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
019package org.apache.hadoop.yarn.event;
020
021import org.apache.hadoop.classification.InterfaceAudience.Public;
022import 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
032public 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}