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Basic Cluster Information

Kubernetes is an open source container orchestration engine for automating deployment, scaling, and management of containerized applications.

For developers, Kubernetes is a cluster operating system. Kubernetes provides service discovery, scaling, load balancing, self-healing, and even leader election, freeing developers from infrastructure-related configurations.

When using Kubernetes, it is like you run a large number of servers as one and the method for deploying applications in Kubernetes is always the same.

Kubernetes Cluster Architecture

A Kubernetes cluster consists of master nodes (Masters) and worker nodes (Nodes). Applications are deployed on worker nodes, and you can specify the nodes for deployment.

Note

For a cluster created on CCE, the master node is hosted by CCE. You only need to create a node.

The following figure shows the architecture of a Kubernetes cluster.

Figure 1 Kubernetes cluster architecture

Master node

A master node is the machine where the control plane components run, including API server, Scheduler, Controller manager, and etcd.

  • API server: functions as a transit station for components to communicate with each other, receives external requests, and writes information to etcd.
  • Controller manager: performs cluster-level functions, such as component replication, node tracing, and node fault fixing.
  • Scheduler: schedules containers to nodes based on various conditions (such as available resources and node affinity).
  • etcd: serves as a distributed data storage component that stores cluster configuration information.

In a production environment, multiple master nodes are deployed to ensure high cluster availability. For example, you can deploy three master nodes for your CCE cluster.

Worker node

A worker node is a compute node in a cluster, that is, a node running containerized applications. A worker node has the following components:

  • kubelet: communicates with the container runtime, interacts with the API server, and manages containers on the node.
  • kube-proxy: serves as an access proxy between application components.
  • Container runtime: functions as the software for running containers. You can download images to build your container runtime, such as Docker.

Master Nodes and Cluster Scale

When you create a cluster on CCE, you can have one or three master nodes. Three master nodes can create a cluster in HA mode.

The master node specifications decide the number of nodes that can be managed by a cluster. You can select the cluster management scale, for example, 50 or 200 nodes.

Cluster Network

From the perspective of the network, all nodes in a cluster are located in a VPC, and containers are running on the nodes. You need to configure node-node, node-container, and container-container communication.

A cluster network can be divided into three network types:

  • Node network: IP addresses are assigned to nodes in a cluster.
  • Container network: IP addresses are assigned to containers in a cluster for communication. Currently, multiple container network models are supported, and each model has its own working mechanism.
  • Service network: A Service is a Kubernetes object used to access containers. Each Service has a fixed IP address.

When you create a cluster, select a proper CIDR block for each network. Ensure that the CIDR blocks do not conflict with each other and have sufficient available IP addresses. You cannot change the container network model after the cluster is created. Plan the container network model properly in advance.

You are advised to learn about the cluster network and container network models before creating a cluster. For details, see Container Network Models <cce_10_0280>.

Cluster Lifecycle

Table 1 Cluster status
Status Description
Creating A cluster is being created and is requesting for cloud resources.
Running A cluster is running properly.
Scaling-out A node is being added to a cluster.
Scaling-in A node is being deleted from a cluster.
Hibernating A cluster is hibernating.
Awaking A cluster is being woken up.
Upgrading A cluster is being upgraded.
Unavailable A cluster is unavailable.
Deleting A cluster is being deleted.