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

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 This page provides information about managing nodes in the cluster, including the following topics:

Viewing a List of Nodes

You can view all nodes using the node list command, or view them in the MapR Control System using the following procedure.

To view all nodes using the MapR Control System:

  1. In the Navigation pane, expand the Cluster group and click the Nodes view. 
    The Nodes view contains two panes: the Topology pane and the Nodes pane. The Topology pane shows the racks in the cluster.
  2. Select a rack to display that rack's nodes in the Nodes pane to the right.
  3. Select Cluster to display all the nodes in the cluster.

Clicking any column name sorts data in ascending or descending order by that column.

Selecting the checkbox beside one node makes the following buttons available:

  • Properties - navigates to the Node Properties View, which displays detailed information about a single node.
  • Manage Services - displays the Manage Node Services dialog, which lets you start and stop services on the node.
  • Change Topology - displays the Change Node Topology dialog, which lets you change the topology path for a node.

Formatting Disks on a Node

The disksetup script is used to format disks for use by the MapR cluster. Create a text file /tmp/disks.txt listing the disks and partitions for use by MapR on the node. Each line lists either a single disk or all applicable partitions on a single disk. When listing multiple partitions on a line, separate by spaces. For example:

/dev/sdb
/dev/sdc1 /dev/sdc2 /dev/sdc4
/dev/sdd

Later, when you run disksetup to format the disks, specify the disks.txt file. For example:

/opt/mapr/server/disksetup -F /tmp/disks.txt
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The script disksetup removes all data from the specified disks. Make sure you specify the disks correctly, and that any data you wish to keep has been backed up elsewhere.

If you are re-using a node that was used previously in another cluster, be sure to format the disks to remove any traces of data from the old cluster.

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Run disksetup only after running configure.sh.

Reconfiguring a Node

You can add, upgrade, or remove services on a node to perform a manual software upgrade or to change the roles a node serves. This procedure involves the following steps:

This procedure is designed to make changes to existing MapR software on a machine that has already been set up as a MapR cluster node. If you need to install software for the first time on a machine to create a new node, please see Adding a Node instead.

Stopping the Node

  1. Change to the root user (or use sudo for the following commands).
  2. Stop Warden:
    service mapr-warden stop
  3. If ZooKeeper is installed on the node, stop it:
    service mapr-zookeeper stop

Formatting the Disks (Optional)

If you are re-using a node that was used previously in another cluster, be sure to format the disks by using the disksetup script to remove any traces of data from the old cluster. Refer to the previous section, Formatting Disks on a Node, for instructions.

Installing or Removing Software or Hardware

Before installing or removing software or hardware, stop the node using the procedure described in Stopping the Node.

Once the node is stopped, you can add, upgrade or remove software or hardware. At some point after adding or removing services, you should restart Warden, to re-optimize memory allocation among all the services on the node. It is not crucial to perform this step immediately; you can restart Warden any time when the cluster is not busy.

To add or remove individual MapR packages, use the standard package management commands for your Linux distribution:

  • apt-get (Ubuntu)
  • yum (Red Hat or CentOS)

For information about the packages to install, see Planning the Cluster.

You can add or remove services from a node after it has been deployed in a cluster. This process involves installing or uninstalling packages on the node, and then updating the cluster to recognize the new role for this node.

Adding a service to an existing node:

The process of adding a service to a node is similar to the initial installation process for nodes. For further detail see Installing MapR Software.

  1. Install the package(s) corresponding to the new role(s) using apt-get or yum.
  2. Run configure.sh with a list of the CLDB nodes and ZooKeeper nodes in the cluster.
  3. If you added the CLDB or ZooKeeper role, you must run configure.sh -R on all other nodes in the cluster.
  4. If you added the fileserver role, run disksetup to format and prepare disks for use as storage.
  5. Restart Warden.

When Warden restarts, it picks up the new configuration and starts the new services, making them active in the cluster.

Removing a service from an existing node:

  1. Stop the service you want to remove by using the MapR Control System (MCS) or the maprcli command-line tool. The following example stops the HBase master service:

  2. Purge the service packages with the apt-get, yum, or zypper commands, as suitable for your operating system.
  3. Run the configure.sh script with the -R option.
  4. When you remove the CLDB or ZooKeeper role from a node, run configure.sh -R on all nodes in the cluster.

Configuring the Node

The script configure.sh configures a node to be part of a MapR cluster, or modifies services running on an existing node in the cluster. The script creates (or updates) configuration files related to the cluster and the services running on the node.

Before you run configure.sh, make sure you have a list of the hostnames of the CLDB and ZooKeeper nodes. You can optionally specify the ports for the CLDB and ZooKeeper nodes as well. The default ports are:

Service
Default Port #
CLDB7222
ZooKeeper5181

The script configure.sh takes an optional cluster name and log file, and comma-separated lists of CLDB and ZooKeeper host names or IP addresses (and optionally ports), using the following syntax:

/opt/mapr/server/configure.sh -C <host>[:<port>][,<host>[:<port>]...] -Z <host>[:<port>][,<host>[:<port>]...] [-L <logfile>][-N <cluster name>]
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Each time you specify the -Z <host>[:<port>] option, you must use the same order for the ZooKeeper node list. If you change the order for any node, the ZooKeeper leader election process will fail.

Example:

 

Starting the Node

  1. If ZooKeeper is installed on the node, start it:
    service mapr-zookeeper start
  2. Start Warden:
    service mapr-warden start

 

Renaming a Node

To rename a node:

  1. Stop Warden on the node. Example:

    service mapr-warden stop
  2. If the node is a ZooKeeper node, stop ZooKeeper on the node. Example:

    service mapr-zookeeper stop
  3. Rename the host:
    • On Red Hat or CentOS, edit the HOSTNAME parameter in the file /etc/sysconfig/network and restart the xinetd service or reboot the node.
    • On Ubuntu, change the old hostname to the new hostname in the /etc/hostname and /etc/hosts files.
  4. If the node is a ZooKeeper node or a CLDB node, run configure.sh with a list of CLDB and ZooKeeper nodes.
  5. If the node is a ZooKeeper node, start ZooKeeper on the node. Example:

    service mapr-zookeeper start
  6. Start Warden on the node. Example:

    service mapr-warden start

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