golang框架限流与熔断的最佳实践有哪些？

import (
    "context"
    "net/http"
    "sync/atomic"
    "time"

    "github.com/goccy/go-limiter"
)

// LimitedHandler 是一个限流中间件。
func LimitedHandler(limit float64) func(http.Handler) http.Handler {
    return func(next http.Handler) http.Handler {
        limiter := limiter.NewFixed(limit, time.Second)
        return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
            if rate, _, ok := limiter.TakeAvailable(context.Background(), 1); !ok {
                http.Error(w, "Too Many Requests", http.StatusTooManyRequests)
                return
            }
            atomic.AddInt64(&inFlightRequests, int64(rate))
            defer atomic.AddInt64(&inFlightRequests, -int64(rate))
            next.ServeHTTP(w, r)
        })
    }
}

// inFlightRequests 用于跟踪正在处理的请求数量。
var inFlightRequests int64

import (
    "context"
    "errors"
    "time"

    "github.com/robfig/cron/v3"
)

// CircuitBreaker 是一个熔断器。
type CircuitBreaker struct {
    state       int64
    closedAt    time.Time
    failedCount uint64
}

const (
    closedState   = 0
    openState     = 1
    halfOpenState = 2
)

// closedTimeout 是熔断器处于闭合状态的最大时长。
const closedTimeout = 30 * time.Second

// halfOpenTimeout 是熔断器处于半开状态的最大时长。
const halfOpenTimeout = 30 * time.Second

// threshold 是触发熔断的失败请求次数阈值。
const threshold = 5

// NewCircuitBreaker 创建一个新的熔断器。
func NewCircuitBreaker() *CircuitBreaker {
    return &CircuitBreaker{
        state:       closedState,
        closedAt:    time.Now(),
        failedCount: 0,
    }
}

// AllowCheck 允许或拒绝请求。
func (cb *CircuitBreaker) AllowCheck() error {
    switch cb.state {
    case closedState:
        if time.Since(cb.closedAt) > closedTimeout {
            cb.setState(halfOpenState)
            cb.failedCount = 0
        }
        return nil
    case openState:
        return errors.New("Circuit breaker open")
    case halfOpenState:
        if time.Since(cb.closedAt) > halfOpenTimeout {
            cb.setState(openState)
            cb.failedCount = 0
        }
        return nil
    }
    return errors.New("Invalid circuit breaker state")
}

// TryCall 尝试调用给定的函数，并处理熔断。
func (cb *CircuitBreaker) TryCall(ctx context.Context, call func() error) error {
    if err := cb.AllowCheck(); err != nil {
        return err
    }

    err := call()
    if err != nil {
        cb.failedCount++
        if cb.failedCount >= threshold {
            cb.setState(openState)
            cb.closedAt = time.Now()
        }
    } else {
        cb.setState(closedState)
    }
    return err
}

// setState 更新熔断器的状态。
func (cb *CircuitBreaker) setState(state int64) {
    oldState := atomic.LoadInt64(&cb.state)
    if oldState != state && atomic.CompareAndSwapInt64(&cb.state, oldState, state) {
        cb.closedAt = time.Now()
        switch state {
        case closedState:
            cron.New().Schedule(time.Minute.String(), func() { cb.setState(openState) })
        case openState:
            cron.New().Schedule(time.Second*10.String(), func() { cb.setState(halfOpenState) })
        }
    }
}