_method_cancellable(self._handle_request):
raise Exception(
f"{self.__class__.__name__} has been marked as cancellable, but CACHE "
"is set. The cancellable flag would have no effect."
)
if self.CACHE:
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],
self._check_auth_and_handle,
self.__class__.__name__,
)
async def _check_auth_and_handle(
self, request: SynapseRequest, **kwargs: Any
) -> Tuple[int, JsonDict]:
"""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.
# Check the authorization headers before handling the request.
if self._replication_secret:
self._check_auth(request)
if self.CACHE:
txn_id = kwargs.pop("txn_id")
# We ignore the `@cancellable` flag, since cancellation wouldn't interupt
# `_handle_request` and `ResponseCache` does not handle cancellation
# correctly yet. In particular, there may be issues to do with logging
# context lifetimes.
return await self.response_cache.wrap(
txn_id, self._handle_request, request, **kwargs
)
# The `@cancellable` decorator may be applied to `_handle_request`. But we
# told `HttpServer.register_paths` that our handler is `_check_auth_and_handle`,
# so we have to set up the cancellable flag ourselves.
request.is_render_cancellable = is_method_cancellable(self._handle_request)
return await self._handle_request(request, **kwargs)