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 org.apache.bookkeeper.common.component;
  
  import java.io.IOException;
  import java.lang.Thread.UncaughtExceptionHandler;
  import java.util.Set;
  import java.util.concurrent.CopyOnWriteArraySet;
  import lombok.extern.slf4j.Slf4j;
  import org.apache.bookkeeper.common.conf.ComponentConfiguration;
  import org.apache.bookkeeper.stats.StatsLogger;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * A mix of {@link AbstractComponent} and {@link LifecycleComponent}.
   */
  @Slf4j
  public abstract class AbstractLifecycleComponent<ConfT extends ComponentConfiguration>
      extends AbstractComponent<ConfT> implements LifecycleComponent {
  
      private static final Logger LOG = LoggerFactory.getLogger(AbstractLifecycleComponent.class);
  
      protected final Lifecycle lifecycle = new Lifecycle();
      private final Set<LifecycleListener> listeners = new CopyOnWriteArraySet<>();
      protected final StatsLogger statsLogger;
      protected volatile UncaughtExceptionHandler uncaughtExceptionHandler;
  
      protected AbstractLifecycleComponent(String componentName,
                                           ConfT conf,
                                           StatsLogger statsLogger) {
          super(componentName, conf);
          this.statsLogger = statsLogger;
      }
  
      @Override
      public void setExceptionHandler(UncaughtExceptionHandler handler) {
          this.uncaughtExceptionHandler = handler;
      }
  
      protected StatsLogger getStatsLogger() {
          return statsLogger;
      }
  
      @Override
      public Lifecycle.State lifecycleState() {
          return this.lifecycle.state();
      }
  
      @Override
      public void addLifecycleListener(LifecycleListener listener) {
          listeners.add(listener);
      }
  
      @Override
      public void removeLifecycleListener(LifecycleListener listener) {
          listeners.remove(listener);
      }
  
      @Override
      public void start() {
          if (!lifecycle.canMoveToStarted()) {
              return;
          }
          listeners.forEach(LifecycleListener::beforeStart);
          try {
              doStart();
          } catch (Throwable exc) {
              LOG.error("Failed to start Component: {}", getName(), exc);
              if (uncaughtExceptionHandler != null) {
                  LOG.error("Calling uncaughtExceptionHandler");
                  uncaughtExceptionHandler.uncaughtException(Thread.currentThread(), exc);
              } else {
                  throw exc;
              }
          }
          lifecycle.moveToStarted();
          listeners.forEach(LifecycleListener::afterStart);
      }
  
      protected abstract void doStart();
  
      @Override
      public void stop() {
          if (!lifecycle.canMoveToStopped()) {
              return;
          }
          listeners.forEach(LifecycleListener::beforeStop);
          lifecycle.moveToStopped();
          doStop();
          listeners.forEach(LifecycleListener::afterStop);
      }
  
      protected abstract void doStop();
  
      @Override
      public void close() {
          if (lifecycle.started()) {
              stop();
          }
          if (!lifecycle.canMoveToClosed()) {
              return;
          }
          listeners.forEach(LifecycleListener::beforeClose);
          lifecycle.moveToClosed();
          try {
              doClose();
          } catch (IOException e) {
              log.warn("failed to close {}", componentName, e);
          }
          listeners.forEach(LifecycleListener::afterClose);
      }
  
      protected abstract void doClose() throws IOException;
  
  }
  