content: /**
   *
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you under the Apache License, Version 2.0 (the
   * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package com.alibaba.wasp.master;
  
  import java.util.Collections;
  import java.util.HashSet;
  import java.util.Set;
  
  /**
   * 
   * Lock table when do some DDL
   * 
   */
  public class TableLockManager {
  
    private Set<String> lockTables = Collections
        .synchronizedSet(new HashSet<String>());
    
    public TableLockManager() {
    }
  
    /**
     * lock table, do not wait for ever
     * 
     */
    public synchronized boolean lockTable(String table) {
      if (lockTables.contains(table)) {
        return false;
      } else {
        lockTables.add(table);
        return true;
      }
    }
  
    /**
     * unlock table
     */
    public synchronized void unlockTable(String table) {
      lockTables.remove(table);
    }
  
    public boolean isTableLocked(String table) {
      if (lockTables.contains(table)) {
        return true;
      } else {
        return false;
      }
    }
  
  }
  