@Override
      public Void call() throws Exception {
        try {
          AccessControlClient.grant(connection, namespace, user, actions);
        } catch (Throwable t) {
          LOG.error("grant failed: ", t);
        }
        return null;
      }
Grant permissions on a namespace to the given user using AccessControl Client. Will wait until
all active AccessController instances have updated their permissions caches or will throw an
exception upon timeout (10 seconds).
hbase-server/src/test/java/org/apache/hadoop/hbase/security/access/SecureTestUtil.java