@Override
  public void postCompletedCreateTableAction(ObserverContext<MasterCoprocessorEnvironment> ctx,
    TableDescriptor desc, RegionInfo[] regions) throws IOException {
    if (!createFailedOnce && !desc.getTableName().isSystemTable()) {
      createFailedOnce = true;
      throw new IOException("execute postCompletedCreateTableAction failed once.");
    }
  }
A bad Master Observer to prevent user to create/delete table once.
hbase-server/src/test/java/org/apache/hadoop/hbase/coprocessor/BadMasterObserverForCreateDeleteTable.java