kubenetworks/kubevpn

package main

// this is a very simplified version of https://github.com/hashicorp/go-retryablehttp
// reason we pulled in here is because we use gock for testing this tool, and gock does
// not work very well with go-retryablehttp as gock replaces transport required by go-retryablehttp

import (
    "io"
    "math"
    "net/http"
    "time"
)

const (
    maxRetries   = 4
    retryWaitMin = 2 * time.Second
    retryWaitMax = 10 * time.Second
)

// getWithRetry is basically http.Get with retries
// we cannot use RoundTripper as gock (lib we use for testing)
// overrides the Transport and thus we cannot test our retryable transport
func getWithRetry(uri string) (*http.Response, error) {
    var resp *http.Response
    var err error

    for i := 0; i < maxRetries; i++ {
        resp, err = http.Get(uri)
        shouldRetry := checkRetry(resp, err)
        if !shouldRetry {
            break
        }

        drainBody(resp.Body)
        wait := backoff(retryWaitMin, retryWaitMax, i)
        <-time.After(wait)
    }

    return resp, err
}

func checkRetry(resp *http.Response, err error) bool {
    return resp != nil && resp.StatusCode == http.StatusNotFound
}

func drainBody(b io.ReadCloser) {
    defer b.Close()
    io.Copy(io.Discard, io.LimitReader(b, int64(4096)))
}

func backoff(min, max time.Duration, attemptNum int) time.Duration {
    mult := math.Pow(2, float64(attemptNum)) * float64(min)
    sleep := time.Duration(mult)
    if float64(sleep) != mult || sleep > max {
        sleep = max
    }
    return sleep
}