Hadoop

Add a new node to an existing cluster

This task’s steps are as same as the steps involved in installing CDH but the scenario is different, as we’re adding hosts to an existing cluster.

Once the cluster is setup and running, you may have the requirement for adding new nodes to the cluster.

To do that, ensure initial OS configurations/prechecks are complete.

Go to CM – Hosts

Select Add New Hosts to Cluster – give the hosts hostname/ip – continue

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Now we have encountered an error in the step of installing java/cm agent and heartbeat to host.

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Whenever you encounter an error message like this, click the details and go through the logs to identify the cause.

In this case, I didn’t properly update the /etc/hosts section of the hosts, so host didn’t identify the master host and thus failed.

After correcting the /etc/hosts information of slave2 and given retry,

CDH installation

Here we’ve got a warning in the hostname checks.

Upon clicking the warning, it says DNS lookup of slave2 failed in slave1 and standby.

This is caused by due to lack of update of the slave2 hosts information in the /etc/hosts file of standy and slave1.

Now I updated the /etc/hosts in standby and slave1.

Each server be able to identify the other hosts in the cluster.

Now reran the hosts inspector,

Host template:

Hosts template is nothing but a template win which you’re defining what are the roles and services to be applied to the newly added hosts.

It will be helpful when you’re adding multiple hosts and looking to assign same services/roles in all the hosts.

Since we don’t have any, I’m creating a new template.

The host template can be created at any time in the Cm – Hosts – hosts template section.

I’ve skipped the host template and assigning roles to the services.

Now, the server will be listed in the hosts section without any services/roles running on it.

To add a service/assign role on the hosts, go to any service – instances – add role instances – select slave2.

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Finish

Problem Scenarios:

· Add the given node to the existing cluster and add specific services/roles in it.

· Create a host template with given services/roles details and add a new host, apply the host template.

· Your colleague facing an error while adding a new host in the cluster, troubleshoot the errors and add the host.

· Run the hosts inspector on the hosts and resolve the warnings/errors.

Thus we covered how to Add a new node to an existing cluster

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