We are frequently getting the below error on all datanodes and within some time it is rectifying itself.
Connection failed to http://xxxxxx:8042 (urlopen error timed out)
I checked the port 8042 on the datanode, but it is in Listening state only.
Looks like alert is from NodeManager Health Summary This service-level alert is triggered if there are unhealthy NodeManagers. Can you provide value of property "yarn.nodemanager.health-checker.script.timeout-ms"?