/**
    * 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.regionserver.throttle;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.HBaseInterfaceAudience;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.regionserver.RegionServerServices;
  import org.apache.hadoop.util.ReflectionUtils;
  
  @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.CONFIG)
  public final class CompactionThroughputControllerFactory {
  
    private static final Log LOG = LogFactory.getLog(CompactionThroughputControllerFactory.class);
  
    public static final String HBASE_THROUGHPUT_CONTROLLER_KEY =
        "hbase.regionserver.throughput.controller";
  
    private CompactionThroughputControllerFactory() {
    }
  
    private static final Class<? extends ThroughputController>
        DEFAULT_THROUGHPUT_CONTROLLER_CLASS = PressureAwareCompactionThroughputController.class;
  
    // for backward compatibility and may not be supported in the future
    private static final String DEPRECATED_NAME_OF_PRESSURE_AWARE_THROUGHPUT_CONTROLLER_CLASS =
      "org.apache.hadoop.hbase.regionserver.compactions.PressureAwareCompactionThroughputController";
    private static final String DEPRECATED_NAME_OF_NO_LIMIT_THROUGHPUT_CONTROLLER_CLASS =
      "org.apache.hadoop.hbase.regionserver.compactions.NoLimitThroughputController";
  
    public static ThroughputController create(RegionServerServices server,
        Configuration conf) {
      Class<? extends ThroughputController> clazz = getThroughputControllerClass(conf);
      ThroughputController controller = ReflectionUtils.newInstance(clazz, conf);
      controller.setup(server);
      return controller;
    }
  
    public static Class<? extends ThroughputController> getThroughputControllerClass(
        Configuration conf) {
      String className =
          conf.get(HBASE_THROUGHPUT_CONTROLLER_KEY, DEFAULT_THROUGHPUT_CONTROLLER_CLASS.getName());
      className = resolveDeprecatedClassName(className);
      try {
        return Class.forName(className).asSubclass(ThroughputController.class);
      } catch (Exception e) {
        LOG.warn(
          "Unable to load configured throughput controller '" + className
              + "', load default throughput controller "
              + DEFAULT_THROUGHPUT_CONTROLLER_CLASS.getName() + " instead", e);
        return DEFAULT_THROUGHPUT_CONTROLLER_CLASS;
      }
    }
  
    /**
     * Resolve deprecated class name to keep backward compatibility
     * @param oldName old name of the class
     * @return the new name if there is any
     */
    private static String resolveDeprecatedClassName(String oldName) {
      String className = oldName.trim();
      if (className.equals(DEPRECATED_NAME_OF_PRESSURE_AWARE_THROUGHPUT_CONTROLLER_CLASS)) {
        className = PressureAwareCompactionThroughputController.class.getName();
      } else if (className.equals(DEPRECATED_NAME_OF_NO_LIMIT_THROUGHPUT_CONTROLLER_CLASS)) {
        className = NoLimitThroughputController.class.getName();
      }
      if (!className.equals(oldName)) {
        LOG.warn(oldName + " is deprecated, please use " + className + " instead");
      }
      return className;
    }
  }