feat(go-sdk): Automatically refresh expired authentication tokens

go/rtl/auth.go

@@ -10,6 +10,7 @@ import (
 	"net/url"
 	"os"
 	"reflect"
+	"sync"
 	"time"
 
 	"golang.org/x/oauth2"
@@ -39,6 +40,47 @@ func (t *transportWithHeaders) RoundTrip(req *http.Request) (*http.Response, err
 type AuthSession struct {
 	Config ApiSettings
 	Client http.Client
+	token  *oauth2.Token
+	source oauth2.TokenSource
+	mu     sync.RWMutex
+}
+
+const tokenLeeway = 10 * time.Second
+
+func (s *AuthSession) IsActive() bool {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+	if s.token == nil {
+		return false
+	}
+	return s.token.Expiry.After(time.Now().Add(tokenLeeway))
+}
+
+func (s *AuthSession) Login() (*oauth2.Token, error) {
+	// First, check with a read lock to avoid contention if the token is valid.
+	s.mu.RLock()
+	if s.token != nil && s.token.Expiry.After(time.Now().Add(tokenLeeway)) {
+		token := s.token
+		s.mu.RUnlock()
+		return token, nil
+	}
+	s.mu.RUnlock()
+
+	// If the token is invalid or nil, acquire a write lock to refresh it.
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	// Re-check after obtaining the write lock, in case another goroutine refreshed it.
+	if s.token != nil && s.token.Expiry.After(time.Now().Add(tokenLeeway)) {
+		return s.token, nil
+	}
+
+	token, err := s.source.Token()
+	if err != nil {
+		return nil, err
+	}
+	s.token = token
+	return token, nil
 }
 
 func NewAuthSession(config ApiSettings) *AuthSession {
@@ -74,21 +116,27 @@ func NewAuthSessionWithTransport(config ApiSettings, transport http.RoundTripper
 		&http.Client{Transport: appIdHeaderTransport},
 	)
 
+	source := oauthConfig.TokenSource(ctx)
+
 	// Make use of oauth2 transport to handle token management
 	oauthTransport := &oauth2.Transport{
-		Source: oauthConfig.TokenSource(ctx),
+		Source: source,
 		// Will set "x-looker-appid" Header on all other requests
 		Base: appIdHeaderTransport,
 	}
 
 	return &AuthSession{
 		Config: config,
 		Client: http.Client{Transport: oauthTransport},
+		source: source,
 	}
 }
 
 func (s *AuthSession) Do(result interface{}, method, ver, path string, reqPars map[string]interface{}, body interface{}, options *ApiSettings) error {
-
+	_, err := s.Login()
+	if err != nil {
+		return err
+	}
 	// prepare URL
 	u := fmt.Sprintf("%s/api%s%s", s.Config.BaseUrl, ver, path)