public LlapTokenClient withCurrentToken(Token<LlapTokenIdentifier> token) {
    this.currentToken = token;
    return this;
  }
An initial token can be set with this method. A typical path is
LlapTaskCommunicator -- LlapProtocolClientProxy::initPeriodicTokenRefresh. If the LlapTaskCommunicator is
instantiated an initial token, it can be used for subsequent calls, even for fetching new tokens.
llap-client/src/java/org/apache/hadoop/hive/llap/security/LlapTokenClient.java