title: Merging small files into single file in hdfs
body: <p>In a cluster of hdfs, i receive multiple files on a daily basis which can be of 3 types :</p>
  
  <p><strong>1)</strong> product_info_timestamp</p>
  
  <p><strong>2)</strong> user_info_timestamp</p>
  
  <p><strong>3)</strong> user_activity_timestamp</p>
  
  <p>The number of files received can be of any number but they will belong to one of these 3 categories only. </p>
  
  <p>I want to merge all the files(after checking whether they are less than 100mb) belonging to one category into a single file.
  for eg: 3 files named product_info_* should be merged into one file named product_info.</p>
  
  <p>How do i achieve this?</p>