# ? 反面教材：到處散落的 print
def process_order(order_id):
    print(f"開始處理訂單: {order_id}")
    print("查詢數(shù)據(jù)庫(kù)...")
    print("訂單處理完成")

# logger_setup.py —— 基礎(chǔ)版日志配置
import logging
import sys
from pathlib import Path

def create_logger(name: str, log_file: str = None, level: int = logging.DEBUG) -> logging.Logger:
    """
    創(chuàng)建一個(gè)既輸出到控制臺(tái)又寫入文件的 Logger
    """
    logger = logging.getLogger(name)
    logger.setLevel(level)

    # 避免重復(fù)添加 Handler（多次調(diào)用時(shí)的常見坑）
    if logger.handlers:
        return logger

    # 格式化器：包含時(shí)間、級(jí)別、模塊、行號(hào)
    formatter = logging.Formatter(
        fmt="%(asctime)s | %(levelname)-8s | %(name)s:%(lineno)d | %(message)s",
        datefmt="%Y-%m-%d %H:%M:%S"
    )

    # 控制臺(tái) Handler
    console_handler = logging.StreamHandler(sys.stdout)
    console_handler.setLevel(logging.INFO)
    console_handler.setFormatter(formatter)
    logger.addHandler(console_handler)

    # 文件 Handler（可選）
    if log_file:
        Path(log_file).parent.mkdir(parents=True, exist_ok=True)
        file_handler = logging.FileHandler(log_file, encoding="utf-8")
        file_handler.setLevel(logging.DEBUG)
        file_handler.setFormatter(formatter)
        logger.addHandler(file_handler)

    return logger


# 使用示例
logger = create_logger("myapp", log_file="logs/app.log")
logger.info("服務(wù)啟動(dòng)成功")
logger.debug("當(dāng)前配置: host=localhost, port=8080")
logger.error("數(shù)據(jù)庫(kù)連接失敗")

# json_logger.py —— JSON 結(jié)構(gòu)化日志
import json
import logging
import traceback
from datetime import datetime, timezone

class JSONFormatter(logging.Formatter):
    """
    將日志格式化為 JSON，便于日志系統(tǒng)解析
    """
    def __init__(self, service_name: str = "app", env: str = "production"):
        super().__init__()
        self.service_name = service_name
        self.env = env

    def format(self, record: logging.LogRecord) -> str:
        log_data = {
            "timestamp": datetime.now(timezone.utc).isoformat(),
            "level": record.levelname,
            "logger": record.name,
            "message": record.getMessage(),
            "module": record.module,
            "function": record.funcName,
            "line": record.lineno,
            "service": self.service_name,
            "env": self.env,
        }

        # 附加異常信息
        if record.exc_info:
            log_data["exception"] = {
                "type": record.exc_info[0].__name__,
                "message": str(record.exc_info[1]),
                "traceback": traceback.format_exception(*record.exc_info)
            }

        # 支持額外的上下文字段（通過 extra 參數(shù)傳入）
        if hasattr(record, "extra_fields"):
            log_data.update(record.extra_fields)

        return json.dumps(log_data, ensure_ascii=False)


# 配置 JSON Logger
def get_json_logger(name: str) -> logging.Logger:
    logger = logging.getLogger(name)
    logger.setLevel(logging.DEBUG)

    if not logger.handlers:
        handler = logging.StreamHandler()
        handler.setFormatter(JSONFormatter(service_name="order-service", env="prod"))
        logger.addHandler(handler)

    return logger


# 實(shí)際使用
logger = get_json_logger("order_service")
logger.info("訂單創(chuàng)建成功", extra={"extra_fields": {"order_id": "ORD-12345", "user_id": "U-001", "amount": 299.9}})

{
  "timestamp": "2024-03-15T06:32:01.123456+00:00",
  "level": "INFO",
  "logger": "order_service",
  "message": "訂單創(chuàng)建成功",
  "module": "app",
  "function": "create_order",
  "line": 42,
  "service": "order-service",
  "env": "prod",
  "order_id": "ORD-12345",
  "user_id": "U-001",
  "amount": 299.9
}

# context_logger.py —— 基于 contextvars 的請(qǐng)求追蹤
import logging
import uuid
from contextvars import ContextVar

# 存儲(chǔ)當(dāng)前請(qǐng)求的 trace_id（線程/協(xié)程安全）
_trace_id: ContextVar[str] = ContextVar("trace_id", default="N/A")


class TraceIDFilter(logging.Filter):
    """
    自動(dòng)將 trace_id 注入每條日志記錄
    """
    def filter(self, record: logging.LogRecord) -> bool:
        record.trace_id = _trace_id.get()
        return True


def set_trace_id(trace_id: str = None) -> str:
    """設(shè)置當(dāng)前上下文的 trace_id"""
    tid = trace_id or str(uuid.uuid4())[:8]
    _trace_id.set(tid)
    return tid


def get_trace_logger(name: str) -> logging.Logger:
    logger = logging.getLogger(name)
    logger.setLevel(logging.DEBUG)

    if not logger.handlers:
        handler = logging.StreamHandler()
        formatter = logging.Formatter(
            "%(asctime)s | %(levelname)-8s | [%(trace_id)s] | %(name)s | %(message)s",
            datefmt="%H:%M:%S"
        )
        handler.setFormatter(formatter)
        handler.addFilter(TraceIDFilter())
        logger.addHandler(handler)

    return logger


# 模擬 Web 請(qǐng)求處理
logger = get_trace_logger("web.handler")

def handle_request(request_data: dict):
    trace_id = set_trace_id()  # 每個(gè)請(qǐng)求生成唯一 ID
    logger.info(f"收到請(qǐng)求: {request_data.get('path')}")

    try:
        # 模擬業(yè)務(wù)處理
        process_business_logic(request_data)
        logger.info("請(qǐng)求處理完成")
    except Exception as e:
        logger.error(f"請(qǐng)求處理失敗: {e}", exc_info=True)

def process_business_logic(data: dict):
    logger.debug(f"開始執(zhí)行業(yè)務(wù)邏輯，參數(shù): {data}")
    # ... 業(yè)務(wù)代碼


handle_request({"path": "/api/orders", "method": "POST"})

# rotating_logger.py —— 生產(chǎn)環(huán)境日志輪轉(zhuǎn)配置
import logging
from logging.handlers import RotatingFileHandler, TimedRotatingFileHandler

def setup_production_logger(name: str) -> logging.Logger:
    logger = logging.getLogger(name)
    logger.setLevel(logging.DEBUG)

    formatter = logging.Formatter(
        "%(asctime)s | %(levelname)-8s | %(name)s:%(lineno)d | %(message)s"
    )

    # 按大小輪轉(zhuǎn)：?jiǎn)挝募畲?10MB，保留最近 5 個(gè)備份
    size_handler = RotatingFileHandler(
        filename="logs/app.log",
        maxBytes=10 * 1024 * 1024,  # 10MB
        backupCount=5,
        encoding="utf-8"
    )
    size_handler.setLevel(logging.INFO)
    size_handler.setFormatter(formatter)

    # 按時(shí)間輪轉(zhuǎn)：每天午夜切割，保留 30 天
    time_handler = TimedRotatingFileHandler(
        filename="logs/app_daily.log",
        when="midnight",
        interval=1,
        backupCount=30,
        encoding="utf-8"
    )
    time_handler.setLevel(logging.DEBUG)
    time_handler.setFormatter(formatter)

    # 錯(cuò)誤日志單獨(dú)存放，便于告警
    error_handler = RotatingFileHandler(
        filename="logs/error.log",
        maxBytes=5 * 1024 * 1024,
        backupCount=10,
        encoding="utf-8"
    )
    error_handler.setLevel(logging.ERROR)
    error_handler.setFormatter(formatter)

    logger.addHandler(size_handler)
    logger.addHandler(time_handler)
    logger.addHandler(error_handler)

    return logger

# main.py —— FastAPI 應(yīng)用完整日志方案
import logging
import time
import uuid
from contextlib import asynccontextmanager
from contextvars import ContextVar

from fastapi import FastAPI, Request, Response

# ─── 日志初始化 ────────────────────────────────
_request_id: ContextVar[str] = ContextVar("request_id", default="-")

class RequestIDFilter(logging.Filter):
    def filter(self, record):
        record.request_id = _request_id.get()
        return True

def init_logging():
    root_logger = logging.getLogger()
    root_logger.setLevel(logging.DEBUG)

    handler = logging.StreamHandler()
    handler.setFormatter(logging.Formatter(
        "%(asctime)s | %(levelname)-8s | [%(request_id)s] | %(name)s | %(message)s",
        datefmt="%Y-%m-%d %H:%M:%S"
    ))
    handler.addFilter(RequestIDFilter())
    root_logger.addHandler(handler)

init_logging()
logger = logging.getLogger("api")

# ─── FastAPI 應(yīng)用 ──────────────────────────────
app = FastAPI()

@app.middleware("http")
async def logging_middleware(request: Request, call_next) -> Response:
    """
    請(qǐng)求中間件：自動(dòng)注入 request_id，記錄請(qǐng)求耗時(shí)
    """
    request_id = request.headers.get("X-Request-ID") or str(uuid.uuid4())[:8]
    _request_id.set(request_id)

    start_time = time.perf_counter()
    logger.info(f"→ {request.method} {request.url.path}")

    response = await call_next(request)

    duration_ms = (time.perf_counter() - start_time) * 1000
    logger.info(
        f"← {request.method} {request.url.path} "
        f"status={response.status_code} duration={duration_ms:.1f}ms"
    )
    response.headers["X-Request-ID"] = request_id
    return response


@app.get("/orders/{order_id}")
async def get_order(order_id: str):
    logger.debug(f"查詢訂單詳情: order_id={order_id}")
    # 模擬數(shù)據(jù)庫(kù)查詢
    logger.info(f"訂單查詢成功: order_id={order_id}")
    return {"order_id": order_id, "status": "completed"}

2024-03-15 14:32:01 | INFO     | [4f8a1b2c] | api | → GET /orders/123
2024-03-15 14:32:01 | DEBUG    | [4f8a1b2c] | api | 查詢訂單詳情: order_id=123
2024-03-15 14:32:01 | INFO     | [4f8a1b2c] | api | 訂單查詢成功: order_id=123
2024-03-15 14:32:01 | INFO     | [4f8a1b2c] | api | ← GET /orders/123 status=200 duration=2.3ms

logger = logging.getLogger(__name__)  # 使用模塊名，自動(dòng)層級(jí)化

# ? 正確：logger 內(nèi)部處理，級(jí)別不夠時(shí)不拼接
logger.debug("處理用戶 %s 的請(qǐng)求", user_id)

# ? 錯(cuò)誤：無論級(jí)別是否達(dá)到，都會(huì)執(zhí)行字符串格式化
logger.debug(f"處理用戶 {user_id} 的請(qǐng)求")

try:
    risky_operation()
except Exception:
    logger.exception("操作失敗，完整堆棧如下：")  # 自動(dòng)附加 traceback

logger.info("支付完成", extra={"extra_fields": {
    "order_id": order.id,
    "amount": order.amount,
    "payment_method": order.payment_method,
    "duration_ms": elapsed
}})

# loguru 版本：5行代碼實(shí)現(xiàn)生產(chǎn)級(jí)日志
from loguru import logger

logger.remove()  # 移除默認(rèn) handler
logger.add("logs/app.log", rotation="10 MB", retention="30 days", 
           format="{time} | {level} | {name}:{line} | {message}",
           level="DEBUG", serialize=True)  # serialize=True 輸出 JSON
logger.add(sys.stdout, level="INFO", colorize=True)

logger.info("啟動(dòng)成功 ??")
logger.bind(user_id="U-001", order_id="ORD-123").info("綁定上下文的日志")