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.ambari.server.events.listeners.alerts;
  
  import java.util.Collection;
  import java.util.Collections;
  
  import org.apache.ambari.server.EagerSingleton;
  import org.apache.ambari.server.agent.AlertDefinitionCommand;
  import org.apache.ambari.server.agent.HeartBeatResponse;
  import org.apache.ambari.server.events.AlertHashInvalidationEvent;
  import org.apache.ambari.server.events.AmbariEvent.AmbariEventType;
  import org.apache.ambari.server.events.ClusterEvent;
  import org.apache.ambari.server.events.ServiceComponentUninstalledEvent;
  import org.apache.ambari.server.events.publishers.AmbariEventPublisher;
  import org.apache.ambari.server.state.alert.AlertDefinitionHash;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import com.google.common.eventbus.AllowConcurrentEvents;
  import com.google.common.eventbus.Subscribe;
  import com.google.inject.Inject;
  import com.google.inject.Provider;
  import com.google.inject.Singleton;
  
  /**
   * The {@link AlertHashInvalidationListener} is used to respond to
   * {@link AlertHashInvalidationEvent} and {@link ClusterEvent} instances and
   * ensure that the {@link AlertDefinitionCommand}s are enqueued for the
   * {@link HeartBeatResponse}.
   * <p/>
   * <ul>
   * <li>{@link ClusterEvent} - invalidates all alerts across the cluster</li>
   * <li>{@link AlertHashInvalidationEvent} - invalidates a specific alert across
   * affected hosts</li>
   * </ul>
   */
  @Singleton
  @EagerSingleton
  public class AlertHashInvalidationListener {
    /**
     * Logger.
     */
    private static final Logger LOG = LoggerFactory.getLogger(AlertHashInvalidationListener.class);
  
    /**
     * Invalidates hosts so that they can receive updated alert definition
     * commands.
     */
    @Inject
    private Provider<AlertDefinitionHash> m_alertDefinitionHash;
  
    /**
     * Constructor.
     *
     * @param publisher
     */
    @Inject
    public AlertHashInvalidationListener(AmbariEventPublisher publisher) {
      publisher.register(this);
    }
  
    /**
     * Handles {@link AlertHashInvalidationEvent} by performing the following
     * tasks:
     * <ul>
     * <li>Enqueuing {@link AlertDefinitionCommand}</li>
     * </ul>
     *
     * @param event
     *          the event being handled.
     */
    @Subscribe
    @AllowConcurrentEvents
    public void onAmbariEvent(AlertHashInvalidationEvent event) {
      LOG.debug("Received event {}", event);
  
      Collection<String> hosts = event.getHosts();
      long clusterId = event.getClusterId();
  
      // no hosts, nothing to do
      if (null == hosts || hosts.isEmpty()) {
        return;
      }
  
      AlertDefinitionHash hash = m_alertDefinitionHash.get();
      hash.enqueueAgentCommands(clusterId, hosts);
    }
  
    /**
     * Handles {@link AlertHashInvalidationEvent} by performing the following
     * tasks:
     * <ul>
     * <li>Alert has invalidation</li>
     * <li>Enqueuing {@link AlertDefinitionCommand}</li>
     * </ul>
     */
    @Subscribe
    @AllowConcurrentEvents
    public void onEvent(ServiceComponentUninstalledEvent event) {
      LOG.debug("Received event {}", event);
  
      long clusterId = event.getClusterId();
      String hostName = event.getHostName();
  
      if (null == hostName) {
        return;
      }
  
      // invalidate hash and enqueue commands
      m_alertDefinitionHash.get().invalidate(hostName);
      m_alertDefinitionHash.get().enqueueAgentCommands(clusterId,
          Collections.singletonList(hostName));
    }
  
    /**
     * Handles {@link ClusterEvent} by performing the following tasks:
     * <ul>
     * <li>Invalidates all alerts across all hosts. This is because agents use the
     * cluster name as an identifier and if the cluster is renamed, then they need
     * to be rescheduled.</li>
     * </ul>
     *
     * @param event
     *          the event being handled.
     */
    @Subscribe
    @AllowConcurrentEvents
    public void onAmbariEvent(ClusterEvent event) {
      LOG.debug("Received event {}", event);
  
      if( event.getType() != AmbariEventType.CLUSTER_RENAME ) {
        return;
      }
  
  
      AlertDefinitionHash hash = m_alertDefinitionHash.get();
      hash.invalidateAll();
  
      long clusterId = event.getClusterId();
      hash.enqueueAgentCommands(clusterId);
    }
  }
  