github.com/timstclair/heapster@v0.20.0-alpha1/Godeps/_workspace/src/golang.org/x/oauth2/google/appengine.go (about)

     1  // Copyright 2014 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package google
     6  
     7  import (
     8  	"sort"
     9  	"strings"
    10  	"sync"
    11  	"time"
    12  
    13  	"golang.org/x/net/context"
    14  	"golang.org/x/oauth2"
    15  )
    16  
    17  // Set at init time by appenginevm_hook.go. If true, we are on App Engine Managed VMs.
    18  var appengineVM bool
    19  
    20  // Set at init time by appengine_hook.go. If nil, we're not on App Engine.
    21  var appengineTokenFunc func(c context.Context, scopes ...string) (token string, expiry time.Time, err error)
    22  
    23  // AppEngineTokenSource returns a token source that fetches tokens
    24  // issued to the current App Engine application's service account.
    25  // If you are implementing a 3-legged OAuth 2.0 flow on App Engine
    26  // that involves user accounts, see oauth2.Config instead.
    27  //
    28  // The provided context must have come from appengine.NewContext.
    29  func AppEngineTokenSource(ctx context.Context, scope ...string) oauth2.TokenSource {
    30  	if appengineTokenFunc == nil {
    31  		panic("google: AppEngineTokenSource can only be used on App Engine.")
    32  	}
    33  	scopes := append([]string{}, scope...)
    34  	sort.Strings(scopes)
    35  	return &appEngineTokenSource{
    36  		ctx:    ctx,
    37  		scopes: scopes,
    38  		key:    strings.Join(scopes, " "),
    39  	}
    40  }
    41  
    42  // aeTokens helps the fetched tokens to be reused until their expiration.
    43  var (
    44  	aeTokensMu sync.Mutex
    45  	aeTokens   = make(map[string]*tokenLock) // key is space-separated scopes
    46  )
    47  
    48  type tokenLock struct {
    49  	mu sync.Mutex // guards t; held while fetching or updating t
    50  	t  *oauth2.Token
    51  }
    52  
    53  type appEngineTokenSource struct {
    54  	ctx    context.Context
    55  	scopes []string
    56  	key    string // to aeTokens map; space-separated scopes
    57  }
    58  
    59  func (ts *appEngineTokenSource) Token() (*oauth2.Token, error) {
    60  	if appengineTokenFunc == nil {
    61  		panic("google: AppEngineTokenSource can only be used on App Engine.")
    62  	}
    63  
    64  	aeTokensMu.Lock()
    65  	tok, ok := aeTokens[ts.key]
    66  	if !ok {
    67  		tok = &tokenLock{}
    68  		aeTokens[ts.key] = tok
    69  	}
    70  	aeTokensMu.Unlock()
    71  
    72  	tok.mu.Lock()
    73  	defer tok.mu.Unlock()
    74  	if tok.t.Valid() {
    75  		return tok.t, nil
    76  	}
    77  	access, exp, err := appengineTokenFunc(ts.ctx, ts.scopes...)
    78  	if err != nil {
    79  		return nil, err
    80  	}
    81  	tok.t = &oauth2.Token{
    82  		AccessToken: access,
    83  		Expiry:      exp,
    84  	}
    85  	return tok.t, nil
    86  }