5分钟快速上手：用Python和SSE构建实时天气查询MCP服务（附OpenWeather配置）-优快云博客

Python与SSE构建实时天气服务的极简实践

1. 实时数据推送的技术选型

在现代Web应用中，实时数据推送已成为提升用户体验的关键技术。Server-Sent Events（SSE）作为一种轻量级的服务器到客户端单向通信协议，相比WebSocket和长轮询具有独特优势：

协议简洁性：基于标准HTTP协议，无需额外握手过程
自动重连：内置断线重连机制，客户端自动恢复连接
文本友好：原生支持UTF-8文本数据，适合消息类应用
资源消耗低：服务端维护成本远低于WebSocket

# SSE响应基本格式示例
def sse_response(data):
    return f"data: {json.dumps(data)}\n\n"

当我们需要构建一个实时天气查询服务时，SSE的简单性使其成为理想选择。以下是三种常见实时技术的对比：

特性	SSE	WebSocket	长轮询
通信方向	单向(服务端→客户端)	双向	半双工
协议复杂度	低	高	中
连接开销	低	中	高
断线处理	自动重连	需手动实现	每次请求重建
适合场景	实时通知	交互应用	兼容性要求高

2. 五分钟快速搭建SSE服务框架

2.1 基础环境配置

使用Python构建SSE服务无需复杂依赖，仅需标准库即可实现核心功能。推荐使用异步框架提升并发性能：

# 创建项目目录结构
mkdir weather-sse && cd weather-sse
python -m venv .venv
source .venv/bin/activate  # Linux/Mac
.venv\Scripts\activate     # Windows

# 安装推荐依赖
pip install httpx fastapi uvicorn

2.2 最小化SSE服务实现

以下代码展示了使用FastAPI构建的SSE端点核心逻辑：

from fastapi import FastAPI, Request
from fastapi.responses import StreamingResponse
import asyncio
import json

app = FastAPI()

async def weather_stream(request: Request):
    async def event_generator():
        while True:
            if await request.is_disconnected():
                break
            
            # 这里替换为实际的天气数据获取逻辑
            weather_data = {"temp": 25, "humidity": 60}
            
            yield f"data: {json.dumps(weather_data)}\n\n"
            await asyncio.sleep(10)  # 10秒更新间隔

    return StreamingResponse(
        event_generator(),
        media_type="text/event-stream",
        headers={"Cache-Control": "no-cache"}
    )

@app.get("/sse/weather")
async def weather_sse_endpoint(request: Request):
    return await weather_stream(request)

启动服务命令：

uvicorn main:app --reload --port 8000

3. OpenWeather API深度集成

3.1 API接入关键步骤

获取API密钥：
- 访问OpenWeather官网注册账户
- 在个人仪表板创建API Key
- 免费套餐支持每分钟60次请求

请求参数优化：

params = {
    "q": "Beijing,CN",
    "appid": "your_api_key",
    "units": "metric",  # 摄氏温度
    "lang": "zh_cn"     # 中文响应
}

错误处理机制：

async def fetch_weather(city: str):
    try:
        async with httpx.AsyncClient(timeout=10.0) as client:
            response = await client.get(API_URL, params=params)
            response.raise_for_status()
            return response.json()
    except httpx.HTTPStatusError as e:
        return {"error": f"API请求失败: {e.response.status_code}"}
    except Exception as e:
        return {"error": f"网络错误: {str(e)}"}

3.2 数据格式化与增强

原始API响应包含数十个字段，需要针对前端需求进行精简：

def format_weather(raw_data: dict) -> dict:
    return {
        "city": raw_data.get("name"),
        "temp": raw_data.get("main", {}).get("temp"),
        "feels_like": raw_data.get("main", {}).get("feels_like"),
        "description": raw_data["weather"][0]["description"],
        "icon": f"https://openweathermap.org/img/wn/{raw_data['weather'][0]['icon']}@2x.png",
        "update_time": datetime.now().isoformat()
    }

4. 生产级SSE服务优化策略

4.1 性能优化要点

连接管理：使用EventSource对象跟踪活跃连接
心跳机制：定期发送注释行保持连接活跃

async def event_generator():
    while True:
        yield ":heartbeat\n\n"  # 每30秒发送心跳
        await asyncio.sleep(30)

缓存策略：对相同城市的请求复用最近结果

from functools import lru_cache

@lru_cache(maxsize=100)
async def get_cached_weather(city: str):
    return await fetch_weather(city)

4.2 安全增强措施

来源验证：

allowed_origins = ["https://yourdomain.com"]

@app.middleware("http")
async def check_origin(request: Request, call_next):
    if request.headers.get("origin") not in allowed_origins:
        return JSONResponse({"error": "Forbidden"}, status_code=403)
    return await call_next(request)

速率限制：

from fastapi import HTTPException
from slowapi import Limiter
from slowapi.util import get_remote_address

limiter = Limiter(key_func=get_remote_address)

@app.get("/sse/weather")
@limiter.limit("10/minute")
async def weather_sse(request: Request):
    # ...

5. 客户端集成实战示例

5.1 浏览器端实现

<!DOCTYPE html>
<html>
<body>
  <div id="weather"></div>
  
  <script>
    const eventSource = new EventSource('/sse/weather?city=Beijing');
    
    eventSource.onmessage = (event) => {
      const data = JSON.parse(event.data);
      document.getElementById('weather').innerHTML = `
        <h2>${data.city}天气</h2>
        <img src="${data.icon}" alt="天气图标">
        <p>温度: ${data.temp}°C (体感 ${data.feels_like}°C)</p>
        <p>${data.description}</p>
        <small>最后更新: ${new Date(data.update_time).toLocaleString()}</small>
      `;
    };
    
    eventSource.onerror = () => {
      console.log('连接中断，尝试重连...');
    };
  </script>
</body>
</html>

5.2 服务端调试技巧

使用curl测试SSE端点：

curl -N http://localhost:8000/sse/weather

监控连接状态：

@app.on_event("startup")
async def startup():
    print("SSE端点已启动：/sse/weather")
    print(f"文档访问：http://localhost:8000/docs")

6. 进阶功能扩展

6.1 多城市订阅支持

active_subscriptions = {}

@app.websocket("/ws/subscribe")
async def websocket_subscribe(websocket: WebSocket):
    await websocket.accept()
    city = await websocket.receive_text()
    
    if city not in active_subscriptions:
        active_subscriptions[city] = []
    active_subscriptions[city].append(websocket)
    
    try:
        while True:
            await websocket.receive_text()  # 保持连接
    except:
        active_subscriptions[city].remove(websocket)

6.2 历史数据存储

from sqlalchemy import create_engine, Column, Integer, String, Float
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

Base = declarative_base()

class WeatherRecord(Base):
    __tablename__ = 'weather_history'
    id = Column(Integer, primary_key=True)
    city = Column(String)
    temperature = Column(Float)
    recorded_at = Column(String)

engine = create_engine('sqlite:///weather.db')
Base.metadata.create_all(engine)
Session = sessionmaker(bind=engine)

7. 性能监控与运维

7.1 Prometheus指标集成

from prometheus_client import Counter, Gauge

WEATHER_REQUESTS = Counter(
    'weather_requests_total',
    'Total weather API requests',
    ['city']
)
CONNECTIONS_GAUGE = Gauge(
    'sse_connections_current',
    'Current active SSE connections'
)

@app.get("/sse/weather")
async def weather_sse(request: Request, city: str = "Beijing"):
    WEATHER_REQUESTS.labels(city=city).inc()
    CONNECTIONS_GAUGE.inc()
    
    async def generator():
        try:
            # ...原有逻辑...
        finally:
            CONNECTIONS_GAUGE.dec()
    
    return StreamingResponse(generator())

7.2 日志结构化配置

import logging
from pythonjsonlogger import jsonlogger

logger = logging.getLogger("weather-sse")
handler = logging.StreamHandler()
formatter = jsonlogger.JsonFormatter(
    '%(asctime)s %(levelname)s %(message)s %(module)s %(funcName)s'
)
handler.setFormatter(formatter)
logger.addHandler(handler)
logger.setLevel(logging.INFO)

在代码关键点添加日志记录：

logger.info("SSE连接建立", extra={"client": request.client.host})
logger.warning("API调用受限", extra={"city": city, "retry_after": 60})