Kubernetes cluster concepts

Category : Kubernetes | Sub Category : Kubernetes With Java | By Prasad Bonam Last updated: 2023-11-21 10:50:34 Viewed : 217

A Kubernetes cluster is a set of physical or virtual machines (nodes) that run containerized applications orchestrated by Kubernetes. Here are some key concepts related to Kubernetes clusters:

1. Nodes:

• Nodes are the individual machines (physical or virtual) in the cluster where containers are deployed.
• Each node runs a container runtime (like Docker) and has the necessary Kubernetes components (kubelet and kube-proxy) to communicate with the master.

2. Master:

• The master node is responsible for managing the overall state of the cluster.
• It schedules applications, maintains the desired state, and monitors and responds to node and pod failures.
• Components include the API server, controller manager, scheduler, and etcd.

3. Control Plane:

• The control plane is a set of components on the master node that collectively manages the cluster.
• Key components: API Server, etcd, Controller Manager, and Scheduler.

4. Pod:

• The smallest deployable units in Kubernetes.
• A pod represents a single instance of a running process in a cluster.
• A pod can contain one or more containers that are tightly coupled and share the same network namespace, storage, and specifications.

5. Namespace:

• A way to divide cluster resources between multiple users or projects.
• Namespaces provide a scope for names, making it easier to organize and isolate resources within a cluster.

6. Service:

• An abstraction that defines a logical set of pods and a policy by which to access them.
• Services enable communication between different parts of an application, or between applications.

7. ReplicaSet:

• Ensures that a specified number of replicas (instances) of a pod are running at all times.
• Provides scaling and high availability for pods.

8. Deployment:

• Manages the deployment and scaling of a set of pods.
• Provides declarative updates to applications, allowing you to describe the desired state for your deployed containers.

9. ConfigMap and Secret:

• ConfigMap holds configuration data as key-value pairs.
• Secret holds sensitive information, such as passwords or API keys.

10. Kubelet:

• The primary "node agent" that runs on each node.
• Ensures that containers are running in a Pod.

11. Kube Proxy:

• Maintains network rules on nodes.
• Enables communication to Pods from network sessions inside or outside the cluster.

12. StorageClass and PersistentVolume:

• StorageClass defines different classes of storage.
• PersistentVolume represents a piece of storage in the cluster.

13. Ingress:

• Manages external access to services within a cluster.
• Provides HTTP and HTTPS routing to services based on rules.

14. RBAC (Role-Based Access Control):

• Defines what actions are allowed or denied for different users or systems within a cluster.

15. ClusterRole and ClusterRoleBinding:

• Similar to RBAC but applies at the cluster level.

Understanding these concepts is crucial for effectively deploying, managing, and scaling applications in a Kubernetes cluster. The architecture and flexibility of Kubernetes provide a robust platform for container orchestration and application management.