https://community.cloudera.com/t5/Support-Questions/NiFi-node-keeps-disconnecting-from-the-cluster/m-p/191891#M153970 <P>Hi Matt,</P><P>I tried exactly what you suggested while I was waiting for your reply. I was able to access the UI without the data flow running. I looked at the System Diagnostics you mentioned earlier. It was "4 times" without data flow running and still "8 times" now after I started data flows. </P><P>Our cluster has 2-node and each has 16 cores. The "max timer driven thread count" is set to 64 and "max event driven thread count" is set to 12. I've been monitoring "top", cpu usage at this time (busy hour) is about 700%. </P><P>Good news is after I started nifi in stopped state and manually restarted the data flows, the problem I had this morning has not recurred yet. Heartbeats are generated in reasonable intervals - about 7 seconds. What happened this morning is still a mystry to me, but I am happy now it's working.</P><P>Thank you so much for all the help!!!</P><P>Xi</P> Wed, 31 May 2017 01:45:01 GMT xsanderson 2017-05-31T01:45:01Z