What is Kubernetes Master Node?

In Kubernetes, the master node is the central component responsible for managing the Kubernetes cluster. It orchestrates and controls the various worker nodes that run your applications and services. The master node performs several key functions, including:

Key Responsibilities of the Master Node:

  1. API Server (kube-apiserver): The API server is the front-end of the Kubernetes control plane. It exposes the Kubernetes API, and all communication with the cluster (e.g., from the command-line kubectl tool or other components) happens via this API. It validates and processes REST requests and updates the cluster state in the etcd database.

  2. Scheduler (kube-scheduler): The scheduler is responsible for placing or scheduling pods onto worker nodes based on various factors, such as resource availability, affinity/anti-affinity rules, taints, and tolerations.

  3. Controller Manager (kube-controller-manager): The controller manager is a set of controllers that regulate the state of the cluster. Controllers work to ensure that the desired state of the system is maintained. For example, the replication controller ensures that the correct number of pod replicas are running, and the deployment controller ensures that new deployments roll out properly.

  4. etcd: etcd is a distributed key-value store used to store all cluster data, including configuration data, secrets, and the current state of all objects in the cluster. The API server reads from and writes to etcd to maintain the state of the system.

  5. Cloud Controller Manager: If the Kubernetes cluster is running on a cloud provider, this component interacts with the provider's API to manage resources like load balancers, networking, and storage. This component is typically optional and only used in cloud-based clusters.

Why monitor Kubernetes Master Node?

Monitoring the Kubernetes master node is crucial because it manages the entire cluster's state and functionality. If the master node fails or encounters issues, the entire cluster can become unresponsive, affecting application availability and performance. Key components like the API server, scheduler, and controller manager rely on constant monitoring to ensure they're running smoothly. By tracking resource usage, error logs, and health metrics, you can proactively identify bottlenecks, prevent downtime, and ensure the control plane is operating optimally, maintaining cluster stability and reliability for all workloads and services in the system.

eG Enterprise provides a specialized monitoring model for monitoring Kubernetes Master Node.