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.cloudstack.poll;
  
  import com.cloud.utils.component.Manager;
  import com.cloud.utils.component.ManagerBase;
  import com.cloud.utils.concurrency.NamedThreadFactory;
  import com.cloud.utils.exception.CloudRuntimeException;
  import com.google.common.base.Preconditions;
  
  import java.util.ArrayList;
  import java.util.List;
  import java.util.concurrent.Executors;
  import java.util.concurrent.ScheduledExecutorService;
  import java.util.concurrent.TimeUnit;
  
  public final class BackgroundPollManagerImpl extends ManagerBase implements BackgroundPollManager, Manager {
  
      private ScheduledExecutorService backgroundPollTaskScheduler;
      private List<BackgroundPollTask> submittedTasks = new ArrayList<>();
      private volatile boolean isConfiguredAndStarted = false;
  
      public long getInitialDelay() {
          return 5000L;
      }
  
      public long getRoundDelay() {
          return 4000L;
      }
  
      @Override
      public boolean start() {
          if (isConfiguredAndStarted) {
              return true;
          }
          backgroundPollTaskScheduler = Executors.newScheduledThreadPool(submittedTasks.size() + 1, new NamedThreadFactory("BackgroundTaskPollManager"));
          for (final BackgroundPollTask task : submittedTasks) {
              Long delay = task.getDelay();
              if (delay == null) {
                  delay = getRoundDelay();
              }
              backgroundPollTaskScheduler.scheduleWithFixedDelay(task, getInitialDelay(), delay, TimeUnit.MILLISECONDS);
              logger.debug("Scheduled background poll task: " + task.getClass().getName());
          }
          isConfiguredAndStarted = true;
          return true;
      }
  
      @Override
      public boolean stop() {
          if (isConfiguredAndStarted) {
              backgroundPollTaskScheduler.shutdown();
          }
          return true;
      }
  
      @Override
      public void submitTask(final BackgroundPollTask task) {
          Preconditions.checkNotNull(task);
          if (isConfiguredAndStarted) {
              throw new CloudRuntimeException("Background Poll Manager cannot accept poll task as it has been configured and started.");
          }
          logger.debug("Background Poll Manager received task: " + task.getClass().getSimpleName());
          submittedTasks.add(task);
      }
  }
  