Components of Manager and Worker Nodes

Let’s learn about the components of manager and worker nodes in Kubernetes’ architecture and explore the concurrency control mechanism in Kubernetes.

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Components of the manager node

The main components of the manager node are the API Server (kube-apiserver), the Scheduler (kube-scheduler), and the Controller Manager (kube-controller-manager).

The API Server (kube-apiserver)

The API Server is the front-end of the Kubernetes cluster, allowing users to inspect the resources of the cluster and modify them or create new ones.

The Scheduler (kube-scheduler)

The Scheduler detects newly created pods that have no nodes assigned and selects a node for them to run.

Note that this selection of Scheduler is based on multiple criteria, such as user-specified constraints, affinity specifications, data locality, etc.

The Controller Manager (kube-controller-manager)

The Controller Manager runs all the available controllers in the manager node. A controller is a control loop that watches the state of the cluster through the API server making changes in order to move the current state towards the desired state

Below are some examples of controllers:

  • Node Controller: responsible for noticing and responding to node failures
  • Replication Controller: responsible for maintaining the correct number pods according to the replication specified by the user.
  • Endpoints Controller: responsible for creating endpoints for services.

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