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;
020    
021    import java.io.File;
022    import java.util.LinkedList;
023    import java.util.Queue;
024    
025    import org.apache.hadoop.classification.InterfaceAudience.Public;
026    import org.apache.hadoop.classification.InterfaceStability.Unstable;
027    import org.apache.log4j.FileAppender;
028    import org.apache.log4j.spi.LoggingEvent;
029    
030    /**
031     * A simple log4j-appender for container's logs.
032     * 
033     */
034    @Public
035    @Unstable
036    public class ContainerLogAppender extends FileAppender {
037      private String containerLogDir;
038      //so that log4j can configure it from the configuration(log4j.properties). 
039      private int maxEvents;
040      private Queue<LoggingEvent> tail = null;
041    
042      @Override
043      public void activateOptions() {
044        synchronized (this) {
045          if (maxEvents > 0) {
046            tail = new LinkedList<LoggingEvent>();
047          }
048          setFile(new File(this.containerLogDir, "syslog").toString());
049          setAppend(true);
050          super.activateOptions();
051        }
052      }
053      
054      @Override
055      public void append(LoggingEvent event) {
056        synchronized (this) {
057          if (tail == null) {
058            super.append(event);
059          } else {
060            if (tail.size() >= maxEvents) {
061              tail.remove();
062            }
063            tail.add(event);
064          }
065        }
066      }
067      
068      public void flush() {
069        if (qw != null) {
070          qw.flush();
071        }
072      }
073    
074      @Override
075      public synchronized void close() {
076        if (tail != null) {
077          for(LoggingEvent event: tail) {
078            super.append(event);
079          }
080        }
081        super.close();
082      }
083    
084      /**
085       * Getter/Setter methods for log4j.
086       */
087      
088      public String getContainerLogDir() {
089        return this.containerLogDir;
090      }
091    
092      public void setContainerLogDir(String containerLogDir) {
093        this.containerLogDir = containerLogDir;
094      }
095    
096      private static final int EVENT_SIZE = 100;
097      
098      public long getTotalLogFileSize() {
099        return maxEvents * EVENT_SIZE;
100      }
101    
102      public void setTotalLogFileSize(long logSize) {
103        maxEvents = (int) logSize / EVENT_SIZE;
104      }
105    }