flashcards software cloud

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Open-source container-orchestration system for automating computer application deployment, scaling, and management.

It aims to provide a "platform for automating deployment, scaling, and operations of application containers across clusters of hosts". It works with a range of container tools and runs containers in a cluster, often with images built using Docker.

• In Docker swarms you have:
  • a docker master
  • and you have docker workers
• In a Kubernetes replication set you have:
  • a master
  • nodes

Kubernetes is a container orchestrator to provision, manage, and scale apps. You can use it to manage the lifecycle of containerized apps in a cluster of nodes, which is a collection of worker machines such as VMs or physical machines.

Your apps might need many other resources to run, such as volumes, networks, and secrets that can help you connect to databases, talk to firewalled back ends, and secure keys. With Kubernetes, you can add those resources into your app. Infrastructure resources that your apps need are managed declaratively.

The key paradigm of Kubernetes is its declarative model. You provide the state that you want and Kubernetes makes it happen. If you need five instances, you don't start five separate instances on your own. Instead, you tell Kubernetes that you need five instances, and Kubernetes automatically reconciles the state. If something goes wrong with one of your instances and it fails, Kubernetes still knows the state that you want and creates instances on an available node.

Control Plane:

• API Server
  • Scheduling
  • REST Services
    • Scheduler
    • etcd
      • Replication Controllers
• A replica is a series of pods - all of these are handled by the replication controller
  • This happens by contacting the API server
• etcd controls the state of K8s.
  • It tells K8s what node is available, etc.
  • Distributed Consistent and Watchable key-value store
• A YAML - fed to the master - defines the desired state of the K8s system.
• Master controls Nodes
  • Master schedules Pods to run inside Nodes.

What is a Kubernetes replication set?

• I suppose it's the equivalent of a Docker Swarm

A Volume may span multiple VMs or maybe multiple datacenters In Kubernetes we don't really talk about VMs but rather about Nodes

• Applications based on Heroku vs Kubernetes: https://www.fairwinds.com/blog/heroku-vs.-kubernetes-the-big-differences-you-should-know

• https://www.ibm.com/cloud/architecture/content/course/kubernetes-101/