This is documentation for MapR Version 5.0. You can also refer to MapR documentation for the latest release.

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You can add or remove roles to or from a node after deploying the node in a cluster. The process of adding a role to a node involves installing a package on the node, and then, updating the cluster to recognize the new role. The exact procedure depends on the type of role you want to add:

These procedures assume you are adding the role to an existing node.

Adding a Role other than CLDB or ZooKeeper

To add a role other than CLDB or ZooKeeper to an existing node:

  1. Install the package corresponding to the new role using apt-get, yum, or zypper, depending on your platform.
  2. Run configure.sh -R on the node where you added the role.
    Within a short time, if Warden is running at the time you run configure.sh, the new service starts automatically. 
  3. If you added the Fileserver role, run disksetup to format and prepare disks for use as storage.
  4. Restart Warden on the node where you installed the role.

    % service mapr-warden restart 

Restarting Warden

Subsequent sections cover how to add a ZooKeeper or CLDB role that requires restarting Warden. Observe the following best practices when restarting Warden:

  • Perform a rolling restart of Warden to ensure that all services are up.
  • To avoid a failover from occurring, identify nodes running critical services, such as JobTracker or ResourceManager, and restart Warden last on those nodes. 
  • Restart Warden on nodes that run critical cluster services, such as JobTracker or ResourceManager, during periods of low activity.

A rolling restart of Warden means restart Warden on each node, one at a time, pausing until the last restart finishes before beginning the next.

Adding a CLDB Role

To add a CLDB role to a node:

  1. Install the CLDB package corresponding to the new role.
  2. Run configure.sh on the node where you added the new CLDB role. Use the -C option to provide the list of CLDB nodes that includes the new node.
    Within a short time, if warden is running at the time you run configure.sh, the new service starts automatically. 
  3. Run configure.sh on all other nodes in the cluster. Use the -C option and provide the list of CLDB nodes that includes the new node.
  4. Start or restart Warden on the node where you added the CLDB role.
  5. Perform a rolling restart of Warden on all other nodes.
    Warden picks up the new CLDB node.

Adding a ZooKeeper Role

To add a ZooKeeper role to a node:

  1. Install the ZooKeeper package corresponding to the new role.
  2. Run configure.sh on the node where you added the new ZooKeeper role. Use the -Z option to provide the list of ZooKeeper nodes that includes the new node.  
  3. Run configure.sh on all other nodes in the cluster. Use the -Z option to provide the list of ZooKeeper nodes that includes the new node.  
  4. Start or restart ZooKeeper on the node where you added the ZooKeeper role.

    % service mapr-zookeeper restart
     
  5. Perform a rolling restart of ZooKeeper on all other ZooKeeper nodes.
    A rolling restart of ZooKeeper means restart ZooKeeper on each node, one at a time, pausing until the last restart finishes before beginning the next. Restart the ZooKeeper leader last.
  6. Verify that the new node joined the ZooKeeper quorum.

    % service mapr-zookeeper qstatus
     
  7. Perform a rolling restart of Warden on all other nodes.
    Warden picks up the new ZooKeeper node.

If you are increasing the number of ZooKeeper roles in the cluster, for example from one to three ZooKeeper nodes, shut down the cluster before adding the role to the nodes to prevent possible problems. Start the cluster upon completion.

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