forked-synapse/synapse/replication/http/_base.py
Erik Johnston 8f35f8148e
Fix bug where a new writer advances their token too quickly (#16473)
* Fix bug where a new writer advances their token too quickly

When starting a new writer (for e.g. persisting events), the
`MultiWriterIdGenerator` doesn't have a minimum token for it as there
are no rows matching that new writer in the DB.

This results in the the first stream ID it acquired being announced as
persisted *before* it actually finishes persisting, if another writer
gets and persists a subsequent stream ID. This is due to the logic of
setting the minimum persisted position to the minimum known position of
across all writers, and the new writer starts off not being considered.

* Fix sending out POSITIONs when our token advances without update

Broke in #14820

* For replication HTTP requests, only wait for minimal position
2023-10-23 16:57:30 +01:00

441 lines
18 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, ClassVar, 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.config.workers import MAIN_PROCESS_INSTANCE_NAME
from synapse.http import RequestTimedOutError
from synapse.http.server import HttpServer
from synapse.http.servlet import parse_json_object_from_request
from synapse.http.site import SynapseRequest
from synapse.logging import opentracing
from synapse.logging.opentracing import trace_with_opname
from synapse.types import JsonDict
from synapse.util.caches.response_cache import ResponseCache
from synapse.util.cancellation import is_function_cancellable
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"],
)
_STREAM_POSITION_KEY = "_INT_STREAM_POS"
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.
WAIT_FOR_STREAMS (bool): Whether to wait for replication streams to
catch up before processing the request and/or response. Defaults to
True.
"""
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)
WAIT_FOR_STREAMS: ClassVar[bool] = True
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
self._streams = hs.get_replication_command_handler().get_streams_to_replicate()
self._replication = hs.get_replication_data_handler()
self._instance_name = hs.get_instance_name()
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:
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, content: JsonDict, **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_replication_client()
local_instance_name = hs.get_instance_name()
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_with_opname("outgoing_replication_request")
async def send_request(
*, instance_name: str = MAIN_PROCESS_INSTANCE_NAME, **kwargs: Any
) -> Any:
# We have to pull these out here to avoid circular dependencies...
streams = hs.get_replication_command_handler().get_streams_to_replicate()
replication = hs.get_replication_data_handler()
with outgoing_gauge.track_inprogress():
if instance_name == local_instance_name:
raise Exception("Trying to send HTTP request to self")
if instance_name not in instance_map:
raise Exception(
"Instance %r not in 'instance_map' config" % (instance_name,)
)
data = await cls._serialize_payload(**kwargs)
if cls.METHOD != "GET" and cls.WAIT_FOR_STREAMS:
# Include the current stream positions that we write to. We
# don't do this for GETs as they don't have a body, and we
# generally assume that a GET won't rely on data we have
# written.
if _STREAM_POSITION_KEY in data:
raise Exception(
"data to send contains %r key", _STREAM_POSITION_KEY
)
data[_STREAM_POSITION_KEY] = {
"streams": {
stream.NAME: stream.minimal_local_current_token()
for stream in streams
},
"instance_name": local_instance_name,
}
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,)
)
# Hard code a special scheme to show this only used for replication. The
# instance_name will be passed into the ReplicationEndpointFactory to
# determine connection details from the instance_map.
uri = "synapse-replication://%s/_synapse/replication/%s/%s" % (
instance_name,
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()
# Wait on any streams that the remote may have written to.
for stream_name, position in result.pop(
_STREAM_POSITION_KEY, {}
).items():
await replication.wait_for_stream_position(
instance_name=instance_name,
stream_name=stream_name,
position=position,
)
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_function_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.METHOD == "GET":
# GET APIs always have an empty body.
content = {}
else:
content = parse_json_object_from_request(request)
# Wait on any streams that the remote may have written to.
for stream_name, position in content.get(_STREAM_POSITION_KEY, {"streams": {}})[
"streams"
].items():
await self._replication.wait_for_stream_position(
instance_name=content[_STREAM_POSITION_KEY]["instance_name"],
stream_name=stream_name,
position=position,
)
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.
code, response = await self.response_cache.wrap(
txn_id, self._handle_request, request, content, **kwargs
)
# Take a copy so we don't mutate things in the cache.
response = dict(response)
else:
# 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_function_cancellable(
self._handle_request
)
code, response = await self._handle_request(request, content, **kwargs)
# Return streams we may have written to in the course of processing this
# request.
if _STREAM_POSITION_KEY in response:
raise Exception("data to send contains %r key", _STREAM_POSITION_KEY)
if self.WAIT_FOR_STREAMS:
response[_STREAM_POSITION_KEY] = {
stream.NAME: stream.current_token(self._instance_name)
for stream in self._streams
}
return code, response