Hadoop的ChainMapper.addMapper方法中第二个JobConf参数是什么？

Question

Hadoop的ChainMapper.addMapper，ChainReducer.setReducer和ChainReducer.addMapper方法中第二个JobConf参数是什么？

我认为它只是一个与我正在添加的Mapper或Reducer相关的设置的地方，但是当调用Mapper或Reducer时，我在第二个JobConf上设置的参数不存在。

JobConf overall = new JobConf( Driver.class );
JobConf mapAConf = new JobConf( false );
mapAConf.setInt( "min.word.length", 10 );
ChainMapper.addMapper( overall, Mapper.class, LongWritable.class, Text.class, Text.class, IntWritable.class, false, mapAConf );
ChainReducer.setReducer( overall, Reducer.class, Text.class, IntWritable.class, Text.class, IntWritable.class, false, new JobConf( false ) );

在此示例中，未在mapper类中设置min.word.length值。

提前致谢！