Kubernetes is an open-source container orchestration platform for automating deployment, scaling, and management of containerized applications. It was originally designed and developed by Google and open-sourced in 2014, now managed by the Cloud Native Computing Foundation (CNCF).
Core Concepts
The core concepts of Kubernetes include:
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Pod: The smallest deployable unit in Kubernetes. A Pod can contain one or more containers that share network and storage resources.
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Node: A worker machine in the cluster, which can be a physical machine or a virtual machine. Each Node runs a container runtime (like Docker), kubelet, and kube-proxy.
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Cluster: A collection of multiple Nodes, which is the pool of computing resources managed by Kubernetes.
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Service: Defines access policies for a set of Pods and provides stable network endpoints, even if Pod IP addresses change.
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Deployment: Manages declarative updates for Pods and ReplicaSets, supporting rolling updates and rollbacks.
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ConfigMap: Used to store non-sensitive configuration data, which can be mounted into Pods or used as environment variables.
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Secret: Used to store sensitive information such as passwords, OAuth tokens, and SSH keys.
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Namespace: Used to create multiple virtual clusters within the same cluster for resource isolation.
How It Works
Kubernetes uses a master-slave architecture:
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Control Plane: Responsible for decision-making and responding to cluster events, including API Server, Scheduler, Controller Manager, and etcd.
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Worker Node: Runs containerized applications, including kubelet, kube-proxy, and container runtime.
Key Features
- Automated deployment and rollback: Supports declarative configuration, automatically implementing application deployment and updates.
- Service discovery and load balancing: Automatically assigns IPs and DNS names to containers, implementing load balancing.
- Auto-scaling: Automatically adjusts the number of Pods based on CPU usage or other metrics.
- Self-healing: Automatically restarts failed containers, replaces nodes, and reschedules Pods.
- Storage orchestration: Automatically mounts storage systems such as local storage and cloud storage.
Use Cases
Kubernetes is widely used in microservices architecture, CI/CD pipelines, big data processing, machine learning, and other scenarios, serving as the standard platform for cloud-native applications.