title: how to change spark.r.backendConnectionTimeout value?
body: <p>When I use R in Zeppelin it works but when I leave the Zeppelin running one day, next day I get this error for R only: </p>
  
  <blockquote>
    <p>sparkR backend is dead, please try to increase spark.r.backendConnectionTimeout</p>
  </blockquote>
  
  <p>I see from the Spark <a href="https://spark.apache.org/docs/latest/configuration.html#sparkr" rel="nofollow noreferrer">configuration</a> that default value is set to 6000 seconds. Does anybody know how to change this value and what value would be useful to keep Zeppelin running all the time? I can use other interpreters (Python, Jdbc, etc.) without having this problem.</p>