Go to ResourceManager UI on Ambari. Click
nodes link on the left side of the window. It should show all Node
Managers and the reason for it being listed as unhealthy. Mostly found reasons are regarding disk space threshold
reached. In that case needs to consider following parameters
Parameters
Default value
Description
yarn.nodemanager.disk-health-checker.min-healthy-disks
0.25
The minimum fraction of number of disks to be healthy for the
node manager to launch new containers. This correspond to both
yarn.nodemanager.local-dirs and yarn.nodemanager.log-dirs. i.e. If there are
less number of healthy local-dirs (or log-dirs) available, then new
containers will not be launched on this node.
yarn.nodemanager.disk-health-checker.max-disk-utilization-per-disk-percentage
90.0
The maximum percentage of disk space utilization allowed after
which a disk is marked as bad. Values can range from 0.0 to 100.0. If the
value is greater than or equal to 100, the nodemanager will check for full
disk. This applies to yarn.nodemanager.local-dirs and
yarn.nodemanager.log-dirs.
yarn.nodemanager.disk-health-checker.min-free-space-per-disk-mb
0
The minimum space that must be available on a disk for it to
be used. This applies to yarn.nodemanager.local-dirs and
yarn.nodemanager.log-dirs.
In the final step, if above steps do not reveal the actual
problem , needs to check log , location path : /var/log/hadoop-yarn/yarn.
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