hbase-server/src/main/java/org/apache/hadoop/hbase/master/balancer/LoadBalancerFactory.java

/**
 * 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 org.apache.hadoop.hbase.master.balancer;

import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.HConstants;
import org.apache.hadoop.hbase.master.LoadBalancer;
import org.apache.hadoop.util.ReflectionUtils;

/**
 * The class that creates a load balancer from a conf.
 */
@InterfaceAudience.Private
public class LoadBalancerFactory {

  /**
   * The default {@link LoadBalancer} class. 
   *
   * @return The Class for the default {@link LoadBalancer}.
   */
  public static Class<? extends LoadBalancer> getDefaultLoadBalancerClass() {
    return StochasticLoadBalancer.class;
  }

  /**
   * Create a loadbalancer from the given conf.
   * @param conf
   * @return A {@link LoadBalancer}
   */
  public static LoadBalancer getLoadBalancer(Configuration conf) {

    // Create the balancer
    Class<? extends LoadBalancer> balancerKlass =
        conf.getClass(HConstants.HBASE_MASTER_LOADBALANCER_CLASS, getDefaultLoadBalancerClass(),
          LoadBalancer.class);
    return ReflectionUtils.newInstance(balancerKlass, conf);

  }
}