Golang技巧之重试机制详解

package retry
import (
    "time"
)
type Retry struct {
    retryCount        int           // 最大重试次数
    retryDelay        time.Duration // 重试之间的延迟
    retryTimeout      time.Duration // 超时重试时间
    retryIntervalFunc func(int) time.Duration
}
type RetriableError struct {
    error error
}
func (e RetriableError) Error() string {
    return e.error.Error()
}
// 重试方法
func (r *Retry) Retry(fn func() error) error {
    retryStart := time.Now()
    var err error
    retryCount := 0
    for {
        duration := r.retryIntervalFunc(retryCount)
        time.Sleep(duration)
        err = fn()
        if err == nil {
            return nil
        }
        if _, ok := err.(RetriableError); ok {
            if retryCount < r.retryCount-1 {
                retryCount++
                continue
            }
            break
        }
        if retryStart.Add(r.retryTimeout).Before(time.Now()) {
            break
        }
    }
    return err
}
func New(
    retryCount int,
    retryDelay time.Duration,
    retryTimeout time.Duration,
    retryIntervalFunc func(attempt int) time.Duration,
) *Retry {
    return &Retry{
        retryCount:        retryCount,
        retryDelay:        retryDelay,
        retryTimeout:      retryTimeout,
        retryIntervalFunc: retryIntervalFunc,
    }
}
func ExampleRetry() {
    r := New(3, 1*time.Second, 5*time.Minute, func(attempt int) time.Duration {
        return r.retryDelay
    })
    err := r.Retry(func() error {
        // Do some work here
        return RetriableError{error: errors.New("foo")}
    })
    if err != nil {
        panic(err)
    }
}

func ExampleRemoteAPICall() {
    r := New(5, 1*time.Second, 5*time.Minute, func(attempt int) time.Duration {
        return r.retryDelay
    })
    resp, err := r.Retry(func() error {
        r, err := http.NewRequest("GET", "<http://api.example.com>", nil)
        if err != nil {
            return RetriableError{error: err}
        }
        client := &http.Client{}
        resp, err := client.Do(r)
        if err != nil {
            return RetriableError{error: err}
        }
        if resp.StatusCode != http.StatusOK {
            return RetriableError{error: fmt.Errorf("Unexpected status code (%v)", resp.Status)}
        }
        // 远程API调用成功，我们将返回数据。
        return nil
    })