Thursday, 12 January 2012

RedHat Cluster Suite and Conga - Linux Clustering

This how to describes an easy step by step installation of the Red Hat Cluster Suite on 3 centos nodes and prepare them as nodes of a cluster. You will also install the Management suite which is web based and is known as Conga.

You will use 3 nodes to form the cluster and 1 node as the cluster management node and as a cluster node it will not take part. All the nodes and the management node should be resolvable either by host file entries or by DNS.

Cluster Nodes:
cnode1:
    eth0-192.168.2.151/24 - external-lan
    eth1-192.168.1.200/26 - internal-lan cluster
    eth2-192.168.200.1/26 - internal-iscsi-san lan
cnode2:
    eth0-192.168.2.152/24 - external-lan
    eth1-192.168.1.201/26 - internal-lan cluster
    eth2-192.168.200.2/26 - internal-iscsi-san lan
cnode3:
    eth0-192.168.2.153/24 - external-lan
    eth1-192.168.1.202/26 - internal-lan cluster
    eth2-192.168.200.3/26 - internal-iscsi-san lan

Cluster Management Node:
centos:
    eth0-192.168.2.150/24

As the cluster, its management interface and the service deamons use tcp, for the purpose of this article you can disable the firewalls at these nodes.

OS - All Nodes:
    CentOS 6 Minimal
   
Cluster Nodes - Software Installation:
    yum groupinstall "High Availability"
    yum install ricci
   
Cluster Management Node - Software Installation:
    yum groupinstall "High Availability Management"
    yum install ricci

Copy this initial sample cluster config file into /etc/cluster/cluster.conf at all the nodes cnode1, cnode2, cnode3.
<?xml version="1.0"?>
<cluster config_version="1" name="cl1">
    <clusternodes>
        <clusternode name="cnode1" nodeid="1"/>
        <clusternode name="cnode2" nodeid="2"/>
        <clusternode name="cnode3" nodeid="3"/>
    </clusternodes>
</cluster>

This initial file states that the cluster name is 'cl1' and defines the cluster nodes.

Now some services have to be configured and started at the nodes first and then at the management node as below.

Cluster Nodes:
    chkconfig iptables off
    chkconfig ip6tables off
    chkconfig ricci on
    chkconfig cman on
    chkconfig rgmanager on
    chkconfig modclusterd on

    create a password for the ricci service user with 'passwd ricci'
   
    service iptables stop
    service ip6tables stop
    service ricci start
    service cman start
    service rgmanager start
    service modclusterd start

Cluster Management Node:
    chkconfig iptables off
    chkconfig ip6tables off
    chkconfig luci on
    chkconfig ricci on

    service iptables stop
    service ip6tables stop
    service luci start
    service ricci start

luci service is the management service that presents the web based cluster interface via https at port 8084 and can be accessed in any browser at https://<cluster management node FQDN or hostname:8084>/

ricci service is the under laying deamon that helps in cluster configuration sync and file copy, service start, stop etc. and uses tcp port 11111.

luci : 8084
ricci : 11111

cman, rgmanager and modclusterd are the actual cluster services which futher start other services that actually make the clustering happenand keep it live.

Open a browser and enter the conga node url which in this case is https://centos:8084/


After clicking 'ok' to the initial warning information you will be presented with the login screen. Enter the root user and root password of that system and start the interface.

Now click Add cluster and add the first node cnode1 and the ricci password, click ok and it will detect the other two nodes also, add the ricci passwords and the cluster will be added to the Cluster Management interface.


The cluster can now be managed and configured from this interface.


Care should be take as the cluster.conf file sometimes does not get synced to all cluster nodes they will get fenced due to version misconfiguration. At such times copy the cluster.conf file from node1 to all the other nodes.


If all the nodes are in sync then the up time is shown in the cluster nodes list.

Getting a cluster, configuring and managing, your cluster is up, live and configured in no time and later other clusters can be added into this management interface for easy maintenance.

- Bellamkonda Sudhakar

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