使用双检锁优化 Token 获取 (#444)

credential/default_access_token.go

@@ -56,15 +56,19 @@ type ResAccessToken struct {
 
 //GetAccessToken 获取access_token,先从cache中获取，没有则从服务端获取
 func (ak *DefaultAccessToken) GetAccessToken() (accessToken string, err error) {
+	// 先从cache中取
+	accessTokenCacheKey := fmt.Sprintf("%s_access_token_%s", ak.cacheKeyPrefix, ak.appID)
+	if val := ak.cache.Get(accessTokenCacheKey); val != nil {
+		return val.(string), nil
+	}
+
 	//加上lock，是为了防止在并发获取token时，cache刚好失效，导致从微信服务器上获取到不同token
 	ak.accessTokenLock.Lock()
 	defer ak.accessTokenLock.Unlock()
 
-	accessTokenCacheKey := fmt.Sprintf("%s_access_token_%s", ak.cacheKeyPrefix, ak.appID)
-	val := ak.cache.Get(accessTokenCacheKey)
-	if val != nil {
-		accessToken = val.(string)
-		return
+	// 双检，防止重复从微信服务器获取
+	if val := ak.cache.Get(accessTokenCacheKey); val != nil {
+		return val.(string), nil
 	}
 
 	//cache失效，从微信服务器获取

credential/default_js_ticket.go

@@ -42,16 +42,20 @@ type ResTicket struct {
 
 //GetTicket 获取jsapi_ticket
 func (js *DefaultJsTicket) GetTicket(accessToken string) (ticketStr string, err error) {
+	//先从cache中取
+	jsAPITicketCacheKey := fmt.Sprintf("%s_jsapi_ticket_%s", js.cacheKeyPrefix, js.appID)
+	if val := js.cache.Get(jsAPITicketCacheKey); val != nil {
+		return val.(string), nil
+	}
+
 	js.jsAPITicketLock.Lock()
 	defer js.jsAPITicketLock.Unlock()
 
-	//先从cache中取
-	jsAPITicketCacheKey := fmt.Sprintf("%s_jsapi_ticket_%s", js.cacheKeyPrefix, js.appID)
-	val := js.cache.Get(jsAPITicketCacheKey)
-	if val != nil {
-		ticketStr = val.(string)
-		return
+	// 双检，防止重复从微信服务器获取
+	if val := js.cache.Get(jsAPITicketCacheKey); val != nil {
+		return val.(string), nil
 	}
+
 	var ticket ResTicket
 	ticket, err = GetTicketFromServer(accessToken)
 	if err != nil {