Refinement on MapReduce

https://databricks.com/blog/2015/06/22/understanding-your-spark-application-through-visualization.html

https://spark.apache.org/docs/latest/cluster-overview.html

https://mapr.com/blog/getting-started-spark-web-ui/

https://michalsenkyr.github.io/2018/01/spark-performance

https://dzone.com/articles/my-tryst-with-elasticsearch