I verified some in my non-production environment.
Then ClusterMaster was broken and hasn't worked, maybe since same time, 2 Indexers have been looked not to be as well.
For recovery I tried some, finally both of Indexers can't show web.
To up web port and service, I put
"#/opt/splunk/bin/splunk set web-port 8000"
Indexer replies
"Couldn't complete HTTP request: Connection reset by peer"
I tried to reboot platform and restart Splunk service and so on, but this isn't resolved.
Please help.
