What is observed:
On my currently active YARN NodeManager and ResourceManager, Ambari
alerts are fine.
On the secondary YARN NodeManager and ResourceManager, Ambari reports
"Status: Unknown" / "HTTP 200 response (metrics unavailable)". This
is for the alerts:
- NodeManager Health Summary
- ResourceManager CPU Utilization
- ResourceManager RPC Latency
The Ambari web interface does not make this error obvious, as it says
"0 alerts" in the top bar. But you can see the alerts with "unknown"
status when you go to the ambari alerts page, or if you query the
What is expected:
Ambari alerts does not generate any alarms on a secondary YARN HA node as long as the node is responsive.
A network dump of the ambari poll against the secondary RM looks like:
GET /jmx?qry=Hadoop:service=ResourceManager,name=RMNMInfo HTTP/1.1
HTTP/1.1 200 OK
Refresh: 3; url=http://
This is standby RM. Redirecting to the current active RM:
I'm also filing a JIRA against YARN (per request from jhurley) and will post that info here.
Comment from Jonathan Hurley email@example.com:
1) There should be a ticket filed for YARN to have their HA mode use a proper redirect
2) Ambari might not want to produce an UNKNOWN response here since it gives a false feeling that something went wrong.