Add colored HTTP/WebSocket access logging to fastapi_vue.server.

run() gains access_log (default on) and log_config parameters.  When
enabled, uvicorn's own access log is disabled (access_log=False) and
replaced by an ASGI middleware (adapted from the uvicorn access-log
branch) that logs colored request lines, WebSocket open/close pairs,
and pre-accept rejections in open format.

log_config dicts (uvicorn's default or user-supplied) are patched
best-effort via a registered patch pipeline in fastapi_vue.logging:
swapping in our AccessFormatter, routing our output to a private
fastapi_vue.access logger (uvicorn gates its protocol-level access
logging on uvicorn.access.hasHandlers(), so that logger must stay
handlerless), and filtering stock WebSocket handshake chatter from
uvicorn.error.  Non-dict or structurally unexpected configs pass
through untouched.

The middleware is installed by patching Config.load/load_app, hooked
into AccessFormatter instantiation so reload/worker subprocesses
(which re-apply log_config without re-calling run()) are covered.
This commit is contained in:
2026-08-31 04:16:43 +00:00
parent 52ca3f4f49
commit 77a34753d9
3 changed files with 602 additions and 1 deletions
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"""Access log formatting, adapted from uvicorn's logging module.
Unlike uvicorn's AccessFormatter, the colored fields (``client``, ``status``,
``method``, ``host``, ``path``, ``extra``, ``timing``) are supplied by the
access log middleware via ``extra=``. When colors are disabled the ANSI
escape codes are stripped from the assembled output so the same formatting
code path produces plain text.
"""
from __future__ import annotations
import logging
import re
import sys
from collections.abc import Callable
from contextlib import suppress
from copy import deepcopy
from typing import Any, Literal
ANSI_ESCAPE_RE = re.compile(r"\x1b\[[0-9;]*m")
ACCESS_LOG_FMT = "%(client)s %(status)s %(method)s %(host)s%(path)s %(extra)s%(timing)s"
def strip_ansi(text: str) -> str:
return ANSI_ESCAPE_RE.sub("", text)
LogConfigPatch = Callable[[dict[str, Any]], None]
_LOG_CONFIG_PATCHES: list[LogConfigPatch] = []
def log_config_patch(patch: LogConfigPatch) -> LogConfigPatch:
"""Register a best-effort log config patch (applied by patch_log_config)."""
_LOG_CONFIG_PATCHES.append(patch)
return patch
def patch_log_config(log_config: Any) -> Any: # noqa: ANN401
"""Apply registered patches to a uvicorn log_config.
Users presumably base their config on uvicorn's default dict, but any
shape is tolerated: each patch is applied on a best-effort basis and
silently skipped when the config does not have the expected structure.
Non-dict configs (e.g. an ini file path) pass through untouched.
"""
if not isinstance(log_config, dict):
return log_config
config = deepcopy(log_config)
for patch in _LOG_CONFIG_PATCHES:
with suppress(Exception):
patch(config)
return config
class WebSocketChatterFilter(logging.Filter):
"""Drop stock uvicorn WebSocket handshake/chatter records.
Stock uvicorn logs WS handshakes (``'%s - "WebSocket %s" ...'``) and the
websockets library's "connection open/closed" chatter to ``uvicorn.error``,
ungated by ``access_log``. Our middleware logs WebSockets itself.
"""
_PREFIXES = ('%s - "WebSocket ', "connection open", "connection closed", "connection rejected")
def filter(self, record: logging.LogRecord) -> bool:
msg = record.msg
if not isinstance(msg, str):
return True
return not msg.startswith(self._PREFIXES)
class AccessFormatter(logging.Formatter):
"""Formatter for the combined HTTP/WebSocket access log.
Instantiation installs the middleware patch: ``dictConfig`` builds this
formatter while uvicorn applies ``log_config``, which happens before the
app is loaded — including in reload/worker subprocesses that re-import the
config without calling ``fastapi_vue.server.run()`` again.
"""
def __init__(
self,
fmt: str | None = None,
datefmt: str | None = None,
style: Literal["%", "{", "$"] = "%",
use_colors: bool | None = None,
):
install_access_log()
if use_colors in (True, False):
self.use_colors = use_colors
else:
self.use_colors = sys.stdout.isatty()
super().__init__(fmt=fmt, datefmt=datefmt, style=style)
def formatMessage(self, record: logging.LogRecord) -> str:
formatted = super().formatMessage(record)
if not self.use_colors:
formatted = strip_ansi(formatted)
return formatted
def install_access_log() -> None:
"""Wrap apps loaded by uvicorn with AccessLogMiddleware (idempotent)."""
from uvicorn.config import Config
from .accesslog import AccessLogMiddleware
if getattr(Config, "_fastapi_vue_accesslog", False):
return
Config._fastapi_vue_accesslog = True # type: ignore[attr-defined]
if hasattr(Config, "load_app"): # uvicorn < 0.40
original_load_app = Config.load_app
def load_app(self): # noqa: ANN001, ANN202
app = original_load_app(self)
return app if isinstance(app, AccessLogMiddleware) else AccessLogMiddleware(app)
Config.load_app = load_app # type: ignore[method-assign]
else:
original_load = Config.load
def load(self): # noqa: ANN001, ANN202
original_load(self)
if not isinstance(self.loaded_app, AccessLogMiddleware):
self.loaded_app = AccessLogMiddleware(self.loaded_app)
Config.load = load # type: ignore[method-assign]
@log_config_patch
def _patch_access_log(config: dict[str, Any]) -> None:
"""Rewire a uvicorn log_config dict for our colored access logging.
Logs to a private ``fastapi_vue.access`` logger: uvicorn's protocol-level
access logging is driven by ``uvicorn.access.hasHandlers()``, so we must
not attach handlers to that logger (``access_log=False`` strips them).
"""
formatters = config.get("formatters")
if isinstance(formatters, dict):
formatters["access"] = {
"()": "fastapi_vue.logging.AccessFormatter",
"fmt": ACCESS_LOG_FMT,
"use_colors": None,
}
handlers = config.get("handlers")
if not isinstance(handlers, dict):
return
loggers = config.setdefault("loggers", {})
if isinstance(loggers, dict) and "access" in handlers:
loggers["fastapi_vue.access"] = {
"handlers": ["access"],
"level": "INFO",
"propagate": False,
}
default = handlers.get("default")
if isinstance(default, dict):
filters = config.setdefault("filters", {})
if isinstance(filters, dict):
filters["ws_chatter"] = {"()": "fastapi_vue.logging.WebSocketChatterFilter"}
handler_filters = default.setdefault("filters", [])
if isinstance(handler_filters, list) and "ws_chatter" not in handler_filters:
handler_filters.append("ws_chatter")