Overview

Introduction

Installing the ESB3027 AgileTV CDN Manager for production requires a minimum of three nodes. More details about node roles and sizing can be found in the System Requirements Guide. Before beginning the installation, select one node as the primary “Server” node. This node will serve as the main installation point. Once additional Server nodes join the cluster, all Server nodes are considered equivalent, and cluster operations can be managed from any of them. The typical process involves installing the primary node as a Server, then adding more Server nodes to expand the cluster, followed by joining Agent nodes as needed to increase capacity.

Air-Gapped Environments

In air-gapped environments—those without direct Internet access—additional considerations are required. First, on each node, the Operating System’s ISO must be mounted so that dnf can be used to install essential packages included with the OS. Second, the “Extras” ISO from the ESB3027 AgileTV CDN Manager must be mounted to provide access to container images for third-party software that would otherwise be downloaded from public repositories. Details on mounting this ISO and loading the included images are provided below.

Roles

All nodes in the cluster have one of two roles. Server nodes run the control-plane software necessary to manage the cluster and provide redundancy. Agent nodes do not run the control-plane software; instead, they are responsible for running the Pods that make up the applications. Jobs are distributed among agent nodes to enable horizontal scalability of workloads. However, agent nodes do not contribute to the cluster’s high availability. If an agent node fails, the Pods assigned to that node are automatically moved to another node, provided sufficient resources are available.

Control-plane only Server nodes

Both server nodes and agent nodes run workloads within the cluster. However, a special attribute called the “CriticalAddonsOnly” taint can be applied to server nodes. This taint prevents the node from scheduling workloads that are not part of the control plane. If the hardware allows, it is recommended to apply this taint to server nodes to separate their responsibilities. Doing so helps prevent misbehaving applications from negatively impacting the overall health of the cluster.

graph TD
    subgraph Cluster
        direction TB
        ServerNodes[Server Nodes]
        AgentNodes[Agent Nodes]
    end

    ServerNodes -->|Manage cluster and control plane| ControlPlane
    ServerNodes -->|Provide redundancy| Redundancy

    AgentNodes -->|Run application Pods| Pods
    Pods -->|Handle workload distribution| Workloads
    AgentNodes -->|Failover: Pods move if node fails| Pods

    ServerNodes -->|Can run Pods unless tainted with CriticalAddonsOnly| PodExecution
    Taint[CriticalAddonsOnly Taint] -->|Applied to server nodes to restrict workload| ServerNodes

For high availability, at least three nodes running the control plane are required, along with at least three nodes running workloads. These can be a combination of server and agent roles, provided that the control-plane nodes are sufficient. If a server node has the “CriticalAddonsOnly” taint applied, an additional agent node must be deployed to ensure workloads can run. For example, the cluster could consist of three untainted server nodes, or two untainted servers, one tainted server, and one agent, or three tainted servers and three agents—all while maintaining at least three control-plane nodes and three workload nodes.

The “CriticalAddonsOnly” taint can be applied to server nodes at any time after cluster installation. However, it only affects Pods scheduled in the future. Existing Pods that have already been assigned to a server node will remain there until they are recreated or rescheduled due to an external event.

kubectl taint nodes <node-name> CriticalAddonsOnly=true:NoSchedule

Where node-name is the hostname of the node for which to apply the taint. Multiple node names may be specified in the same command. This command should only be run from one of the server nodes.

Next Steps

Continue reading the Installation Requirements.