How to build a highly available Linux cluster environment

How to build a highly available Linux cluster environment

Overview:
With the rapid development of the Internet and the growing business needs, high availability has become a modern computing system One of the important goals of design. A Linux cluster environment is a common solution for achieving high availability. This article will introduce how to build a highly available Linux cluster environment and provide detailed code examples.

1. Select the appropriate cluster software
Linux system has a variety of optional cluster software, such as Pacemaker, Keepalived, Heartbeat, etc. When choosing cluster software, you need to consider the following factors:

1. System stability: Choose software that has been used for a long time and has good stability;
2. Community support: Choose a software with active community support and long-term maintenance software;
3. Function richness: choose software with the required functions;
4. Ease of use: choose software that is easy to configure and manage.

2. Install and configure cluster software
Taking Pacemaker as an example, we will introduce its installation and configuration process.

1. Install cluster software:
   Execute the following command on all nodes to install Pacemaker:

   sudo apt-get install pacemaker corosync

2. Configure cluster software:
   Edit corosync configuration file /etc/corosync/corosync.conf, set parameters such as inter-node communication and cluster IP address:

   totem {
    version: 2
    secauth: off
    cluster_name: mycluster
    transport: udpu
   }
   
   nodelist {
    node {
        ring0_addr: <node1_IP>
        nodeid: 1
    }
    node {
        ring0_addr: <node2_IP>
        nodeid: 2
    }
   }
   
   quorum {
    provider: corosync_votequorum
    two_node: 1
   }

Write Pacemaker configuration file /etc/corosync/cib.xml , configure information such as cluster resources and constraints.
For example, create a basic Apache virtual IP resource:

<cib ...>

    <configuration>
        <resources>
            <primitive id="virtual_ip" class="ocf:heartbeat:IPaddr2">
                <instance_attributes ip="192.168.1.100" cidr_netmask="24"/>
                <operations>
                    <op name="monitor" interval="10s"/>
                    <op name="start" interval="0s"/>
                    <op name="stop" interval="0s"/>
                </operations>
            </primitive>
        </resources>
        <constraints>
            <rsc_location rule="1000" score="-INFINITY" id="constraint_virtual_ip"  node="node1"/>
        </constraints>
    </configuration>

</cib>

3. Start the cluster service:
   Execute the following command on all nodes to start the cluster service:

   sudo service corosync start
   sudo service pacemaker start

3. Verify the cluster environment

1. Check the cluster status:
   Execute the following command to check the cluster status:

   sudo crm_mon

   If it is displayed in the output If all nodes are running normally, it means that the cluster environment has been successfully established.

2. Test resource migration:
   Execute the following command to test the resource migration function:

   sudo crm resource migrate virtual_ip node2

   If the resource migration is successful and the virtual IP address is transferred to the node2 node, then Indicates that the resource migration function is normal.

4. Summary
By selecting appropriate cluster software, installing and configuring the cluster software, and verifying the cluster environment, we successfully built a highly available Linux cluster environment. In actual applications, other high-availability resources, such as databases, application services, etc., need to be configured according to specific business needs. Through proper configuration and management, high availability can be ensured and reliable services can be provided.

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