Message in mapreduce class not logged

[Thomas Anderson]

I have setup a cluster with several machines up and running. But I
encounter a problem that my mapper reducer class does not log.

The hadoop version I use is 0.20.2. The rootLogger in log4j.properties
adds DRFA (daily rolling file appender) and RFA (rolling file
appender).

My map reduce class looks as below

public class MyTest{
        public static final Log LOG = LogFactory.getLog(MyTest.class);

        public static class MiniMap extends Mapper<LongWritable, Text,
Text, Text>{
                private long count = 0;
                public void map(LongWritable key, Text value,
Mapper.Context ctx) throws IOException, InterruptedException{
                        String valueString = value.toString();
LOG.info("XXXXXXXXXXX value string obtained: "+valueString);
                        ctx.write(new LongWritable(counter++),
doSomething(valueString));
                }

        }
...
        static String fetch(String urlpath){
          ...
LOG.info("xxxxxxxxxxxxxx");
           ...
        }
}

The error shows 0java.lang.NullPointerException

    [java]      at 
org.apache.hadoop.mapred.MapTask$MapOutputBuffer.collect(MapTask.java:849)
     [java]     at
org.apache.hadoop.mapred.MapTask$NewOutputCollector.write(MapTask.java:541)
     [java]     at
org.apache.hadoop.mapreduce.TaskInputOutputContext.write(TaskInputOutputContext.java:80)
     [java]     at myapp.MyTest.$MiniMap.map(MiniMap.java:51)
     [java]     at myapp.MyTest.$MiniMap.map(MiniMap.java:44)

The error message points out the line that goes wrong, but the problem
is I do not see any message (in LOG.info(...)) get logged.

What else I need to turn on or modify so that log message can be seen
in e.g. hadoop/logs/hadoop-...log?

I appreciate any suggestion.