Chukwa is a Hadoop subproject devoted to large-scale log collection and analysis.
Chukwa is built on top of the Hadoop distributed filesystem (HDFS) and MapReduce framework and inherits Hadoop’s scalability and robustness. Chukwa also includes a flexible and powerful toolkit for displaying monitoring and analyzing results, in order to make the best use of this collected data.
Check out the official wiki for more information: http://wiki.apache.org/hadoop/Chukwa