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.service; 020 021import org.apache.commons.logging.Log; 022import org.apache.commons.logging.LogFactory; 023import org.apache.hadoop.classification.InterfaceAudience.Public; 024import org.apache.hadoop.classification.InterfaceStability.Evolving; 025 026/** 027 * This is a state change listener that logs events at INFO level 028 */ 029@Public 030@Evolving 031public class LoggingStateChangeListener implements ServiceStateChangeListener { 032 033 private static final Log LOG = LogFactory.getLog(LoggingStateChangeListener.class); 034 035 private final Log log; 036 037 /** 038 * Log events to the given log 039 * @param log destination for events 040 */ 041 public LoggingStateChangeListener(Log log) { 042 //force an NPE if a null log came in 043 log.isDebugEnabled(); 044 this.log = log; 045 } 046 047 /** 048 * Log events to the static log for this class 049 */ 050 public LoggingStateChangeListener() { 051 this(LOG); 052 } 053 054 /** 055 * Callback for a state change event: log it 056 * @param service the service that has changed. 057 */ 058 @Override 059 public void stateChanged(Service service) { 060 log.info("Entry to state " + service.getServiceState() 061 + " for " + service.getName()); 062 } 063}