title: How to maintain a distributed HashMap in Apache Storm Cluster
body: <p>We are having a usecase in Apache Storm , where we need get data from a source system , and then perform some operation on the tuple that is recieved but also want to look up the data in database. But making a Database Call everytime for millions of records is not feasible. 
  So is there a way where we can load a distributed hash map on start up and when the tuple is processed in Bolt or Spout, first lookup this hash map and if the value is not present in the HashMap, then make the Datbase Call and update the corresponding Map which should be accessible across.</p>