https://hadoop.apache.org/docs/r2.7.1/api/org/apache/hadoop/mapred/lib/ChainReducer.html
ChainReducer (Apache Hadoop Main 2.7.1 API)
apache hadoopmainapi
https://hadoop.apache.org/docs/r2.6.1/api/org/apache/hadoop/mapreduce/lib/chain/ChainReducer.html
ChainReducer (Apache Hadoop Main 2.6.1 API)
apache hadoopmainapi
https://hadoop.apache.org/docs/r3.2.0/api/org/apache/hadoop/mapreduce/lib/chain/ChainReducer.html
ChainReducer (Apache Hadoop Main 3.2.0 API)
apache hadoopmainapi