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.io.Flushable;
023    import java.util.LinkedList;
024    import java.util.Queue;
025    
026    import org.apache.hadoop.classification.InterfaceAudience.Public;
027    import org.apache.hadoop.classification.InterfaceStability.Unstable;
028    import org.apache.log4j.FileAppender;
029    import org.apache.log4j.spi.LoggingEvent;
030    
031    /**
032     * A simple log4j-appender for container's logs.
033     * 
034     */
035    @Public
036    @Unstable
037    public class ContainerLogAppender extends FileAppender
038      implements Flushable
039    {
040      private String containerLogDir;
041      //so that log4j can configure it from the configuration(log4j.properties). 
042      private int maxEvents;
043      private Queue<LoggingEvent> tail = null;
044    
045      @Override
046      public void activateOptions() {
047        synchronized (this) {
048          if (maxEvents > 0) {
049            tail = new LinkedList<LoggingEvent>();
050          }
051          setFile(new File(this.containerLogDir, "syslog").toString());
052          setAppend(true);
053          super.activateOptions();
054        }
055      }
056      
057      @Override
058      public void append(LoggingEvent event) {
059        synchronized (this) {
060          if (tail == null) {
061            super.append(event);
062          } else {
063            if (tail.size() >= maxEvents) {
064              tail.remove();
065            }
066            tail.add(event);
067          }
068        }
069      }
070      
071      @Override
072      public void flush() {
073        if (qw != null) {
074          qw.flush();
075        }
076      }
077    
078      @Override
079      public synchronized void close() {
080        if (tail != null) {
081          for(LoggingEvent event: tail) {
082            super.append(event);
083          }
084        }
085        super.close();
086      }
087    
088      /**
089       * Getter/Setter methods for log4j.
090       */
091      
092      public String getContainerLogDir() {
093        return this.containerLogDir;
094      }
095    
096      public void setContainerLogDir(String containerLogDir) {
097        this.containerLogDir = containerLogDir;
098      }
099    
100      private static final int EVENT_SIZE = 100;
101      
102      public long getTotalLogFileSize() {
103        return maxEvents * EVENT_SIZE;
104      }
105    
106      public void setTotalLogFileSize(long logSize) {
107        maxEvents = (int) logSize / EVENT_SIZE;
108      }
109    }