Kubernetes, often abbreviated as K8s, is an open-source platform designed to automate the deployment, scaling, and operations of application containers across clusters of hosts. Here's a comprehensive look at Kubernetes:
History
- Kubernetes was originally developed by Google, drawing heavily from Google's experience with managing containers at scale, known as Borg.
- The project was open-sourced in 2014 under the Cloud Native Computing Foundation (CNCF), which promotes and sustains open-source technologies for cloud computing.
- Since its inception, Kubernetes has seen rapid adoption and has become the de facto standard for container orchestration.
Core Components
- Master Components: These manage the cluster. They include:
- API Server: The front-end for the Kubernetes control plane.
- etcd: A distributed key-value store that stores all cluster data.
- Controller Manager: Runs controller processes for managing nodes, replication, and endpoints.
- Scheduler: Watches for newly created pods with no assigned node and selects a node for them to run on.
- Node Components: Each node in the cluster runs these components:
- Kubelet: An agent that runs on each node and ensures that containers are running in a pod.
- Kube-proxy: Maintains network rules on nodes, allowing network communication to your pods.
- Container Runtime: Software that runs containers, like Docker or containerd.
Key Features
- Automatic Binpacking: Automatically places containers based on resource requirements and constraints, while not sacrificing availability.
- Self-Healing: Restarts containers that fail, replaces and reschedules containers when nodes die, kills containers that don't respond to health checks, and doesn't advertise them to clients until they are ready.
- Horizontal Scaling: Scales applications up or down with simple commands, with the ability to update the underlying image or configuration.
- Service Discovery and Load Balancing: Exposes containers using DNS names or their own IP addresses, and load balances across them.
- Automated Rollouts and Rollbacks: Kubernetes gradually rolls out changes to your application or its configuration, while monitoring application health to ensure it doesn't kill all your instances at the same time.
Use Cases
- Managing microservices in a cloud-native environment.
- Deploying and scaling web applications or APIs.
- Facilitating DevOps practices by providing consistent environments for development, testing, and production.
- Handling batch jobs or scheduled tasks efficiently.
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