vendor/google.golang.org/appengine/internal/metadata.go

   1 // Copyright 2014 Google Inc. All rights reserved.
   2 // Use of this source code is governed by the Apache 2.0
   3 // license that can be found in the LICENSE file.
   4
   5 package internal
   6
   7 // This file has code for accessing metadata.
   8 //
   9 // References:
  10 //      https://cloud.google.com/compute/docs/metadata
  11
  12 import (
  13         "fmt"
  14         "io/ioutil"
  15         "net/http"
  16         "net/url"
  17 )
  18
  19 const (
  20         metadataHost = "metadata"
  21         metadataPath = "/computeMetadata/v1/"
  22 )
  23
  24 var (
  25         metadataRequestHeaders = http.Header{
  26                 "Metadata-Flavor": []string{"Google"},
  27         }
  28 )
  29
  30 // TODO(dsymonds): Do we need to support default values, like Python?
  31 func mustGetMetadata(key string) []byte {
  32         b, err := getMetadata(key)
  33         if err != nil {
  34                 panic(fmt.Sprintf("Metadata fetch failed for '%s': %v", key, err))
  35         }
  36         return b
  37 }
  38
  39 func getMetadata(key string) ([]byte, error) {
  40         // TODO(dsymonds): May need to use url.Parse to support keys with query args.
  41         req := &http.Request{
  42                 Method: "GET",
  43                 URL: &url.URL{
  44                         Scheme: "http",
  45                         Host:   metadataHost,
  46                         Path:   metadataPath + key,
  47                 },
  48                 Header: metadataRequestHeaders,
  49                 Host:   metadataHost,
  50         }
  51         resp, err := http.DefaultClient.Do(req)
  52         if err != nil {
  53                 return nil, err
  54         }
  55         defer resp.Body.Close()
  56         if resp.StatusCode != 200 {
  57                 return nil, fmt.Errorf("metadata server returned HTTP %d", resp.StatusCode)
  58         }
  59         return ioutil.ReadAll(resp.Body)
  60 }