content: /*
   * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
   * (the "License"). You may not use this work except in compliance with the License, which is
   * available at www.apache.org/licenses/LICENSE-2.0
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
   * either express or implied, as more fully set forth in the License.
   *
   * See the NOTICE file distributed with this work for information regarding copyright ownership.
   */
  
  package alluxio.conf;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.util.LinkedList;
  import java.util.List;
  import java.util.Map;
  import javax.annotation.concurrent.ThreadSafe;
  
  /**
   * Registry of all reconfigurable listeners.
   */
  @ThreadSafe
  public class ReconfigurableRegistry {
    private static final Logger LOG = LoggerFactory.getLogger(ReconfigurableRegistry.class);
    private static final List<Reconfigurable> LISTENER_LIST = new LinkedList<>();
  
    /**
     * Add a listener.
     *
     * @param listener the given property listener
     */
    public static synchronized void register(Reconfigurable listener) {
      LISTENER_LIST.add(listener);
    }
  
    /**
     * remove the listener related to the given property.
     * @param listener the listener
     * @return true if the instance is removed
     */
    public static synchronized boolean unregister(Reconfigurable listener) {
      return LISTENER_LIST.remove(listener);
    }
  
    /**
     * When the property was reconfigured, this function will be invoked.
     * This property listeners will be notified.
     *
     * @return false if no listener related to the given property, otherwise, return false
     */
    public static synchronized boolean update() {
      for (Reconfigurable listener : LISTENER_LIST) {
        try {
          listener.update();
        } catch (Throwable t) {
          LOG.error("Error while update changed properties for {}", listener, t);
        }
      }
      return true;
    }
  
    // prevent instantiation
    private ReconfigurableRegistry() {}
  
    /**
     * When the property was reconfigured, this function will be invoked.
     * This property listeners will be notified.
     *
     * @param changedProperties the changed properties
     */
    public static synchronized void update(Map<PropertyKey, Object> changedProperties) {
      for (Reconfigurable listener : LISTENER_LIST) {
        try {
          listener.update(changedProperties);
        } catch (Throwable t) {
          LOG.error("Error while update changed properties {} for {}",
              changedProperties, listener, t);
        }
      }
    }
  }
  