Kubernetes Control Plane
Kubernetes Control Plane is a Kubernetes Component that orchestrates the management of a Kubernetes cluster, ensuring that the desired state of applications is maintained across all worker nodes.
- Context:
- It is a an open-source platform designed to automate the deployment, scaling, and management of containerized applications.
- It can manage the scheduling of pods, cluster-wide resource usage, and handling external/internal requests through its various components.
- It can maintain the desired state of the cluster by continually reconciling it against the configuration specified via the API.
- It can ensure high availability in production environments by distributing control plane components across multiple nodes.
- It includes the following components:
- API Server: The front-end for the Kubernetes control plane that handles communication through REST APIs and the command-line interface.
- etcd: A distributed key-value store that holds the configuration data and state of the cluster, providing the source of truth.
- kube-scheduler: Responsible for assigning pods to nodes based on resource needs, data locality, and workload priorities.
- kube-controller-manager : Aggregates several controllers into a single process to monitor and reconcile the current state with the desired state of resources like nodes and jobs.
- Cloud Controller Manager: Manages cloud-specific resources across various cloud providers via API integrations.
- ...
- Example(s):
- A Kubernetes cluster configured for high availability with multiple control plane nodes running API Server, kube-scheduler, and kube-controller-manager in redundancy, along with etcd for fault tolerance.
- A production-grade cluster where the control plane manages resource distribution by ensuring resource requests and taints/tolerations are met during pod scheduling.
- …
- Counter-Example(s):
- See: Kubernetes Resource Object, Kubernetes Nodes, Kubernetes Pods, Container Orchestration System, Software Development Production Environment.
References
2024a
- (Kubernetes.io, 2024) ⇒ Kubernetes contributors. (2024)."Kubernetes Components.". In: Kubernetes Documentation.
- QUOTE: A Kubernetes cluster consists of a set of worker machines, called nodes, that run containerized applications. Every cluster has at least one worker node.
The worker node(s) host the Pods that are the components of the application workload. The control plane manages the worker nodes and the Pods in the cluster. In production environments, the control plane usually runs across multiple computers and a cluster usually runs multiple nodes, providing fault-tolerance and high availability.
The components of a Kubernetes cluster:
- QUOTE: A Kubernetes cluster consists of a set of worker machines, called nodes, that run containerized applications. Every cluster has at least one worker node.
2024b
- (Harsh, 2024) ⇒ Kumar Harsh (2024). "The Complete Guide to the Kubernetes Control Plane.". In: Loft Blog.
- QUOTE: The Kubernetes control plane is the brain behind a Kubernetes cluster, and it’s responsible for managing the cluster’s state, coordinating operations, and maintaining overall cluster health. There are several components that make up the control plane. These include:
- API server: This is the central component of the control plane that exposes the Kubernetes API. It acts as the entry point for all operational commands and management tasks.
- etcd: This consistent and highly available key-value store is used as the cluster’s primary database. It stores configuration data, state information, and metadata about the cluster.
- Controller manager: This watches the shared state of the cluster through the API server. Also, it ensures that the current state matches the desired state and manages various controllers for nodes, endpoints, replication, and more.
- Scheduler: The scheduler is responsible for assigning nodes to newly created pods based on resource availability and constraints. It also monitors the resource usage of individual nodes and makes decisions about where to deploy new pods.
- Cloud controller manager: This is an optional component of the Kubernetes control plane. It integrates with the cloud provider APIs to manage resources specific to a particular cloud platform, such as load balancers, storage volumes, and networking.
- QUOTE: The Kubernetes control plane is the brain behind a Kubernetes cluster, and it’s responsible for managing the cluster’s state, coordinating operations, and maintaining overall cluster health. There are several components that make up the control plane. These include:
2024c
- (Spot.io, 2024) ⇒ https://spot.io/resources/kubernetes-architecture/11-core-components-explained/ Retrieved: 2024-05-05.
- QUOTE: Kubernetes lets you create, deploy, manage, and scale application containers across one or more host clusters.
A Kubernetes cluster is composed of two separate planes:
- Kubernetes control plane -- manages Kubernetes clusters and the workloads running on them. Include components like the API Server, Scheduler, and Controller Manager.
- Kubernetes data plane -- machines that can run containerized workloads. Each node is managed by the kubelet, an agent that receives commands from the control plane.
- QUOTE: Kubernetes lets you create, deploy, manage, and scale application containers across one or more host clusters.
2024d
- (ARMO, 2024) ⇒ "What is the Kubernetes Control Plane?". In: ARMO Blog. Retrieved: 2024-05-05.
- The Kubernetes control plane manages clusters and resources such as worker nodes and pods. The control plane receives information such as cluster activity, internal and external requests, and more.
Based on these factors, the control plane moves the cluster resources from their current state to the desired state. The Kubernetes Control Plane functions over multiple systems used by a cluster to make an application fault-tolerant while providing high availability for processing requests.
- The Kubernetes control plane manages clusters and resources such as worker nodes and pods. The control plane receives information such as cluster activity, internal and external requests, and more.
2024e
- (ChatGPT-OpenAI, 2024) ⇒ Prompt: Summarize the concept Kubernetes Control Plane in 1- 2 paragraphs. ChatGPT (model:gpt-4-turbo-preview). Retrieved: 2024-05-05.
- QUOTE: The Kubernetes Control Plane is the cornerstone component of Kubernetes, an open-source platform designed to automate the deployment, scaling, and management of containerized applications. It consists of various processes that run either on a single master node or distributed across multiple nodes for high availability. The control plane's primary role is to maintain the desired state of the cluster, as defined by the user through the Kubernetes API. This involves creating and deploying instances, scaling applications up or down, managing changes to existing applications, and orchestrating storage and network resources.
Key components of the Kubernetes Control Plane include the kube-apiserver, which acts as the front end to the control plane; the etcd storage, a reliable distributed data store that persistently stores the cluster's state; the kube-scheduler, which selects which node an unassigned pod should run on; and the kube-controller-manager and cloud-controller-manager, which run controller processes. These components work in tandem to receive, process, and execute requests from users, manage the state of objects within the cluster, and communicate with each other to ensure that the cluster operates as intended, thereby abstracting the complexity of container orchestration from developers and operators.
- QUOTE: The Kubernetes Control Plane is the cornerstone component of Kubernetes, an open-source platform designed to automate the deployment, scaling, and management of containerized applications. It consists of various processes that run either on a single master node or distributed across multiple nodes for high availability. The control plane's primary role is to maintain the desired state of the cluster, as defined by the user through the Kubernetes API. This involves creating and deploying instances, scaling applications up or down, managing changes to existing applications, and orchestrating storage and network resources.
2020b
- (Kubernetes.io, 2020) ⇒ https://kubernetes.io/docs/concepts/overview/kubernetes-api/
- QUOTE: ... The Kubernetes API lets you query and manipulate the state of objects in Kubernetes. The core of Kubernetes' control plane is the API server and the HTTP API that it exposes. Users, the different parts of your cluster, and external components all communicate with one another through the API server.
The core of Kubernetes' control plane is the API server . The API server exposes an HTTP API that lets end users, different parts of your cluster, and external components communicate with one another.
The Kubernetes API lets you query and manipulate the state of objects in the Kubernetes API (for example: Pods, Namespaces, ConfigMaps, and Events).
API endpoints, resource types and samples are described in the API Reference.
- QUOTE: ... The Kubernetes API lets you query and manipulate the state of objects in Kubernetes. The core of Kubernetes' control plane is the API server and the HTTP API that it exposes. Users, the different parts of your cluster, and external components all communicate with one another through the API server.