title: How to handle 'CLUSTERDOWN The cluster is down'? in redis cluster
body: <p>I created a redis cluster with three masters and each one has a single slave like below?
  Master: 127.0.0.1 7000 127.0.0.1 7001 127.0.0.1 7002 
  Slave: 127.0.0.1 7003 127.0.0.1 7004 127.0.0.1 7005 
  Assumption that one master(127.0.0.1 7002) is down and recovered again after a while, why it appears 'CLUSTERDOWN The cluster is down' error message?</p>
  
  <p>Best regards,
  Xu Liang</p>