一、背景

有人提出，message日志不能放我們自己的服務的日志，需要將該日志單獨搞到一個地方。

二、先說結論

本文直接上結論，可能是全CSDN唯一的解釋。哈哈哈哈哈哈哈哈。

在uvicorn啟動的時候，傳入log_config參數

那么，這個參數如何傳呢？我先給個樣例

LOGGING_CONFIG = {"version": 1,"disable_existing_loggers": False,"formatters": {"default": {"()": "uvicorn.logging.DefaultFormatter","fmt": "%(levelprefix)s %(message)s","use_colors": None,},"access": {"()": "uvicorn.logging.AccessFormatter","fmt": '%(levelprefix)s %(client_addr)s - "%(request_line)s" %(status_code)s',},},"handlers": {"default": {"formatter": "default","class": "logging.handlers.TimedRotatingFileHandler","filename": "./log"},"access": {"formatter": "access","class": "logging.handlers.TimedRotatingFileHandler","filename": "./log"},},"loggers": {"": {"handlers": ["default"], "level": "INFO"},"uvicorn.error": {"level": "INFO"},"uvicorn.access": {"handlers": ["access"], "level": "INFO", "propagate": False},}, }

這樣的配置，會使unicorn 的日志，按照TimedRotatingFileHandler的默認切割方法，將日志寫到我們配置的./log文件中

三、源碼解析

首先，我們先在一個代碼文件中，將服務跑起來，用官網的命令行方式也是一樣，這里不過多介紹

from typing import Optionalimport uvicorn from fastapi import FastAPIapp = FastAPI()@app.get("/") def read_root():return {"Hello": "World"}@app.get("/items/{item_id}") def read_item(item_id: int, q: Optional[str] = None):return {"item_id": item_id, "q": q}if __name__ == "__main__":uvicorn.run(app=app,host="0.0.0.0",port=12345,)

運行結果如下：

遇到了問題，先去看了看官方文檔。

但官方文檔，就這么一點點，只說有個參數能配置，十分令人生氣。（迅速調整情緒）開始讀源碼。

點住 run 方法，進去看看

再點開Config進去看看

原來，這里給了一個默認的日志配置，再往下點 LOGGING_CONFIG

就找到了默認的配置：

LOGGING_CONFIG = {"version": 1,"disable_existing_loggers": False,"formatters": {"default": {"()": "uvicorn.logging.DefaultFormatter","fmt": "%(levelprefix)s %(message)s","use_colors": None,},"access": {"()": "uvicorn.logging.AccessFormatter","fmt": '%(levelprefix)s %(client_addr)s - "%(request_line)s" %(status_code)s',},},"handlers": {"default": {"formatter": "default","class": "logging.StreamHandler","stream": "ext://sys.stderr",},"access": {"formatter": "access","class": "logging.StreamHandler","stream": "ext://sys.stdout",},},"loggers": {"": {"handlers": ["default"], "level": "INFO"},"uvicorn.error": {"level": "INFO"},"uvicorn.access": {"handlers": ["access"], "level": "INFO", "propagate": False},}, }

再繼續往下追，看看這個 配置使如何處理的呢

來到233行，對字典的配置的處理，繼續往下點，來到了關鍵的代碼：這一塊對字典中的內容進行解析。

?

?

?來到了

self.configure_logger(name, loggers[name])——————————————再往里面進入，點一層

?來看這個函數，我們就看到了本質，本質上，還是給logger.addHandler方法。

def common_logger_config(self, logger, config, incremental=False):"""Perform configuration which is common to root and non-root loggers."""level = config.get('level', None)if level is not None:logger.setLevel(logging._checkLevel(level))if not incremental:#Remove any existing handlersfor h in logger.handlers[:]:logger.removeHandler(h)handlers = config.get('handlers', None)if handlers:self.add_handlers(logger, handlers)filters = config.get('filters', None)if filters:self.add_filters(logger, filters)def add_handlers(self, logger, handlers):"""Add handlers to a logger from a list of names."""for h in handlers:try:logger.addHandler(self.config['handlers'][h])except Exception as e:raise ValueError('Unable to add handler %r' % h) from e

這段代碼追到這里就可以停止了。回頭追解析部分。

for name in sorted(handlers):try:handler = self.configure_handler(handlers[name])

?話不多說，直接把函數貼上來了。

def configure_handler(self, config):"""Configure a handler from a dictionary."""config_copy = dict(config) # for restoring in case of errorformatter = config.pop('formatter', None)if formatter:try:formatter = self.config['formatters'][formatter]except Exception as e:raise ValueError('Unable to set formatter ''%r' % formatter) from elevel = config.pop('level', None)filters = config.pop('filters', None)if '()' in config:c = config.pop('()')if not callable(c):c = self.resolve(c)factory = celse:cname = config.pop('class')klass = self.resolve(cname)#Special case for handler which refers to another handlerif issubclass(klass, logging.handlers.MemoryHandler) and\'target' in config:try:th = self.config['handlers'][config['target']]if not isinstance(th, logging.Handler):config.update(config_copy) # restore for deferred cfgraise TypeError('target not configured yet')config['target'] = thexcept Exception as e:raise ValueError('Unable to set target handler ''%r' % config['target']) from eelif issubclass(klass, logging.handlers.SMTPHandler) and\'mailhost' in config:config['mailhost'] = self.as_tuple(config['mailhost'])elif issubclass(klass, logging.handlers.SysLogHandler) and\'address' in config:config['address'] = self.as_tuple(config['address'])factory = klassprops = config.pop('.', None)kwargs = {k: config[k] for k in config if valid_ident(k)}try:result = factory(**kwargs)except TypeError as te:if "'stream'" not in str(te):raise#The argument name changed from strm to stream#Retry with old name.#This is so that code can be used with older Python versions#(e.g. by Django)kwargs['strm'] = kwargs.pop('stream')result = factory(**kwargs)if formatter:result.setFormatter(formatter)if level is not None:result.setLevel(logging._checkLevel(level))if filters:self.add_filters(result, filters)if props:for name, value in props.items():setattr(result, name, value)return result

請注意以下兩行
?

klass = self.resolve(cname) factory = klass result = factory(**kwargs)

再結合resolve方法，發現，這就是個通過類名獲取該類的方法。然后再把參數傳給該類。

我理解，就是JAVA中的反射機制

源碼就看到這里了。

四、實戰解析

1.首先找到我們想要配置的Handler

可以參考我之前的文章

Python日志詳解【兩篇就夠了系列】--第一篇logging_康雨城的博客-CSDN博客

2.修改已有配置為自己的配置

?

?不難發現，class為類名，后面的參數就是類的參數名。

五、啟動驗證

from typing import Optionalimport uvicorn from fastapi import FastAPIapp = FastAPI()@app.get("/") def read_root():return {"Hello": "World"}@app.get("/items/{item_id}") def read_item(item_id: int, q: Optional[str] = None):return {"item_id": item_id, "q": q}LOGGING_CONFIG = {"version": 1,"disable_existing_loggers": False,"formatters": {"default": {"()": "uvicorn.logging.DefaultFormatter","fmt": "%(levelprefix)s %(message)s","use_colors": None,},"access": {"()": "uvicorn.logging.AccessFormatter","fmt": '%(levelprefix)s %(client_addr)s - "%(request_line)s" %(status_code)s',},},"handlers": {"default": {"formatter": "default","class": "logging.handlers.TimedRotatingFileHandler","filename": "./log"},"access": {"formatter": "access","class": "logging.handlers.TimedRotatingFileHandler","filename": "./log"},},"loggers": {"": {"handlers": ["default"], "level": "INFO"},"uvicorn.error": {"level": "INFO"},"uvicorn.access": {"handlers": ["access"], "level": "INFO", "propagate": False},}, }if __name__ == "__main__":uvicorn.run(app=app,host="0.0.0.0",port=12345,log_config=LOGGING_CONFIG,)

可以發現，日志打到了文件里面

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