@Override
  public boolean addToken(DelegationTokenIdentifier tokenIdentifier,
    DelegationTokenInformation token) {
    DelegationTokenInformation tokenInfo = tokens.putIfAbsent(tokenIdentifier, token);
    LOG.trace("addToken: tokenIdentifier = {}, added = {}", tokenIdentifier, (tokenInfo == null));
    return (tokenInfo == null);
  }
Default in-memory token store implementation.
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/security/MemoryTokenStore.java