High Availability Group

In the Load Balancing service, you can use the High Availability Group feature to ensure high availability. This feature bundles Application Load Balancer (ALB), Network Load Balancer (NLB), and Direct Server Return Network Load Balancer (DSRNLB) nodes—which were previously created for each availability zone—into a single unit to guarantee high availability.

Basic concepts

Describes the components and related concepts that make up a High Availability Group.

Load balancer node

This refers to all types of load balancer resources (ALB, NLB, DSRNLB) created via the KakaoCloud Console > Beyond Networking Service > Load Balancing > Load Balancer menu. Only load balancer nodes that match the scheme and type specified when creating a High Availability Group can be connected. By connecting load balancer nodes with identical settings and types from different availability zones to the same High Availability Group, you can ensure the high availability of the load balancer.

While a load balancer node can perform basic load balancing functions on its own, it is recommended for applications requiring high availability to connect two or more load balancer nodes with the same settings and types, each created in different availability zones, to a High Availability Group.

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• A High Availability Group can be created with at least one load balancer node connected, but high availability is not guaranteed in this case.
• If a load balancer node is connected to a High Availability Group, you cannot perform public IP connection/disconnection tasks or delete the load balancer.

High Availability Group

A High Availability Group is a resource that ensures high availability by grouping two or more load balancer nodes of the same settings and type created in different availability zones.

When creating a High Availability Group, you select the scheme, type, and VPC. By connecting two or more load balancer nodes from different availability zones that meet these criteria, you can guarantee high availability. The concepts related to a High Availability Group are as follows:

• Scheme: You can choose between Internet-facing, which allows communication with the outside via the Internet, and Internal, which allows communication within a private subnet.
• Type: Specifies the type of load balancer nodes to connect. You can select one from ALB, NLB, or DSRNLB.

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• A High Availability Group can be configured with at least one load balancer node connected, but it is recommended to connect two or more to ensure high availability.

Status

The status of a High Availability Group is divided into provisioning status and operating status. Detailed descriptions of each status are as follows:

Provisioning status

Status	Description
Active	Provisioning has been successfully completed
Creating	The High Availability Group is being created
Updating	The High Availability Group is being updated
Deleting	The High Availability Group is being deleted
Error	Provisioning has failed

Operating status

Status	Description
Online	The High Availability Group is operating normally, and the operating status of all connected load balancer nodes is Online
Degraded	Some listeners of the load balancer nodes connected to the High Availability Group are in an Error state, or some targets within the target group connected to the load balancer nodes are in an Error state
Error	Some listeners of the load balancer nodes connected to the High Availability Group are in an Error state

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If the operating status of the High Availability Group is Error, please check if the following settings are correct:

• Verify that security groups are correctly configured for each target instance of the load balancer nodes connected to the High Availability Group, and that each target can send and receive packets.
• Verify that health check settings are correctly configured in the target groups of each load balancer node connected to the High Availability Group.

Requirements

To ensure high availability of load balancers through a High Availability Group, the following requirements must be met:

• At least two load balancer nodes created in different availability zones must be connected to the High Availability Group.
• Each load balancer node connected to the High Availability Group must have the same scheme, type, and VPC as the values set in the High Availability Group.
• The detailed settings of each load balancer node connected to the High Availability Group must be identical. This includes settings such as listener properties, maximum connection settings, and protocols.
• The provisioning status of each load balancer node connected to the High Availability Group must be Active.