add_nodes.md

Add Nodes (add_nodes.yaml)

add_nodes.yaml is used to add new nodes to an existing Kubernetes cluster, supporting the addition of etcd nodes, worker nodes, or control plane nodes.

Execution Flow

1. Global Initialization

   • Execute the native/root role on all nodes.

2. Pre Install Hook

   • Import and execute pre-installation scripts from hook/pre_install.yaml.

3. Load Defaults and Precheck

   • Load default configurations (defaults) on all nodes.
   • Execute the precheck role to verify that new nodes meet the conditions for joining the cluster.

4. Resource Preparation

   • Execute certs/init on localhost to generate or update certificates.
   • Execute download on localhost to download required software packages and images.

5. Node Initialization

   • Execute the native role for all nodes in the etcd, k8s_cluster, image_registry, and nfs groups to install base packages and configure the system environment.

6. etcd Expansion (external mode only)

   • For nodes in the etcd group, execute in sequence:
     • etcd/prepare
     • etcd/backup
     • etcd/scaling_up/learner
     • etcd/install
     • etcd/scaling_up/promote
     • etcd/postprocess
   • The above steps are triggered only when etcd.deployment_type is external and the node is in the need_installed_etcd list.

7. Sync etcd Config

   • Execute kubernetes/sync-etcd-config on kube_control_plane nodes to sync etcd configuration to the control plane.

8. Container Runtime and Kubernetes Installation

   • For nodes in the k8s_cluster group, execute:
     • cri: Install the container runtime.
     • kubernetes/pre-kubernetes: Install pre-requisites.
     • kubernetes/init-kubernetes: Initialize Kubernetes.
     • kubernetes/join-kubernetes: Join the new node to the cluster (triggered only when the node has not yet loaded Kubernetes services).
     • kubernetes/certs: Distribute or renew certificates (triggered only on control plane nodes when certificate renewal is enabled).
   • The above roles are filtered using the add_nodes list, affecting only nodes that need to be added.