Feat: support ecs ramrole (#292)

feat: refine credentials, add ecs ram role

credentials.go

@@ -10,60 +10,31 @@ type Credentials struct {
 	SecurityToken   string
 }
 
-const DEFAULT_EXPIRED_FACTOR = 0.8
-
 // Expirable credentials with an expiration.
-type TempCredentials struct {
+type tempCredentials struct {
 	Credentials
-	expiredFactor      float64
-	expirationInMills  int64 // The time when the credentials expires, unix timestamp in millis
-	lastUpdatedInMills int64
+	Expiration     time.Time // The time when the credentials expires, unix timestamp in millis
+	LastUpdateTime time.Time
 }
 
-func NewTempCredentials(accessKeyId, accessKeySecret, securityToken string,
-	expirationInMills, lastUpdatedInMills int64) *TempCredentials {
+func newTempCredentials(accessKeyId, accessKeySecret, securityToken string,
+	expiration time.Time, lastUpdateTime time.Time) *tempCredentials {
 
-	return &TempCredentials{
+	return &tempCredentials{
 		Credentials: Credentials{
 			AccessKeyID:     accessKeyId,
 			AccessKeySecret: accessKeySecret,
 			SecurityToken:   securityToken,
 		},
-		expirationInMills:  expirationInMills,
-		lastUpdatedInMills: lastUpdatedInMills,
-		expiredFactor:      DEFAULT_EXPIRED_FACTOR,
-	}
-}
-
-// @param factor must > 0.0 and <= 1.0, the less the factor is,
-// the more frequently the credentials will be updated.
-//
-// If factor is set to 0, the credentials will be fetched every time
-// [GetCredentials] is called.
-//
-// If factor is set to 1, the credentials will be fetched only when expired .
-func (t *TempCredentials) WithExpiredFactor(factor float64) *TempCredentials {
-	if factor > 0.0 && factor <= 1.0 {
-		t.expiredFactor = factor
+		Expiration:     expiration,
+		LastUpdateTime: lastUpdateTime,
 	}
-	return t
 }
 
-// Returns true if credentials has expired already or will expire soon.
-func (t *TempCredentials) ShouldRefresh() bool {
-	nowInMills := time.Now().UnixNano() / 1e6
-	if nowInMills >= t.expirationInMills {
-		return true
-	}
-	duration := (float64)(t.expirationInMills-t.lastUpdatedInMills) * t.expiredFactor
-	if duration < 0.0 { // check here
-		duration = 0
-	}
-	return (nowInMills - t.lastUpdatedInMills) >= int64(duration)
+func (t *tempCredentials) isExpired() bool {
+	return time.Now().After(t.Expiration)
 }
 
-// Returns true if credentials has expired already.
-func (t *TempCredentials) HasExpired() bool {
-	nowInMills := time.Now().UnixNano() / 1e6
-	return nowInMills >= t.expirationInMills
+func (t *tempCredentials) isValid() bool {
+	return t.Credentials.AccessKeyID != "" && t.Credentials.AccessKeySecret != "" && !t.Expiration.IsZero()
 }