Question-86: What is the use of Ambari Dashboard UI?

Answer: If you wanted to check the History of the Cluster then you would be using the Dashboard. Which provides the information like Metrics, and visualization in the form of Heat Map, what all parameters have changed for the cluster configurations.

Question-87: What is the use of Ambari Web Host pages?

Answer: Ambari Web Hosts is a web page in the Ambari Web UI and that can be used to manage the multiple components like DataNodes, NameNodes, NodeManager, RegionServers etc Using this UI can start specific component or can do the rolling restarts.

Question-88: On the Host page you see black, medical bag icon against one host. What does that mean?

Answer: It means host in the maintenance mode.

Question-89: What do you mean by decommissioning a host from the cluster?

Answer: Decommissioning is a process which supports the removing components and their hosts from the cluster.

Question-90: Are there any specific steps we need to follow for decommissioning host from the cluster?

Answer: We need to first decommission the master or slave which are running before removing host from the cluster. Decommissioning is only available for the following

When you do the decommissioning required operations are already been taken care by the decommissioning process.

• DataNode : It make sure that data from the decommissioned node safely replicated to the other nodes in the cluster.
• NodeManagers: During the decommissioning it would stop accepting the new job requests and stops the components.
• RegionServers (To understand it more check the HBase training) : It goes into drain mode and stops the components.