forked from hairyhenderson/gomplate
/
ec2meta.go
129 lines (109 loc) · 2.64 KB
/
ec2meta.go
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package aws
import (
"encoding/json"
"io/ioutil"
"log"
"net/http"
"strings"
"time"
)
// DefaultEndpoint -
const DefaultEndpoint = "http://169.254.169.254"
// Ec2Meta -
type Ec2Meta struct {
Endpoint string
Client *http.Client
nonAWS bool
cache map[string]string
}
// NewEc2Meta -
func NewEc2Meta() *Ec2Meta {
return &Ec2Meta{cache: make(map[string]string)}
}
// returnDefault -
func returnDefault(def []string) string {
if len(def) > 0 {
return def[0]
}
return ""
}
func unreachable(err error) bool {
if strings.Contains(err.Error(), "request canceled") ||
strings.Contains(err.Error(), "no route to host") ||
strings.Contains(err.Error(), "host is down") {
return true
}
return false
}
func (e *Ec2Meta) retrieveMetadata(url string, def ...string) string {
if value, ok := e.cache[url]; ok {
return value
}
if e.nonAWS {
return returnDefault(def)
}
if e.Client == nil {
e.Client = &http.Client{Timeout: 500 * time.Millisecond}
}
resp, err := e.Client.Get(url)
if err != nil {
if unreachable(err) {
e.nonAWS = true
}
return returnDefault(def)
}
defer resp.Body.Close()
if resp.StatusCode > 399 {
return returnDefault(def)
}
body, err := ioutil.ReadAll(resp.Body)
if err != nil {
log.Fatalf("Failed to read response body from %s: %v", url, err)
}
value := strings.TrimSpace(string(body))
e.cache[url] = value
return value
}
// Meta -
func (e *Ec2Meta) Meta(key string, def ...string) string {
if e.Endpoint == "" {
e.Endpoint = DefaultEndpoint
}
url := e.Endpoint + "/latest/meta-data/" + key
return e.retrieveMetadata(url, def...)
}
// Dynamic -
func (e *Ec2Meta) Dynamic(key string, def ...string) string {
if e.Endpoint == "" {
e.Endpoint = DefaultEndpoint
}
url := e.Endpoint + "/latest/dynamic/" + key
return e.retrieveMetadata(url, def...)
}
// Region -
func (e *Ec2Meta) Region(def ...string) string {
defaultRegion := returnDefault(def)
if defaultRegion == "" {
defaultRegion = "unknown"
}
doc := e.Dynamic("instance-identity/document", `{"region":"`+defaultRegion+`"}`)
obj := &InstanceDocument{
Region: defaultRegion,
}
err := json.Unmarshal([]byte(doc), &obj)
if err != nil {
log.Fatalf("Unable to unmarshal JSON object %s: %v", doc, err)
}
return obj.Region
}
// InstanceDocument -
type InstanceDocument struct {
PrivateIP string `json:"privateIp"`
AvailabilityZone string `json:"availabilityZone"`
InstanceID string `json:"InstanceId"`
InstanceType string `json:"InstanceType"`
AccountID string `json:"AccountId"`
ImageID string `json:"imageId"`
Architecture string `json:"architecture"`
Region string `json:"region"`
}