001    /**
002    * Licensed to the Apache Software Foundation (ASF) under one
003    * or more contributor license agreements.  See the NOTICE file
004    * distributed with this work for additional information
005    * regarding copyright ownership.  The ASF licenses this file
006    * to you under the Apache License, Version 2.0 (the
007    * "License"); you may not use this file except in compliance
008    * with the License.  You may obtain a copy of the License at
009    *
010    *     http://www.apache.org/licenses/LICENSE-2.0
011    *
012    * Unless required by applicable law or agreed to in writing, software
013    * distributed under the License is distributed on an "AS IS" BASIS,
014    * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015    * See the License for the specific language governing permissions and
016    * limitations under the License.
017    */
018    
019    package org.apache.hadoop.yarn.event;
020    
021    import org.apache.hadoop.classification.InterfaceAudience.Public;
022    import org.apache.hadoop.classification.InterfaceStability.Evolving;
023    
024    /**
025     * Event Dispatcher interface. It dispatches events to registered 
026     * event handlers based on event types.
027     * 
028     */
029    @SuppressWarnings("rawtypes")
030    @Public
031    @Evolving
032    public interface Dispatcher {
033    
034      // Configuration to make sure dispatcher crashes but doesn't do system-exit in
035      // case of errors. By default, it should be false, so that tests are not
036      // affected. For all daemons it should be explicitly set to true so that
037      // daemons can crash instead of hanging around.
038      public static final String DISPATCHER_EXIT_ON_ERROR_KEY =
039          "yarn.dispatcher.exit-on-error";
040    
041      public static final boolean DEFAULT_DISPATCHER_EXIT_ON_ERROR = false;
042    
043      EventHandler getEventHandler();
044    
045      void register(Class<? extends Enum> eventType, EventHandler handler);
046    
047    }