cloudinit/datasource/datasource.go

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2014-03-18 09:00:41 -07:00
package datasource
import (
"errors"
"fmt"
"io/ioutil"
"log"
"math"
"net"
"net/http"
neturl "net/url"
"strings"
"time"
)
const (
HTTP_2xx = 2
HTTP_4xx = 4
maxTimeout = time.Second * 5
maxRetries = 15
)
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type Datasource interface {
Fetch() ([]byte, error)
Type() string
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}
// HTTP client timeout
// This one is low since exponential backoff will kick off too.
var timeout = time.Duration(2) * time.Second
func dialTimeout(network, addr string) (net.Conn, error) {
deadline := time.Now().Add(timeout)
c, err := net.DialTimeout(network, addr, timeout)
if err != nil {
return nil, err
}
c.SetDeadline(deadline)
return c, nil
}
// Fetches user-data url with support for exponential backoff and maximum retries
func fetchURL(rawurl string) ([]byte, error) {
if rawurl == "" {
return nil, errors.New("user-data URL is empty. Skipping.")
}
url, err := neturl.Parse(rawurl)
if err != nil {
return nil, err
}
// Unfortunately, url.Parse is too generic to throw errors if a URL does not
// have a valid HTTP scheme. So, we have to do this extra validation
if !strings.HasPrefix(url.Scheme, "http") {
return nil, fmt.Errorf("user-data URL %s does not have a valid HTTP scheme. Skipping.", rawurl)
}
userdataURL := url.String()
// We need to create our own client in order to add timeout support.
// TODO(c4milo) Replace it once Go 1.3 is officially used by CoreOS
// More info: https://code.google.com/p/go/source/detail?r=ada6f2d5f99f
transport := &http.Transport{
Dial: dialTimeout,
}
client := &http.Client{
Transport: transport,
}
for retry := 1; retry <= maxRetries; retry++ {
log.Printf("Fetching user-data from %s. Attempt #%d", userdataURL, retry)
resp, err := client.Get(userdataURL)
if err == nil {
defer resp.Body.Close()
status := resp.StatusCode / 100
if status == HTTP_2xx {
return ioutil.ReadAll(resp.Body)
}
if status == HTTP_4xx {
return nil, fmt.Errorf("user-data not found. HTTP status code: %d", resp.StatusCode)
}
log.Printf("user-data not found. HTTP status code: %d", resp.StatusCode)
} else {
log.Printf("unable to fetch user-data: %s", err.Error())
}
duration := time.Millisecond * time.Duration((math.Pow(float64(2), float64(retry)) * 100))
if duration > maxTimeout {
duration = maxTimeout
}
time.Sleep(duration)
}
return nil, fmt.Errorf("unable to fetch user-data. Maximum retries reached: %d", maxRetries)
}