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synapse/synmark/suites/logging.py
Eric Eastwood 5143f93dc9 Fix server_name in logging context for multiple Synapse instances in one process (#18868)
### Background

As part of Element's plan to support a light form of vhosting (virtual
host) (multiple instances of Synapse in the same Python process), we're
currently diving into the details and implications of running multiple
instances of Synapse in the same Python process.

"Per-tenant logging" tracked internally by
https://github.com/element-hq/synapse-small-hosts/issues/48

### Prior art

Previously, we exposed `server_name` by providing a static logging
`MetadataFilter` that injected the values:


205d9e4fc4/synapse/config/logger.py (L216)

While this can work fine for the normal case of one Synapse instance per
Python process, this configures things globally and isn't compatible
when we try to start multiple Synapse instances because each subsequent
tenant will overwrite the previous tenant.


### What does this PR do?

We remove the `MetadataFilter` and replace it by tracking the
`server_name` in the `LoggingContext` and expose it with our existing
[`LoggingContextFilter`](205d9e4fc4/synapse/logging/context.py (L584-L622))
that we already use to expose information about the `request`.

This means that the `server_name` value follows wherever we log as
expected even when we have multiple Synapse instances running in the
same process.


### A note on logcontext

Anywhere, Synapse mistakenly uses the `sentinel` logcontext to log
something, we won't know which server sent the log. We've been fixing up
`sentinel` logcontext usage as tracked by
https://github.com/element-hq/synapse/issues/18905

Any further `sentinel` logcontext usage we find in the future can be
fixed piecemeal as normal.


d2a966f922/docs/log_contexts.md (L71-L81)


### Testing strategy

1. Adjust your logging config to include `%(server_name)s` in the format
    ```yaml
    formatters:
        precise:
format: '%(asctime)s - %(server_name)s - %(name)s - %(lineno)d -
%(levelname)s - %(request)s - %(message)s'
    ```
1. Start Synapse: `poetry run synapse_homeserver --config-path
homeserver.yaml`
1. Make some requests (`curl
http://localhost:8008/_matrix/client/versions`, etc)
1. Open the homeserver logs and notice the `server_name` in the logs as
expected. `unknown_server_from_sentinel_context` is expected for the
`sentinel` logcontext (things outside of Synapse).
2025-09-26 17:10:48 -05:00

153 lines
4.4 KiB
Python

#
# This file is licensed under the Affero General Public License (AGPL) version 3.
#
# Copyright 2019 The Matrix.org Foundation C.I.C.
# Copyright (C) 2023 New Vector, Ltd
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.
#
# See the GNU Affero General Public License for more details:
# <https://www.gnu.org/licenses/agpl-3.0.html>.
#
# Originally licensed under the Apache License, Version 2.0:
# <http://www.apache.org/licenses/LICENSE-2.0>.
#
# [This file includes modifications made by New Vector Limited]
#
#
import logging
import logging.config
import warnings
from io import StringIO
from typing import Optional
from unittest.mock import Mock
from pyperf import perf_counter
from twisted.internet.address import IPv4Address, IPv6Address
from twisted.internet.defer import Deferred
from twisted.internet.protocol import ServerFactory
from twisted.logger import LogBeginner, LogPublisher
from twisted.protocols.basic import LineOnlyReceiver
from synapse.config.logger import _setup_stdlib_logging
from synapse.logging import RemoteHandler
from synapse.synapse_rust import reset_logging_config
from synapse.types import ISynapseReactor
from synapse.util.clock import Clock
class LineCounter(LineOnlyReceiver):
delimiter = b"\n"
count = 0
def lineReceived(self, line: bytes) -> None:
self.count += 1
assert isinstance(self.factory, Factory)
if self.count >= self.factory.wait_for and self.factory.on_done:
on_done = self.factory.on_done
self.factory.on_done = None
on_done.callback(True)
class Factory(ServerFactory):
protocol = LineCounter
wait_for: int
on_done: Optional[Deferred]
async def main(reactor: ISynapseReactor, loops: int) -> float:
"""
Benchmark how long it takes to send `loops` messages.
"""
logger_factory = Factory()
logger_factory.wait_for = loops
logger_factory.on_done = Deferred()
port = reactor.listenTCP(0, logger_factory, backlog=50, interface="127.0.0.1")
# A fake homeserver config.
class Config:
class server:
server_name = "synmark-" + str(loops)
# This odd construct is to avoid mypy thinking that logging escapes the
# scope of Config.
class _logging:
no_redirect_stdio = True
logging = _logging
hs_config = Config()
# To be able to sleep.
clock = Clock(reactor, server_name=hs_config.server.server_name)
errors = StringIO()
publisher = LogPublisher()
mock_sys = Mock()
beginner = LogBeginner(
publisher, errors, mock_sys, warnings, initialBufferSize=loops
)
address = port.getHost()
assert isinstance(address, (IPv4Address, IPv6Address))
log_config = {
"version": 1,
"loggers": {"synapse": {"level": "DEBUG", "handlers": ["remote"]}},
"formatters": {"tersejson": {"class": "synapse.logging.TerseJsonFormatter"}},
"handlers": {
"remote": {
"class": "synapse.logging.RemoteHandler",
"formatter": "tersejson",
"host": address.host,
"port": address.port,
"maximum_buffer": 100,
}
},
}
logger = logging.getLogger("synapse")
_setup_stdlib_logging(
hs_config, # type: ignore[arg-type]
None,
logBeginner=beginner,
)
# Force a new logging config without having to load it from a file.
logging.config.dictConfig(log_config)
reset_logging_config()
# Wait for it to connect...
for handler in logging.getLogger("synapse").handlers:
if isinstance(handler, RemoteHandler):
break
else:
raise RuntimeError("Improperly configured: no RemoteHandler found.")
await handler._service.whenConnected(failAfterFailures=10)
start = perf_counter()
# Send a bunch of useful messages
for i in range(loops):
logger.info("test message %s", i)
if len(handler._buffer) == handler.maximum_buffer:
while len(handler._buffer) > handler.maximum_buffer / 2:
await clock.sleep(0.01)
await logger_factory.on_done
end = perf_counter() - start
handler.close()
port.stopListening()
return end