8.12 面试重点与最佳实践¶

// 好的服务拆分示例
type UserService struct {
    // 只关注用户相关功能
    userRepo UserRepository
    authService AuthService
}

type OrderService struct {
    // 只关注订单相关功能
    orderRepo OrderRepository
    paymentClient PaymentClient
}

// RESTful API设计
// GET /api/v1/users/{id}
// POST /api/v1/users
// PUT /api/v1/users/{id}
// DELETE /api/v1/users/{id}

type UserAPI struct {
    service UserService
}

func (api *UserAPI) GetUser(c *gin.Context) {
    id := c.Param("id")
    user, err := api.service.GetUserByID(id)
    if err != nil {
        c.JSON(http.StatusNotFound, gin.H{"error": "User not found"})
        return
    }
    c.JSON(http.StatusOK, user)
}

func (c *Client) CallService(ctx context.Context, req *Request) (*Response, error) {
    // 设置超时上下文
    ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
    defer cancel()

    return c.httpClient.Do(ctx, req)
}

func (c *Client) CallWithRetry(ctx context.Context, req *Request) (*Response, error) {
    var lastErr error
    for i := 0; i < 3; i++ {
        resp, err := c.CallService(ctx, req)
        if err == nil {
            return resp, nil
        }
        lastErr = err

        // 指数退避
        time.Sleep(time.Duration(1<<i) * time.Second)
    }
    return nil, lastErr
}

var (
    requestDuration = prometheus.NewHistogramVec(
        prometheus.HistogramOpts{
            Name: "http_request_duration_seconds",
            Help: "HTTP request duration",
        },
        []string{"method", "endpoint", "status"},
    )
)

func MetricsMiddleware() gin.HandlerFunc {
    return func(c *gin.Context) {
        start := time.Now()
        c.Next()

        duration := time.Since(start).Seconds()
        requestDuration.WithLabelValues(
            c.Request.Method,
            c.FullPath(),
            strconv.Itoa(c.Writer.Status()),
        ).Observe(duration)
    }
}

type ErrorResponse struct {
    Code    int    `json:"code"`
    Message string `json:"message"`
    TraceID string `json:"trace_id"`
}

func ErrorMiddleware() gin.HandlerFunc {
    return func(c *gin.Context) {
        c.Next()

        if len(c.Errors) > 0 {
            err := c.Errors.Last()
            traceID := c.GetHeader("X-Trace-ID")

            c.JSON(http.StatusInternalServerError, ErrorResponse{
                Code:    500,
                Message: err.Error(),
                TraceID: traceID,
            })
        }
    }
}