Control plane

As explained in Kubernetes in Action, Second Edition

A control plane is the cluster-management component that makes decisions about and controls the operation of worker resources.

A control plane is the brain of a Kubernetes cluster: it controls worker resources and provides one Kubernetes API for deploying applications across the cluster. Worker nodes run the applications; control plane nodes manage them. section 1.2.1

The control plane coordinates the cluster through several components:

• The Kubernetes API Server exposes the RESTful API through which engineers and other components create objects. section 1.2.3
• etcd persists objects created through the API; the API Server is the only component that communicates with it. section 1.2.3
• The Scheduler selects a worker node for each application instance. section 1.2.3
• Controllers bring API-created objects to life, sometimes communicating with external systems such as a cloud provider. section 1.2.3

Control plane components hold and control cluster state but do not run applications. They can run on one node in a non-production cluster or be replicated across multiple nodes for high availability; highly available clusters use at least three physical control plane nodes. section 1.2.1 section 1.2.3

Figure 1.12 The components of the Kubernetes control plane

Use the control-plane component diagram to connect the API Server, etcd, Scheduler, and controllers with their cluster-management roles. section 1.2.3

How Kubernetes in Action, Second Edition covers it

How deep it goes

Defines the control plane, identifies its components and roles, and stops short of detailed component internals.

Examples

Uses control-versus-workload planes, a uniform deployment area, and API Server, etcd, Scheduler, and controller roles.

What it assumes

Introduces control planes, worker nodes, and their relationship without requiring prior cluster-component knowledge.

What you can do after

Evaluate Kubernetes cluster architecture by distinguishing management components from worker-node application execution.

How it connects

Connects control planes with worker nodes, the Kubernetes API, API Server, etcd, Scheduler, controllers, and high availability.

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Also explained in

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  Effective Platform EngineeringThe control plane is the part of a distributed system that manages configuration, coordination, and lifecycle decisions for system resources.
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  Acing the CCNA Exam: Volume 2 Advanced Networking and SecurityThe control plane is the set of network-device functions that determines the rules and state used by the data plane to forward traffic.
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  Kafka for ArchitectsA service-mesh control plane is the centralized subsystem that configures, deploys, and manages the behavior of sidecar proxies and mesh-wide network policies.
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  Azure SecurityA control plane action operates on the configuration or management of an Azure resource rather than on data stored within it.
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  Learn Docker in a Month of Lunches, Second EditionA Kubernetes control plane is the set of management components that maintain cluster state and coordinate workloads.
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  Cloud Observability in ActionThe Kubernetes control plane is the set of Kubernetes components that expose the cluster API and maintain the desired state of cluster resources.
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  Authorization in ActionA control plane is the set of interfaces and mechanisms used to define, configure, govern, and manage a system's behavior and infrastructure.

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Related concepts

• service meshpart of · A service mesh is an infrastructure layer that manages communication and cross-cutting concerns such as traffic control, security, and observability between distributed services.
• data planecontrasts with · A data plane is the part of a networked or distributed system that executes workloads and carries or processes application data and traffic.
• Kubernetespart of · Kubernetes is an open-source platform for orchestrating and automating the deployment, scaling, and management of containerized workloads across computing clusters.
• kubernetes api serverhas part · The Kubernetes API server is the control-plane component that exposes, validates, and processes the Kubernetes API for managing cluster resources and state.
• rate limitconfigures · A rate limit is a bound on the frequency or volume of operations permitted within a defined interval, scope, or concurrency limit.

This explainer was generated by Manning's knowledge graph from the text of Kubernetes in Action, Second Edition. The section links point to the parts of the book it draws on.