5. Decommissioning Masters and Slaves
Decommissioning is a process that supports removing a component from the cluster. You must decommission a master or slave running on a host before removing the component or host from service. Decommissioning helps prevent potential loss of data or service disruption. Decommissioning is available for the following component types:
DataNodes
NodeManagers
RegionServers
Decommissioning executes the following tasks:
For DataNodes, safely replicates the HDFS data to other DataNodes in the cluster.
For NodeManagers, stops accepting new job requests from the masters and stops the component.
For RegionServers, turns on drain mode and stops the component.